Brain Research, 95 (1975) 265-279 © Elsevier Scientific Publishing Company, Amsterdam - Printed in The Netherlands
265
T R A N S G A N G L I O N I C D E G E N E R A T I O N IN T R I G E M I N A L P R I M A R Y SENSORY N E U R O N S
G U N N A R G R A N T AND J A N A R V I D S S O N
Department of Anatomy, Karolinska lnstitutet, S-10401 Stockholm 60 (Sweden)
SUMMARY
In 16 kittens either the frontal or the inferior alveolar nerve was transected and in 17 adult rats either the supraorbital, the infraorbital or the mental nerve was divided. The postoperative survival periods were kept at 3-28 days for the kittens and 15-26 days for the rats. Sections from the caudal brain stem and the upper part of the cervical cord were impregnated according to the Fink-Heimer method, procedure II. In the kittens degeneration was found after the 8th postoperative day ipsilaterally in both the spinal and main sensory trigeminal nuclei and the spinal trigeminal tract. In the rats degeneration was found in all cases in the same ipsilateral structures as in the kittens. The amount of degeneration was relatively great in the rats, whereas it was very modest in the kittens. A somatotopical pattern was found for the degeneration both within the spinal and the main sensory nuclei. It was in agreement with what has been found in earlier studies, where other techniques have been used. By a comparison with the results of a previous study on the trigeminal nerve in the rat, where partial lesions of the ganglia had been made, it was found that the degeneration in the present study did not cover the whole area receiving primary trigeminal afferents. Possible explanations for this are discussed.
INTRODUCTION
In previous studies it was shown that degeneration of axons projecting from the hypoglossal and from lower lumbar spinal motor nerve cell groups can be brought about within the central nervous system of kittens by transection of peripheral nerves, and demonstrated with the aid of suppressive silver techniquell, 14. Such axonal degeneration was shown to be preceded by degeneration of the parent cell body 14. At an earlier stage this part of the neuron could be demonstrated, often with impregnated degenerating dendrites attachedlO, 14. Similar degeneration of axons and of parent cell bodies and dendrites could also be demonstrated in neurons whose axons
266 did not project outside the central nervous system, after lesions involving central nervous pathways 12,16. These findings were obviously based on a retrograde cellular reaction which had been strong enough in the young animals to result in irreversible changes, followed by degeneration*. The findings made it tempting to investigate whether or not degeneration could be brought about in centrally directed branches of primary sensory neurons, and demonstrated with suppressive silver technique after transection of peripheral branches of such neurons. This could be the case if peripheral nerve transection gives rise to retrograde cellular degeneration in the ganglion. A perusal of the literature showed that a loss of cells in spinal ganglia after peripheral nerve transections had been described by several investigators. Ranson 26, 27 and Cavanaugh 5 had made detailed studies of such cell loss after transections of peripheral nerves in rats. Furthermore, Cassirer 4 had described Marchi positive granules in the ipsilateral dorsal column and in the spinal gray substance along the course of dorsal root fibers, after transection of the sciatic nerve in rabbits. These granules, which were not very numerous were found to be most abundant at a stage when the maximal changes in the cells of the ganglia had already declined. Therefore, Cassirer favored the idea that the degeneration demonstrated with the Marchi method was secondary to cellular changes in the ganglia. This idea lends further support from an interesting report by Nageotte 24 in 1906. He studied, by the Marchi method, a case of degeneration of the intermediary nerve in man. A 36-year-old man, who had suffered from cancer of the stomach, developed a facial paralysis one month before death. A metastatic nucleus was found immediately below the geniculate ganglion. The facial nerve and the chorda tympani were found to be completely degenerated below the lesion, but, in addition, all the central portion of the fascicles of the intermediary nerve in the pons were seen to be degenerated. Since the geniculate ganglion was not primarily affected by the metastatic nucleus, the degeneration in the pons was interpreted as a secondary transcellular degeneration, following amputation of the peripheral portion of the axon very near the cell. Of interest in this connection are also the findings reported by Bochenek 1 in 1901. He found Marchi positive granules in substantial amounts in the spinal tract of the trigeminal nerve 50-60 days after evulsion of different branches of the trigeminal nerve in rabbits**. The granules were localized differently depending upon which nerve had been affected. The mental nerve
* Some general aspects of this type of degeneration have been discussed in a recent review articleTM. ** It could be argued that the evulsion of the nerves could have caused a primary affection of the trigeminal ganglion cells. The degeneration which was observed in the spinal trigeminal tract would then have been an ordinary secondary Wallerian degeneration and not have been secondary to a retrograde degeneration of ganglion cells. This alternative cannot be excluded, especially since Bochenek does not comment upon whether the ganglia were examined histologically or not. The fact that Marchi positive granules occurred in great amounts as late as 50-60 days after the operation does not speak in favor of it, however. Bochenek, furthermore, was of the opinion that the amount of degeneration was greater after 50-60 days than after 43 days, a postoperative period which had been used in another animal.
267 was found to be 'represented' dorsally, the frontal nerve ventrally and the infraorbital nerve in the region of the tract between the other two nerves. From these studies it seems that 'transganglionic' degeneration can occur in primary sensory neurons. If this kind of degeneration could be provoked in significant amounts in different parts of the nervous system and if it could also be demonstrated with methods showing axonal degeneration, it should be possible to use it as a tool in neuroanatomical research. It should then be possible to transect peripheral branches of different primary sensory neurons and map the distribution of the central branches in the central nervous system. The need for a more detailed knowledge of the central projections of different peripheral sensory nerves is obvious. In the spinal cord, for example, where a very exact knowledge exists regarding peripheral connections o f different motor nerve cell groups 29, even basic knowledge regarding the sensory side is still lacking. In a previous study labyrinthine nerves were severed in newborn rabbits 15. After 6-9 days postoperative survival degeneration was found in Nauta stained sections within the region of the vestibular nuclei known to receive primary vestibular fibers. Electron microscopy showed electron-dense changes of boutons and myelinated axons indicative of degeneration. Even though there was support for the opinion that there was no primary affection of the ganglia at the operation, definite conclusions could not be drawn. For the problem of transganglionic degeneration in primary sensory neurons, it could be argued, in addition, that the VIIIth nerve would not be comparable to other nerves due to the bipolar character of its neurons. Therefore the present study was undertaken in which transganglionic degeneration in trigeminal sensory neurons is demonstrated. MATERIAL AND METHODS
Seventeen kittens, 3-23 days old at operation, and 16 female young adult Sprague-Dawley rats, weighing 170-220 g (corresponding to ages between 8 and 9 weeks) at operation, were subjected to unilateral peripheral nerve transections (Tables I and II). In one additional rat the trigeminal root was transected completely just central to the ganglion, on the left side. The surgical procedures and the perfusions were made under intraperitoneal Mebumal anesthesia (3 mg/100 g body weight) in the case of the kittens and under chloral hydrate anesthesia (30 mg/100 g body weight) in the case of the rats. All nerve transections were made on the left side. They were made with the aid of a very small, sharp pair of scissors. Care was taken not to cause traction of the central stump of the nerve at the operation. The experimental situation is schematically illustrated in Fig. 1. In the kittens the frontal or the inferior alveolar nerve was transected (Table I). The frontal nerve was identified below the roof of the orbit a few millimeters behind the upper frontal margin of the orbit, after a horizontal incision through the skin. It was divided and a few millimeters of its distal portion were removed. The inferior alveolar nerve was identified at its entry into the mandibular canal after a
268
Nerv. ophtha[micus '
I. . . . . .
Nerv.maxillaris :Nerv'maxillar]s~¥~ )
',i .~" ~
~andibuG:i :eri
~ spinalis
" i principalis¥
[~ I'I Nucleus I111" '11 J-~ Jl spinaliskr
J[ Region for examination Fig. 1. Schematic drawing showing the experimental situation. In the kitten the frontal or the inferior alveolar nerve was transected (branches of the ophthalmic and the mandibular nerve, respectively). In the rat the supraorbital, infraorbital or mental nerve was transected (branches of the ophthalmic, maxillary and mandibular nerve, respectively).
vertical incision at the anterior margin of the masseter muscle and an opening in the mandible. The nerve was divided here and a few millimeters of its distal portion were removed. In the rats the supraorbital, the infraorbital or the mental nerve was divided (Table II). The supraorbital nerve was cut at the upper frontal margin of the orbit. The infraorbital and the mental nerves were identified and divided at their exits from the infraorbital and mental foramina, respectively. In all instances a few millimeters of the distal portions of the nerves were resected. After postoperative survival times varying between 3 and 28 days for the kittens (Table I) and between 15 and 26 days for the rats (Table If) the animals were anesthetized and perfused through the ascending aorta, first for about 15 sec with saline, and thereafter with 4 % buffered formaldehyde solution, as described by Holt and Hicks 18, but with a sucrose content of 5% instead of 7.5% (see ref. 34). The perfusion solutions were kept at room temperature. The brain with the trigeminal ganglia attached was dissected free immediately after the perfusion and placed in the fixative solution for further fixation. Blocks were then prepared from the lower part of the brain stem and the upper part of the cervical cord. They were cut on the freezing microtome in serial sections at 20/~m. Most of the kitten material was cut in horizontal sections. The remaining material from kittens and the whole material from rats were cut at transverse sections. The frozen sections were collected in groups of 5 (horizontal sections) or 10 (transverse sections). At least one section from each group was stained with silver according to procedure I[ of Fink and Heimer s. In a few instances sections which had been prepared in this way were bleached and poststained with cresyl violet, according to the method described by Kawamura and Niimi 19. The trigeminal ganglia were taken care of separately for later studies.
269
Fig. 2. Photomicrographs showing degeneration in the spinal trigeminal nucleus (a and b) and in the spinal tract (c) after peripheral nerve transections in the kitten. Fink-Heimer preparations. × 500. a : from the nucleus tractus spinalis trigemini oralis. Horizontal section. Note the 'dust-like' appearance of the degeneration. Inferior alveolar nerve transection; 21 days at operation; 20 days postoperative survival, b: from the nucleus tractus spinalis trigemini caudalis. Transverse section. Note impregnation of fiber fragments. Compare with a. Frontal nerve transection; 23 days at operation; 24 days postoperative survival, c: from the tractus spinalis and the nucleus tractus spinalis caudalis (left). Horizontal section. Note a small number of impregnated fiber fragments. Impregnated capillary wall, oriented in parallel to the fibers of the tract is seen at lower left. Inferior alveolar nerve transection; 21 days at operation; 23 days postoperative survival. RESULTS
Kitten In the kitten material, degenerating fibers were found on the side of the operation both in the spinal trigeminal tract and in its nucleus. In addition, some degeneration was observed in the caudal part of the main sensory nucleus. The amount of degeneration in all these structures was extremely modest (cf. Fig. 2c). N o degeneration was found before the 8th postoperative day (see Table I). The impression was gained that the amount of degeneration was somewhat greater in those kittens which had been operated on at the age of 21 and 23 days than in the younger kittens. In these older kittens it seemed, furthermore, that the character of the degeneration was somewhat different after the shortest postoperative survival periods compared with later stages (see Table I). In the two kittens which had survived for 16 and 20 days the degeneration picture had a finely granular appearance suggestive of F i n k Heimer terminal 'dust' (Fig. 2a) and it was only later that irregularly shaped fiber fragments appeared (cf. Fig. 2b). After transection of the inferior alveolar nerve the degeneration was found to be localized in the dorsal part of the spinal trigeminal nucleus, whereas transection of the frontal nerve gave rise to degeneration in its ventral part. Caudally the degeneration was found to extend into the rostral part of the subnucleus caudalis of Olszewski ~5 but not as far as the first cervical segment.
27O TABLE I DEGENERATION IN THE
KITTEN MATERIAL FOLLOWING TRANSECTION OF PERIPHERAL BRANCHES OF THE
TRIGEMINAL NERVE
Age at operation (days)
Postoperative survival (days)
3 3 3 5 7 9 9 23 3 3 5 5 21 21 21 21 21
10 14 17 7 3 11 14 24 10 16 6 8 16 20 23 24 28
Transected nerve Frontal nerve
lnferior alveolar nerve
+ + + + + + + + + + -]+ ÷ + q+ ~-
Degeneration in spinal tract and/or spinal tract nucleus
+ + + 0 0 + + + + + 0 -t-~ -)qt
T A B L E II THE RAT MATERIAL WITH DEGENERATIONIN ALL CASES FOLLOWINGTRANSECTION OF PERIPHERAL BRANCHES OF THE TRIGEMINAL NERVE
Case
Transectednerve Supraorbital nerve
TR9 T R 10 T R 11 T R 12 T R 13 T R 14 T R 15 T R 16 T R 17 TR5 T R 18 TR 6 TR 7 T R 19 TR 8 T R 20
Infraorbital nerve
Mental nerve
+ + + + + + -I+ -]+ + + -]÷ -t+
Postoperative survival (days)
15 18 22 26 15 18 22 26 15 16 18 19 22 22 25 26
Fig. 3. Photomicrographs from transverse sections of the nucleus tractus spinalis trigemini caudalis of the rat, showing degeneration in two cases after transection of peripheral nerves. Lateral above, dorsal left. Fink-Heimer preparations. Twenty-two days postoperative survival. a and b: from corresponding areas of the nucleus tractus spinalis caudalis in the two cases. Note the different localizations of the degeneration. Infraorbital nerve transection (a); mental nerve transection (b). x 180. c and d: details from the areas with degeneration in a and b, respectively at higher magnification. X 300.
272
Rat Degeneration was found on the side o f the operation in the spinal and main sensory nuclei in all rats. It is to be noticed, however, that there was no rat with a shorter postoperative survival period than 15 days (Table II). The a m o u n t o f degeneration in the nuclei was rather impressive (Figs. 3 and 4a), in striking contrast to the situation in the kittens. The degeneration which was observed in the spinal tract, in which most o f the fibers had been cut transversely was, however, much less impressive than in the nuclei. The gelatinous substance seemed to be free from degeneration, except for fibers penetrating from the spinal tract into deeper parts of the spinal nucleus (cJl Fig. 3a and b with Fig. 4b). Degeneration was found, regardless o f which nerve branch had been divided, both in the spinal and in the main sensory nuclei (Fig. 5). Within these nuclei the degeneration was distributed differently, however, depending upon which o f the 3
Fig. 4. a: photomicrograph from a transverse section through the main sensory trigeminal nucleus of a rat, showing degeneration after transection of the mental nerve; 15 days postoperative survival. Fink-Heimer preparation, posttreated according to the Kawamura and Niimi TM method, x 300. b: photomicrograph from a transverse section through the nucleus tractus spinalis trigemini caudalis of a rat, showing degeneration two days after transection of the trigeminal nerve central to the Gasserian ganglion. Lateral above, dorsal left. Note the small impregnated granules (degenerating terminals; , 1 ~,~=~CAU DAL
/l/ N.t r.sp.V~+~
s
Fig. 5. Drawings of transverse sections from the sensory trigeminal nuclear complex of the rat, slightly modified after Torvik33, showing the distribution of degeneration within the spinal and main sensory nuclei after peripheral nerve transections, The degeneration in the spinal tract has not been indicated. Filled circles, crosses and open circles indicate degeneration following transection of the mental, the infraorbital and the supraorbital nerve, respectively. (For abbreviations see pp. 277-278). nerve b r a n c h e s h a d been transected. A f t e r t r a n s e c t i o n o f the m e n t a l nerve the deg e n e r a t i o n was f o u n d in the d o r s a l p a r t o f the nuclei (Fig. 5; cf also Fig. 3b). Division o f the i n f r a o r b i t a l nerve resulted in d e g e n e r a t i o n j u s t ventral to this a r e a (Fig. 5;
274
cf also Fig. 3a). Transection of the supraorbital nerve finally gave rise to degeneration extremely ventrally within the nuclei (Fig. 5: 2,7). Within the spinal nucleus the degeneration extended from the rostral pole and caudally to the rostral level of the pyramidal decussation, after transections of the mental and infraorbital nerves (Fig. 5: 7,2). The degeneration following supraorbital nerve transection, on the other hand, was found to be localized in the caudal part of the nucleus, from the level of the pyramidal decussation (Fig. 5: 2) and further caudally, down to the first cervical segment, but not further down. The degeneration following division of the infraorbital nerve covered a larger field in the nuclei, both in the dorsoventral and in rostrocaudal directions, than the degeneration found after transection of the supraorbital or the mental nerves (Fig. 5). The smallest area was covered by the degeneration found after transection of the supraorbital nerve (Fig. 5: 2,7). DISCUSSION
Even though the ganglia have not been investigated yet, the most reasonable conclusion from the present findings will be that the degeneration observed has been secondary to a retrograde degeneration of ganglion cells, following transection of the peripheral nerves. The findings confirm and extend observations from investigations made around the turn of this century. Bochenek 1, in 1901, found somatotopically localized degeneration in the spinal trigeminal tract, by the Marchi method after evulsion of peripheral branches of the trigeminal nerve in rabbits* *. Darkschewitsch 7, in 1892, and Cassirer 4, in 1899, described degeneration in the dorsal column and in the dorsal horn along the course o f dorsal root fibers in Marchi material from the guinea pig and the rabbit, respectively, after transection of the sciatic nerve. Nageotte z4, in 1906, found degeneration in Marchi preparations along the central course of the intermediary nerve in the pons of a patient who had suffered from cancer of the stomach and developed a facial paralysis one month before death. A metastatic nucleus was found to have caused a lesion of the VIIth nerve just below the geniculate ganglion. Observations of a corresponding character had been made even earlier. In cases of amputation of limbs, both in experimental animals (for example see ref. 28 and also ref. 4) and in man 9 degeneration had been found in the dorsal columns, in Marchi stained material. Flatau 9, who described the degeneration in man had examined the spinal cord of a patient who had died 3 months after amputation of the left leg. He found degeneration not only of dorsal column fibers on the affected side but also of dorsal root collaterals in the spinal gray substance on the same side. In these early studies the degeneration was demonstrated with the aid of the Marchi method. This permits the demonstration of degenerating myelin sheaths, but not of degenerating axons and axonal arborizations. In the present study degeneration has been shown with the Fink-Heimer method, which permits the demonstration ** See footnote to p. 266.
275 of degenerating axons and axonal ramifications, including terminal boutons. Degenerating fibers (axons) were found not only in the spinal trigeminal tract in both the kitten and the rat material (cf. Fig. 2c), but also in the spinal and main sensory nuclei (cf. Figs. 2b, 3 and 4a). This means that not only parent fibers, but also smaller branches have been impregnated. Pictures like those illustrated in Fig. 2a indicate, furthermore, that even terminal axonal structures may have been impregnated. The amount of degeneration seen in the Fink-Heimer preparations was very modest in the kitten material, in contrast to the situation in the rat where it was relatively great. This difference was somewhat surprising. A reverse situation would rather have been expected, because the retrograde reaction to axonal trauma seems to be more pronounced in young animals than in adult onesS, z2,2a. It could be explained on the basis of a species difference, but there could also be other explanations. The reaction of the ganglion cells may in fact have been very pronounced in the kittens, even still more than in the rats, but the majority of the degenerating fibers have had a character at this rather early developmental stage that made them less favorable for demonstration with the Fink-Heimer method. Another possibility could be that the postoperative survival times for the kittens were not optimal. Future studies of the ganglia and possibly also additional material covering a broader spectrum of postoperative survival periods, may help to solve this problem. The fact that transection of peripheral nerves very far distally could give rise to degeneration in the central nervous system of an amount that was found in the rat material was quite unexpected. It is generally believed that the more peripheral a transection of an axon is made, the weaker is the retrograde cellular reaction (see, for example, ref. 23). The 3 nerves which were examined were the supraorbital, the infraorbital and the mental nerves (Table II). They were all transected very far peripherally, at their exits from the orbit, the infraorbital and the mental foramina, respectively. This is worth noting. In the studies commented on above 1,4,7,24, the nerve lesions were localized much closer to the ganglia. The same was true in the study on the vestibular nerve in the newborn rabbit 15. A somatotopical pattern was found in the distribution of the degeneration in the present study both in the kitten and in the rat. This was demonstrated most easily in the rat where the brain stem had been cut in transverse sections and the amount of degeneration was relatively great. Here the degeneration found after transection of the mental nerve was localized dorsally both in the spinal and in the main sensory nuclei (Figs. 3b and 5: 2,7). The degeneration which was found after transection of the infraorbital and supraorbital nerves was localized successively more ventrally within the nuclei (Fig. 5; see also Fig. 3a). This somatotopical pattern agrees well with what has been found in earlier studies by other techniques, in different animal speciesl,2,8,Zl, 33. It has been shown that the ophthalmic, maxillary and mandibular divisions of the trigeminal nerve are represented in the reverse order from dorsally to ventrally, both within the spinal and main sensory nuclei and in the spinal trigeminal tract (cf. Fig. 6). The situation seems to be similar in man (see, for example, ref. 32). The area of distribution for the degeneration along the rostrocaudal axis of the
276 ros~rat
"1
"
-\;"
"
r.f.XlI
/~ I
'
I
~,
",
N.m.V
- - " Sr.~
d.m'." / N.i.pV
~EV-
-N.p -'-_s ~
8
oo
}
~, ~ ~.,.~__ N - ~ ' . ' ~:'.-.-..-...~
// f
.
.- ~ :3-'-N.
~o
'
N.
t~l,'.'7.:,t:{ ~l,~rFt2t#.'i+.g/
~,~co,,,; ~
i
-
j&:v.:. • .~.k ~
•
o\
/
~
~
'~D~(t,"
~{t
\1
L~;,,-,
N.o.V
/-'!,-!
-~
ii I
,'4 I
~:-:': TR 37 1111f11*. ° TR 81 .\\'~'+~+ TR 67
-~ ~
I
/-
--i
f
Fig. 6. Fig. 2 from the study by Torvik 33, showing the distribution of Wallerian degeneration in the spinal and main sensory trigeminal nuclei, the spinal trigeminal tract and in the solitary tract and its nucleus, after partial lesions of the Gasserian ganglion in three rats, TR 37, TR 81 and TR 67, representing the mandibular, ophthalmic and maxillary divisions of the trigeminal nerve, respectively. (For abbreviations see pp. 277-278) (From J. comp. Neurol., by courtesy of the Publishers.)
sensory nuclei did not cover the whole receiving area for primary trigeminal afferents. This seems to be true both for the kitten and the rat. In the kitten no degeneration was found to extend caudally into the cervical segments, although it is known that primary trigeminal afferents terminate in the upper cervical segments, especially in the first cervical segment, in the adult cat (see, for example, ref. 20). The situation in
..~,
277 the rat appears f r o m a comparison o f Fig. 5, which illustrates the findings f r o m the present study, with Fig. 6, which is an illustration f r o m the publication by Torvik aa showing the distribution o f degeneration after partial lesions o f the Gasserian ganglion in the rat. In Fig. 6 it is seen that degeneration extends caudally into the second cervical segment, whereas in Fig. 5 this segment is free f r o m degeneration. The m o s t caudal level at which degeneration was f o u n d in the rat in the present study was the first cervical segment. Here degeneration appeared after transection o f the supraorbital nerve. The reason why the whole area receiving primary trigeminal afferents was not covered by degeneration in the present study could be that the transections did not include all branches o f the 3 divisions o f the Vth nerve. A n o t h e r explanation could be that the peripheral transections did n o t result in transganglionic degeneration in all those neurons, whose peripheral branches had been transected. Finally, the postoperative survival times which were used m a y have been unsuitable for the demonstration o f some degenerating fibers by the silver m e t h o d that was used. One circumstance which could speak in favor o f the last 2 possibilities is the fact that the gelatinous substance seemed to be free f r o m degeneration, except for fibers penetrating f r o m the spinal tract into deeper parts o f the spinal nucleus (Fig. 3), although it is k n o w n that the gelatinous substance receives primary afferents f r o m the Vth nerve, also in the rat 3z (cf. Fig. 4b)*. Future studies, including transections o f other branches o f the Vth nerve than those investigated in the present study, examinations o f the ganglia, a wider spectrum o f postoperative survival times and maybe also other silver techniques, can be hoped to solve these problems. ACKNOWLEDGEMENTS This w o r k was supported by the Swedish Medical Research Council, Project B75-12X-553-11A.
ABBREVIATIONS Br.c. -C.n. = C.r. = Dec.pyr. = d.m. = D.v.n. F.s. G. VII G.n. M.v.n.
= = = = =
brachium conjunctivum cuneate nucleus corpus restiforme decussatio pyramidum nucleus dorsomedialis of Astrrm descending vestibular nucleus solitary tract genu of facial nerve gracile nucleus medial vestibular nucleus
N.V. VII, = X, XII, N.caud. V = N.c.e. N.com
= =
N.f.s. N.int.
= =
motor nuclei of Vth, VIIth, Xth and XIIth cranial nerves nucleus caudalis of spinal Vth nucleus external cuneate nucleus nucleus commissuralis of Cajal nucleus of solitary tract nucleus intermedius of Cajal
* It is of interest in this connection that transection of the infraorbital nerve and other branches of the Vth nerve has been demonstrated to result in somatotopically localized loss of acid phosphatase activity in the gelatinous substance of the rat a0. From early studies with partial lesions of the Gasserian ganglional it is well known that there is a somatotopical organization of primary trigeminal afferents in the substantia gelatinosa of the cat. This was confirmed in a study on rat 83.
278 N.i.p.V.
--
N.m.V. N.o.V.
-~-
N.pr.V.
::
N.r.1. N.s.V. N.tr.sp.V. =
nucleus interpolaris of spinal Vth nucleus mesencephalic Vth nucleus nucleus oralis of spinal Vth nucleus main sensory nucleus (nucleus principalis) lateral reticular nucleus nucleus supratrigeminalis of Lorentede N6 nucleus of spinal Vth tract
Ol.inf. Ol.s. Pyr. R.f.
-~ ~--
r.f.V, Xll : s.g.
-
Tr.sp.V.
:~-
inferior olive superior olive pyramis dorsolateral part of reticular formation efferent fibers of Vth and XlIth cranial nerves substantia gelatinosa of dorsal horn and nucleus caudalis spinal Vthtract
REFERENCES 1 BOCHENEK, A., La racine bulbo-spinale du trijumeau et ses connexions avec les trois branches p6riph6riques, N~vraxe, 3 (1901) 109-119. 2 BREGMAN,E., Ueber experimentelle aufsteigende Degeneration motorischer und sensibler Hirnnerven, Arb. neurol. Inst. Univ. Wien, 1 (1892) 73-97. 3 BRODAL, A., Modification of Gudden method for study of cerebral localization, Arch. Neurol. (Chic.), 43 (1940) 46-58. 4 CASSIRER,R., Ueber Ver/inderungen der Spinalganglienzellen und ihrer centralen Forts~itze nach Durchschneidung der zugeh6rigen peripheren Nerven, Dtsch. Z. Nervenheilk., 14 0899) 150166. 5 CAVANAUGH,M. W., Quantitative effects of the peripheral innervation area on nerves and spinal ganglion cells, J. comp. NeuroL, 94 (1951) 181-220. 6 DARIAN-SMITH,l., AND MAYDAY,G., Somatotopic organization within the brain-stem trigeminal complex of the cat, Exp. Neurol., 2 (1960) 290-309. 7 DARKSCHEWITSCH, L., Ueber die Ver/inderungen in den centralen Abschnitt eines motorischen Nerven bei Verletzung des peripheren Abschnittes, Neurol. Cbl., 11 (1892) 658-668. 8 FINK, R. P., AND HEIMER, L., Two methods for selective silver impregnation of degenerating axons and their synaptic endings in the central nervous system, Brain Research, 4 (1967) 369-374. 9 FLATAU, E., Ueber Veranderungen des menschlichen R/.ickenmarks nach Wegfall gr6sserer Gliedmaassen, Dtsch. reed. Wschr., 18 (1897) 278-279. l0 GRANT, G., Degenerative changes in dendrites following axonal transection, Experientia (Basel), 21 (1965) 722. l l GRANT, G., Silver impregnation of degenerating dendrites, cells and axons central to axonal transection, lI. A Nauta study on spinal motor neurones in kittens, Exp. Brain Res., 6 0968) 284-293. 12 GRANT, G., Neuronal changes central to the site of axon transection. A method for the identification of retrograde changes in perikarya, dendrites and axons by silver impregnation. In W. J. H. NAUTA AND S. O. E. EaBESSON (Eds.), Contemporary Research Methods in Neuroanatomy, Springer, Berlin, 1970, pp. 173-185. 13 GRANT, G., Retrograde neuronal degeneration. In M. SANTINI (Ed.), Golgi Centennial Symposium: Perspectives in Neurobiology, Raven Press, New York, 1975, pp. 195-200. 14 GRANT, G., AND ALDSKOGIUS,H., Silver impregnation of degenerating dendrites, cells and axons central to axonal transection. I. A Nauta study on the hypoglossal nerve in kittens, Exp. Brain Res., 3 (1967) 150-162. 15 GRANT, G., EKVALL,L., AND WESTMAN,J., Transganglionic degeneration in the vestibular nerve. In J. STAHLE(Ed.), Vestibular Function on Earth and in Space, Wenner-Gren Symposium No. 15, Pergamon Press, Oxford, 1970, pp. 301-305. 16 GRANT, G., AND WESTMAN, J., The lateral cervical nucleus in the cat. IV. A light and electron microscopical study after midbrain lesions with demonstration of indirect Wallerian degeneration at the ultrastructural level, Exp. Brain Res., 7 (1969) 51-67. 17 HEIMER, L., AND WALL, P. D., The dorsal root distribution to the substantia gelatinosa of the rat with a note on the distribution in the cat, Exp. Brain Res., 6 (1968) 89-99. 18 HOLT, S. J., AND HICKS, R. M., Studies on formalin fixation for electron microscopy and cytochemical staining purposes, J. biophys, biochem. Cytol., 11 (1961) 31-45.
279 19 KAWAMURA, S., AND NIIMI, K., Counterstaining of Nauta-Gygax impregnated sections with cresyl violet, Stain. Technol., 47 (1972) 1-6. 20 KERR, F. W. L., Structural relation of the trigeminal spinal tract to upper roots and the solitary nucleus in the cat, Exp. Neurol., 4 (1961) 134-148. 21 KERR, F. W. L., The divisional organization of afferent fibres of the trigeminal nerve, Brain, 86 (1963) 721-732. 22 LA VELLE, A., AND LA VELLE, F. W., Neuronal swelling and chromatolysis as influenced by the state of cell development, Amer. J. Anat., 102 (1958) 219-241. 23 LIEBERMAN,A. R., Some factors affecting retrograde neuronal responses to axonal lesions, In P. BELLAIRSAND E. G. GRAY (Eds.), Essays on the Nervous System. A Festschrift for Professor J. Z. Young, Clarendon Press, Oxford, 1974, pp. 71-105. 24 NAGEOTTE, J., The pars intermedia or nervus intermedius of Wrisberg, and the bulbo-pontine gustatory nucleus in man, Rev. Neurol. Psychiat., 4 (1906) 473488. 25 OLSZEWSKI,J., On the anatomical and functional organization of the spinal trigeminal nucleus, J. comp. Neurol., 92 (1950) 401413. 26 RANSON, S. W., Retrograde degeneration in the spinal nerves, J. comp. Neurol., 16 (1906) 265293. 27 RANSON,S. W., Alterations in the spinal ganglion cells following neurotomy, J. comp. Neurol., 19 (1909) 125-153. 28 REDLICH, E., Die Pathologie der tabischen Hinterstrangserkrankung, Fischer, Jena, 1897. 29 ROMANES,G. J., Motor localization and the effects of nerve injury on the ventral horn cells of the spinal cord, J. Anat. (Lond.), 80 (1946) 117-131. 30 RUSTIONI,A., SANYAL,S., AND KUYPERS, H. G. J. M., A histochemical study of the distribution of the trigeminal divisions in the substantia gelatinosa of the rat, Brain Research, 32 (1971) 45-52. 31 SZENT.~GOTHAI,J., AND KISS, T., Projection of dermatomes on the substantia gelatinosa, Arch. NeuroL Psychiat. (Chic.), 62 (1949) 734-744. 32 TAREN, J. A., The positions of the cutaneous components of the facial glossopharyngeal and vagal nerves in the spinal tract of V, J. comp. Neurol., 122 (1964) 389-397. 33 TORVIK, A., Afferent connections to the sensory trigeminal nuclei, the nucleus of the solitary tract and adjacent structures. An experimental study in the rat, J. comp. Neurol., 106 (1956) 51-142. 34 WESTMAN,J., The lateral cervical nucleus in the cat. II. An electron microscopical study of the normal structure, Brain Research, 11 (1968) 107-123.
265
T R A N S G A N G L I O N I C D E G E N E R A T I O N IN T R I G E M I N A L P R I M A R Y SENSORY N E U R O N S
G U N N A R G R A N T AND J A N A R V I D S S O N
Department of Anatomy, Karolinska lnstitutet, S-10401 Stockholm 60 (Sweden)
SUMMARY
In 16 kittens either the frontal or the inferior alveolar nerve was transected and in 17 adult rats either the supraorbital, the infraorbital or the mental nerve was divided. The postoperative survival periods were kept at 3-28 days for the kittens and 15-26 days for the rats. Sections from the caudal brain stem and the upper part of the cervical cord were impregnated according to the Fink-Heimer method, procedure II. In the kittens degeneration was found after the 8th postoperative day ipsilaterally in both the spinal and main sensory trigeminal nuclei and the spinal trigeminal tract. In the rats degeneration was found in all cases in the same ipsilateral structures as in the kittens. The amount of degeneration was relatively great in the rats, whereas it was very modest in the kittens. A somatotopical pattern was found for the degeneration both within the spinal and the main sensory nuclei. It was in agreement with what has been found in earlier studies, where other techniques have been used. By a comparison with the results of a previous study on the trigeminal nerve in the rat, where partial lesions of the ganglia had been made, it was found that the degeneration in the present study did not cover the whole area receiving primary trigeminal afferents. Possible explanations for this are discussed.
INTRODUCTION
In previous studies it was shown that degeneration of axons projecting from the hypoglossal and from lower lumbar spinal motor nerve cell groups can be brought about within the central nervous system of kittens by transection of peripheral nerves, and demonstrated with the aid of suppressive silver techniquell, 14. Such axonal degeneration was shown to be preceded by degeneration of the parent cell body 14. At an earlier stage this part of the neuron could be demonstrated, often with impregnated degenerating dendrites attachedlO, 14. Similar degeneration of axons and of parent cell bodies and dendrites could also be demonstrated in neurons whose axons
266 did not project outside the central nervous system, after lesions involving central nervous pathways 12,16. These findings were obviously based on a retrograde cellular reaction which had been strong enough in the young animals to result in irreversible changes, followed by degeneration*. The findings made it tempting to investigate whether or not degeneration could be brought about in centrally directed branches of primary sensory neurons, and demonstrated with suppressive silver technique after transection of peripheral branches of such neurons. This could be the case if peripheral nerve transection gives rise to retrograde cellular degeneration in the ganglion. A perusal of the literature showed that a loss of cells in spinal ganglia after peripheral nerve transections had been described by several investigators. Ranson 26, 27 and Cavanaugh 5 had made detailed studies of such cell loss after transections of peripheral nerves in rats. Furthermore, Cassirer 4 had described Marchi positive granules in the ipsilateral dorsal column and in the spinal gray substance along the course of dorsal root fibers, after transection of the sciatic nerve in rabbits. These granules, which were not very numerous were found to be most abundant at a stage when the maximal changes in the cells of the ganglia had already declined. Therefore, Cassirer favored the idea that the degeneration demonstrated with the Marchi method was secondary to cellular changes in the ganglia. This idea lends further support from an interesting report by Nageotte 24 in 1906. He studied, by the Marchi method, a case of degeneration of the intermediary nerve in man. A 36-year-old man, who had suffered from cancer of the stomach, developed a facial paralysis one month before death. A metastatic nucleus was found immediately below the geniculate ganglion. The facial nerve and the chorda tympani were found to be completely degenerated below the lesion, but, in addition, all the central portion of the fascicles of the intermediary nerve in the pons were seen to be degenerated. Since the geniculate ganglion was not primarily affected by the metastatic nucleus, the degeneration in the pons was interpreted as a secondary transcellular degeneration, following amputation of the peripheral portion of the axon very near the cell. Of interest in this connection are also the findings reported by Bochenek 1 in 1901. He found Marchi positive granules in substantial amounts in the spinal tract of the trigeminal nerve 50-60 days after evulsion of different branches of the trigeminal nerve in rabbits**. The granules were localized differently depending upon which nerve had been affected. The mental nerve
* Some general aspects of this type of degeneration have been discussed in a recent review articleTM. ** It could be argued that the evulsion of the nerves could have caused a primary affection of the trigeminal ganglion cells. The degeneration which was observed in the spinal trigeminal tract would then have been an ordinary secondary Wallerian degeneration and not have been secondary to a retrograde degeneration of ganglion cells. This alternative cannot be excluded, especially since Bochenek does not comment upon whether the ganglia were examined histologically or not. The fact that Marchi positive granules occurred in great amounts as late as 50-60 days after the operation does not speak in favor of it, however. Bochenek, furthermore, was of the opinion that the amount of degeneration was greater after 50-60 days than after 43 days, a postoperative period which had been used in another animal.
267 was found to be 'represented' dorsally, the frontal nerve ventrally and the infraorbital nerve in the region of the tract between the other two nerves. From these studies it seems that 'transganglionic' degeneration can occur in primary sensory neurons. If this kind of degeneration could be provoked in significant amounts in different parts of the nervous system and if it could also be demonstrated with methods showing axonal degeneration, it should be possible to use it as a tool in neuroanatomical research. It should then be possible to transect peripheral branches of different primary sensory neurons and map the distribution of the central branches in the central nervous system. The need for a more detailed knowledge of the central projections of different peripheral sensory nerves is obvious. In the spinal cord, for example, where a very exact knowledge exists regarding peripheral connections o f different motor nerve cell groups 29, even basic knowledge regarding the sensory side is still lacking. In a previous study labyrinthine nerves were severed in newborn rabbits 15. After 6-9 days postoperative survival degeneration was found in Nauta stained sections within the region of the vestibular nuclei known to receive primary vestibular fibers. Electron microscopy showed electron-dense changes of boutons and myelinated axons indicative of degeneration. Even though there was support for the opinion that there was no primary affection of the ganglia at the operation, definite conclusions could not be drawn. For the problem of transganglionic degeneration in primary sensory neurons, it could be argued, in addition, that the VIIIth nerve would not be comparable to other nerves due to the bipolar character of its neurons. Therefore the present study was undertaken in which transganglionic degeneration in trigeminal sensory neurons is demonstrated. MATERIAL AND METHODS
Seventeen kittens, 3-23 days old at operation, and 16 female young adult Sprague-Dawley rats, weighing 170-220 g (corresponding to ages between 8 and 9 weeks) at operation, were subjected to unilateral peripheral nerve transections (Tables I and II). In one additional rat the trigeminal root was transected completely just central to the ganglion, on the left side. The surgical procedures and the perfusions were made under intraperitoneal Mebumal anesthesia (3 mg/100 g body weight) in the case of the kittens and under chloral hydrate anesthesia (30 mg/100 g body weight) in the case of the rats. All nerve transections were made on the left side. They were made with the aid of a very small, sharp pair of scissors. Care was taken not to cause traction of the central stump of the nerve at the operation. The experimental situation is schematically illustrated in Fig. 1. In the kittens the frontal or the inferior alveolar nerve was transected (Table I). The frontal nerve was identified below the roof of the orbit a few millimeters behind the upper frontal margin of the orbit, after a horizontal incision through the skin. It was divided and a few millimeters of its distal portion were removed. The inferior alveolar nerve was identified at its entry into the mandibular canal after a
268
Nerv. ophtha[micus '
I. . . . . .
Nerv.maxillaris :Nerv'maxillar]s~¥~ )
',i .~" ~
~andibuG:i :eri
~ spinalis
" i principalis¥
[~ I'I Nucleus I111" '11 J-~ Jl spinaliskr
J[ Region for examination Fig. 1. Schematic drawing showing the experimental situation. In the kitten the frontal or the inferior alveolar nerve was transected (branches of the ophthalmic and the mandibular nerve, respectively). In the rat the supraorbital, infraorbital or mental nerve was transected (branches of the ophthalmic, maxillary and mandibular nerve, respectively).
vertical incision at the anterior margin of the masseter muscle and an opening in the mandible. The nerve was divided here and a few millimeters of its distal portion were removed. In the rats the supraorbital, the infraorbital or the mental nerve was divided (Table II). The supraorbital nerve was cut at the upper frontal margin of the orbit. The infraorbital and the mental nerves were identified and divided at their exits from the infraorbital and mental foramina, respectively. In all instances a few millimeters of the distal portions of the nerves were resected. After postoperative survival times varying between 3 and 28 days for the kittens (Table I) and between 15 and 26 days for the rats (Table If) the animals were anesthetized and perfused through the ascending aorta, first for about 15 sec with saline, and thereafter with 4 % buffered formaldehyde solution, as described by Holt and Hicks 18, but with a sucrose content of 5% instead of 7.5% (see ref. 34). The perfusion solutions were kept at room temperature. The brain with the trigeminal ganglia attached was dissected free immediately after the perfusion and placed in the fixative solution for further fixation. Blocks were then prepared from the lower part of the brain stem and the upper part of the cervical cord. They were cut on the freezing microtome in serial sections at 20/~m. Most of the kitten material was cut in horizontal sections. The remaining material from kittens and the whole material from rats were cut at transverse sections. The frozen sections were collected in groups of 5 (horizontal sections) or 10 (transverse sections). At least one section from each group was stained with silver according to procedure I[ of Fink and Heimer s. In a few instances sections which had been prepared in this way were bleached and poststained with cresyl violet, according to the method described by Kawamura and Niimi 19. The trigeminal ganglia were taken care of separately for later studies.
269
Fig. 2. Photomicrographs showing degeneration in the spinal trigeminal nucleus (a and b) and in the spinal tract (c) after peripheral nerve transections in the kitten. Fink-Heimer preparations. × 500. a : from the nucleus tractus spinalis trigemini oralis. Horizontal section. Note the 'dust-like' appearance of the degeneration. Inferior alveolar nerve transection; 21 days at operation; 20 days postoperative survival, b: from the nucleus tractus spinalis trigemini caudalis. Transverse section. Note impregnation of fiber fragments. Compare with a. Frontal nerve transection; 23 days at operation; 24 days postoperative survival, c: from the tractus spinalis and the nucleus tractus spinalis caudalis (left). Horizontal section. Note a small number of impregnated fiber fragments. Impregnated capillary wall, oriented in parallel to the fibers of the tract is seen at lower left. Inferior alveolar nerve transection; 21 days at operation; 23 days postoperative survival. RESULTS
Kitten In the kitten material, degenerating fibers were found on the side of the operation both in the spinal trigeminal tract and in its nucleus. In addition, some degeneration was observed in the caudal part of the main sensory nucleus. The amount of degeneration in all these structures was extremely modest (cf. Fig. 2c). N o degeneration was found before the 8th postoperative day (see Table I). The impression was gained that the amount of degeneration was somewhat greater in those kittens which had been operated on at the age of 21 and 23 days than in the younger kittens. In these older kittens it seemed, furthermore, that the character of the degeneration was somewhat different after the shortest postoperative survival periods compared with later stages (see Table I). In the two kittens which had survived for 16 and 20 days the degeneration picture had a finely granular appearance suggestive of F i n k Heimer terminal 'dust' (Fig. 2a) and it was only later that irregularly shaped fiber fragments appeared (cf. Fig. 2b). After transection of the inferior alveolar nerve the degeneration was found to be localized in the dorsal part of the spinal trigeminal nucleus, whereas transection of the frontal nerve gave rise to degeneration in its ventral part. Caudally the degeneration was found to extend into the rostral part of the subnucleus caudalis of Olszewski ~5 but not as far as the first cervical segment.
27O TABLE I DEGENERATION IN THE
KITTEN MATERIAL FOLLOWING TRANSECTION OF PERIPHERAL BRANCHES OF THE
TRIGEMINAL NERVE
Age at operation (days)
Postoperative survival (days)
3 3 3 5 7 9 9 23 3 3 5 5 21 21 21 21 21
10 14 17 7 3 11 14 24 10 16 6 8 16 20 23 24 28
Transected nerve Frontal nerve
lnferior alveolar nerve
+ + + + + + + + + + -]+ ÷ + q+ ~-
Degeneration in spinal tract and/or spinal tract nucleus
+ + + 0 0 + + + + + 0 -t-~ -)qt
T A B L E II THE RAT MATERIAL WITH DEGENERATIONIN ALL CASES FOLLOWINGTRANSECTION OF PERIPHERAL BRANCHES OF THE TRIGEMINAL NERVE
Case
Transectednerve Supraorbital nerve
TR9 T R 10 T R 11 T R 12 T R 13 T R 14 T R 15 T R 16 T R 17 TR5 T R 18 TR 6 TR 7 T R 19 TR 8 T R 20
Infraorbital nerve
Mental nerve
+ + + + + + -I+ -]+ + + -]÷ -t+
Postoperative survival (days)
15 18 22 26 15 18 22 26 15 16 18 19 22 22 25 26
Fig. 3. Photomicrographs from transverse sections of the nucleus tractus spinalis trigemini caudalis of the rat, showing degeneration in two cases after transection of peripheral nerves. Lateral above, dorsal left. Fink-Heimer preparations. Twenty-two days postoperative survival. a and b: from corresponding areas of the nucleus tractus spinalis caudalis in the two cases. Note the different localizations of the degeneration. Infraorbital nerve transection (a); mental nerve transection (b). x 180. c and d: details from the areas with degeneration in a and b, respectively at higher magnification. X 300.
272
Rat Degeneration was found on the side o f the operation in the spinal and main sensory nuclei in all rats. It is to be noticed, however, that there was no rat with a shorter postoperative survival period than 15 days (Table II). The a m o u n t o f degeneration in the nuclei was rather impressive (Figs. 3 and 4a), in striking contrast to the situation in the kittens. The degeneration which was observed in the spinal tract, in which most o f the fibers had been cut transversely was, however, much less impressive than in the nuclei. The gelatinous substance seemed to be free from degeneration, except for fibers penetrating from the spinal tract into deeper parts of the spinal nucleus (cJl Fig. 3a and b with Fig. 4b). Degeneration was found, regardless o f which nerve branch had been divided, both in the spinal and in the main sensory nuclei (Fig. 5). Within these nuclei the degeneration was distributed differently, however, depending upon which o f the 3
Fig. 4. a: photomicrograph from a transverse section through the main sensory trigeminal nucleus of a rat, showing degeneration after transection of the mental nerve; 15 days postoperative survival. Fink-Heimer preparation, posttreated according to the Kawamura and Niimi TM method, x 300. b: photomicrograph from a transverse section through the nucleus tractus spinalis trigemini caudalis of a rat, showing degeneration two days after transection of the trigeminal nerve central to the Gasserian ganglion. Lateral above, dorsal left. Note the small impregnated granules (degenerating terminals; , 1 ~,~=~CAU DAL
/l/ N.t r.sp.V~+~
s
Fig. 5. Drawings of transverse sections from the sensory trigeminal nuclear complex of the rat, slightly modified after Torvik33, showing the distribution of degeneration within the spinal and main sensory nuclei after peripheral nerve transections, The degeneration in the spinal tract has not been indicated. Filled circles, crosses and open circles indicate degeneration following transection of the mental, the infraorbital and the supraorbital nerve, respectively. (For abbreviations see pp. 277-278). nerve b r a n c h e s h a d been transected. A f t e r t r a n s e c t i o n o f the m e n t a l nerve the deg e n e r a t i o n was f o u n d in the d o r s a l p a r t o f the nuclei (Fig. 5; cf also Fig. 3b). Division o f the i n f r a o r b i t a l nerve resulted in d e g e n e r a t i o n j u s t ventral to this a r e a (Fig. 5;
274
cf also Fig. 3a). Transection of the supraorbital nerve finally gave rise to degeneration extremely ventrally within the nuclei (Fig. 5: 2,7). Within the spinal nucleus the degeneration extended from the rostral pole and caudally to the rostral level of the pyramidal decussation, after transections of the mental and infraorbital nerves (Fig. 5: 7,2). The degeneration following supraorbital nerve transection, on the other hand, was found to be localized in the caudal part of the nucleus, from the level of the pyramidal decussation (Fig. 5: 2) and further caudally, down to the first cervical segment, but not further down. The degeneration following division of the infraorbital nerve covered a larger field in the nuclei, both in the dorsoventral and in rostrocaudal directions, than the degeneration found after transection of the supraorbital or the mental nerves (Fig. 5). The smallest area was covered by the degeneration found after transection of the supraorbital nerve (Fig. 5: 2,7). DISCUSSION
Even though the ganglia have not been investigated yet, the most reasonable conclusion from the present findings will be that the degeneration observed has been secondary to a retrograde degeneration of ganglion cells, following transection of the peripheral nerves. The findings confirm and extend observations from investigations made around the turn of this century. Bochenek 1, in 1901, found somatotopically localized degeneration in the spinal trigeminal tract, by the Marchi method after evulsion of peripheral branches of the trigeminal nerve in rabbits* *. Darkschewitsch 7, in 1892, and Cassirer 4, in 1899, described degeneration in the dorsal column and in the dorsal horn along the course o f dorsal root fibers in Marchi material from the guinea pig and the rabbit, respectively, after transection of the sciatic nerve. Nageotte z4, in 1906, found degeneration in Marchi preparations along the central course of the intermediary nerve in the pons of a patient who had suffered from cancer of the stomach and developed a facial paralysis one month before death. A metastatic nucleus was found to have caused a lesion of the VIIth nerve just below the geniculate ganglion. Observations of a corresponding character had been made even earlier. In cases of amputation of limbs, both in experimental animals (for example see ref. 28 and also ref. 4) and in man 9 degeneration had been found in the dorsal columns, in Marchi stained material. Flatau 9, who described the degeneration in man had examined the spinal cord of a patient who had died 3 months after amputation of the left leg. He found degeneration not only of dorsal column fibers on the affected side but also of dorsal root collaterals in the spinal gray substance on the same side. In these early studies the degeneration was demonstrated with the aid of the Marchi method. This permits the demonstration of degenerating myelin sheaths, but not of degenerating axons and axonal arborizations. In the present study degeneration has been shown with the Fink-Heimer method, which permits the demonstration ** See footnote to p. 266.
275 of degenerating axons and axonal ramifications, including terminal boutons. Degenerating fibers (axons) were found not only in the spinal trigeminal tract in both the kitten and the rat material (cf. Fig. 2c), but also in the spinal and main sensory nuclei (cf. Figs. 2b, 3 and 4a). This means that not only parent fibers, but also smaller branches have been impregnated. Pictures like those illustrated in Fig. 2a indicate, furthermore, that even terminal axonal structures may have been impregnated. The amount of degeneration seen in the Fink-Heimer preparations was very modest in the kitten material, in contrast to the situation in the rat where it was relatively great. This difference was somewhat surprising. A reverse situation would rather have been expected, because the retrograde reaction to axonal trauma seems to be more pronounced in young animals than in adult onesS, z2,2a. It could be explained on the basis of a species difference, but there could also be other explanations. The reaction of the ganglion cells may in fact have been very pronounced in the kittens, even still more than in the rats, but the majority of the degenerating fibers have had a character at this rather early developmental stage that made them less favorable for demonstration with the Fink-Heimer method. Another possibility could be that the postoperative survival times for the kittens were not optimal. Future studies of the ganglia and possibly also additional material covering a broader spectrum of postoperative survival periods, may help to solve this problem. The fact that transection of peripheral nerves very far distally could give rise to degeneration in the central nervous system of an amount that was found in the rat material was quite unexpected. It is generally believed that the more peripheral a transection of an axon is made, the weaker is the retrograde cellular reaction (see, for example, ref. 23). The 3 nerves which were examined were the supraorbital, the infraorbital and the mental nerves (Table II). They were all transected very far peripherally, at their exits from the orbit, the infraorbital and the mental foramina, respectively. This is worth noting. In the studies commented on above 1,4,7,24, the nerve lesions were localized much closer to the ganglia. The same was true in the study on the vestibular nerve in the newborn rabbit 15. A somatotopical pattern was found in the distribution of the degeneration in the present study both in the kitten and in the rat. This was demonstrated most easily in the rat where the brain stem had been cut in transverse sections and the amount of degeneration was relatively great. Here the degeneration found after transection of the mental nerve was localized dorsally both in the spinal and in the main sensory nuclei (Figs. 3b and 5: 2,7). The degeneration which was found after transection of the infraorbital and supraorbital nerves was localized successively more ventrally within the nuclei (Fig. 5; see also Fig. 3a). This somatotopical pattern agrees well with what has been found in earlier studies by other techniques, in different animal speciesl,2,8,Zl, 33. It has been shown that the ophthalmic, maxillary and mandibular divisions of the trigeminal nerve are represented in the reverse order from dorsally to ventrally, both within the spinal and main sensory nuclei and in the spinal trigeminal tract (cf. Fig. 6). The situation seems to be similar in man (see, for example, ref. 32). The area of distribution for the degeneration along the rostrocaudal axis of the
276 ros~rat
"1
"
-\;"
"
r.f.XlI
/~ I
'
I
~,
",
N.m.V
- - " Sr.~
d.m'." / N.i.pV
~EV-
-N.p -'-_s ~
8
oo
}
~, ~ ~.,.~__ N - ~ ' . ' ~:'.-.-..-...~
// f
.
.- ~ :3-'-N.
~o
'
N.
t~l,'.'7.:,t:{ ~l,~rFt2t#.'i+.g/
~,~co,,,; ~
i
-
j&:v.:. • .~.k ~
•
o\
/
~
~
'~D~(t,"
~{t
\1
L~;,,-,
N.o.V
/-'!,-!
-~
ii I
,'4 I
~:-:': TR 37 1111f11*. ° TR 81 .\\'~'+~+ TR 67
-~ ~
I
/-
--i
f
Fig. 6. Fig. 2 from the study by Torvik 33, showing the distribution of Wallerian degeneration in the spinal and main sensory trigeminal nuclei, the spinal trigeminal tract and in the solitary tract and its nucleus, after partial lesions of the Gasserian ganglion in three rats, TR 37, TR 81 and TR 67, representing the mandibular, ophthalmic and maxillary divisions of the trigeminal nerve, respectively. (For abbreviations see pp. 277-278) (From J. comp. Neurol., by courtesy of the Publishers.)
sensory nuclei did not cover the whole receiving area for primary trigeminal afferents. This seems to be true both for the kitten and the rat. In the kitten no degeneration was found to extend caudally into the cervical segments, although it is known that primary trigeminal afferents terminate in the upper cervical segments, especially in the first cervical segment, in the adult cat (see, for example, ref. 20). The situation in
..~,
277 the rat appears f r o m a comparison o f Fig. 5, which illustrates the findings f r o m the present study, with Fig. 6, which is an illustration f r o m the publication by Torvik aa showing the distribution o f degeneration after partial lesions o f the Gasserian ganglion in the rat. In Fig. 6 it is seen that degeneration extends caudally into the second cervical segment, whereas in Fig. 5 this segment is free f r o m degeneration. The m o s t caudal level at which degeneration was f o u n d in the rat in the present study was the first cervical segment. Here degeneration appeared after transection o f the supraorbital nerve. The reason why the whole area receiving primary trigeminal afferents was not covered by degeneration in the present study could be that the transections did not include all branches o f the 3 divisions o f the Vth nerve. A n o t h e r explanation could be that the peripheral transections did n o t result in transganglionic degeneration in all those neurons, whose peripheral branches had been transected. Finally, the postoperative survival times which were used m a y have been unsuitable for the demonstration o f some degenerating fibers by the silver m e t h o d that was used. One circumstance which could speak in favor o f the last 2 possibilities is the fact that the gelatinous substance seemed to be free f r o m degeneration, except for fibers penetrating f r o m the spinal tract into deeper parts o f the spinal nucleus (Fig. 3), although it is k n o w n that the gelatinous substance receives primary afferents f r o m the Vth nerve, also in the rat 3z (cf. Fig. 4b)*. Future studies, including transections o f other branches o f the Vth nerve than those investigated in the present study, examinations o f the ganglia, a wider spectrum o f postoperative survival times and maybe also other silver techniques, can be hoped to solve these problems. ACKNOWLEDGEMENTS This w o r k was supported by the Swedish Medical Research Council, Project B75-12X-553-11A.
ABBREVIATIONS Br.c. -C.n. = C.r. = Dec.pyr. = d.m. = D.v.n. F.s. G. VII G.n. M.v.n.
= = = = =
brachium conjunctivum cuneate nucleus corpus restiforme decussatio pyramidum nucleus dorsomedialis of Astrrm descending vestibular nucleus solitary tract genu of facial nerve gracile nucleus medial vestibular nucleus
N.V. VII, = X, XII, N.caud. V = N.c.e. N.com
= =
N.f.s. N.int.
= =
motor nuclei of Vth, VIIth, Xth and XIIth cranial nerves nucleus caudalis of spinal Vth nucleus external cuneate nucleus nucleus commissuralis of Cajal nucleus of solitary tract nucleus intermedius of Cajal
* It is of interest in this connection that transection of the infraorbital nerve and other branches of the Vth nerve has been demonstrated to result in somatotopically localized loss of acid phosphatase activity in the gelatinous substance of the rat a0. From early studies with partial lesions of the Gasserian ganglional it is well known that there is a somatotopical organization of primary trigeminal afferents in the substantia gelatinosa of the cat. This was confirmed in a study on rat 83.
278 N.i.p.V.
--
N.m.V. N.o.V.
-~-
N.pr.V.
::
N.r.1. N.s.V. N.tr.sp.V. =
nucleus interpolaris of spinal Vth nucleus mesencephalic Vth nucleus nucleus oralis of spinal Vth nucleus main sensory nucleus (nucleus principalis) lateral reticular nucleus nucleus supratrigeminalis of Lorentede N6 nucleus of spinal Vth tract
Ol.inf. Ol.s. Pyr. R.f.
-~ ~--
r.f.V, Xll : s.g.
-
Tr.sp.V.
:~-
inferior olive superior olive pyramis dorsolateral part of reticular formation efferent fibers of Vth and XlIth cranial nerves substantia gelatinosa of dorsal horn and nucleus caudalis spinal Vthtract
REFERENCES 1 BOCHENEK, A., La racine bulbo-spinale du trijumeau et ses connexions avec les trois branches p6riph6riques, N~vraxe, 3 (1901) 109-119. 2 BREGMAN,E., Ueber experimentelle aufsteigende Degeneration motorischer und sensibler Hirnnerven, Arb. neurol. Inst. Univ. Wien, 1 (1892) 73-97. 3 BRODAL, A., Modification of Gudden method for study of cerebral localization, Arch. Neurol. (Chic.), 43 (1940) 46-58. 4 CASSIRER,R., Ueber Ver/inderungen der Spinalganglienzellen und ihrer centralen Forts~itze nach Durchschneidung der zugeh6rigen peripheren Nerven, Dtsch. Z. Nervenheilk., 14 0899) 150166. 5 CAVANAUGH,M. W., Quantitative effects of the peripheral innervation area on nerves and spinal ganglion cells, J. comp. NeuroL, 94 (1951) 181-220. 6 DARIAN-SMITH,l., AND MAYDAY,G., Somatotopic organization within the brain-stem trigeminal complex of the cat, Exp. Neurol., 2 (1960) 290-309. 7 DARKSCHEWITSCH, L., Ueber die Ver/inderungen in den centralen Abschnitt eines motorischen Nerven bei Verletzung des peripheren Abschnittes, Neurol. Cbl., 11 (1892) 658-668. 8 FINK, R. P., AND HEIMER, L., Two methods for selective silver impregnation of degenerating axons and their synaptic endings in the central nervous system, Brain Research, 4 (1967) 369-374. 9 FLATAU, E., Ueber Veranderungen des menschlichen R/.ickenmarks nach Wegfall gr6sserer Gliedmaassen, Dtsch. reed. Wschr., 18 (1897) 278-279. l0 GRANT, G., Degenerative changes in dendrites following axonal transection, Experientia (Basel), 21 (1965) 722. l l GRANT, G., Silver impregnation of degenerating dendrites, cells and axons central to axonal transection, lI. A Nauta study on spinal motor neurones in kittens, Exp. Brain Res., 6 0968) 284-293. 12 GRANT, G., Neuronal changes central to the site of axon transection. A method for the identification of retrograde changes in perikarya, dendrites and axons by silver impregnation. In W. J. H. NAUTA AND S. O. E. EaBESSON (Eds.), Contemporary Research Methods in Neuroanatomy, Springer, Berlin, 1970, pp. 173-185. 13 GRANT, G., Retrograde neuronal degeneration. In M. SANTINI (Ed.), Golgi Centennial Symposium: Perspectives in Neurobiology, Raven Press, New York, 1975, pp. 195-200. 14 GRANT, G., AND ALDSKOGIUS,H., Silver impregnation of degenerating dendrites, cells and axons central to axonal transection. I. A Nauta study on the hypoglossal nerve in kittens, Exp. Brain Res., 3 (1967) 150-162. 15 GRANT, G., EKVALL,L., AND WESTMAN,J., Transganglionic degeneration in the vestibular nerve. In J. STAHLE(Ed.), Vestibular Function on Earth and in Space, Wenner-Gren Symposium No. 15, Pergamon Press, Oxford, 1970, pp. 301-305. 16 GRANT, G., AND WESTMAN, J., The lateral cervical nucleus in the cat. IV. A light and electron microscopical study after midbrain lesions with demonstration of indirect Wallerian degeneration at the ultrastructural level, Exp. Brain Res., 7 (1969) 51-67. 17 HEIMER, L., AND WALL, P. D., The dorsal root distribution to the substantia gelatinosa of the rat with a note on the distribution in the cat, Exp. Brain Res., 6 (1968) 89-99. 18 HOLT, S. J., AND HICKS, R. M., Studies on formalin fixation for electron microscopy and cytochemical staining purposes, J. biophys, biochem. Cytol., 11 (1961) 31-45.
279 19 KAWAMURA, S., AND NIIMI, K., Counterstaining of Nauta-Gygax impregnated sections with cresyl violet, Stain. Technol., 47 (1972) 1-6. 20 KERR, F. W. L., Structural relation of the trigeminal spinal tract to upper roots and the solitary nucleus in the cat, Exp. Neurol., 4 (1961) 134-148. 21 KERR, F. W. L., The divisional organization of afferent fibres of the trigeminal nerve, Brain, 86 (1963) 721-732. 22 LA VELLE, A., AND LA VELLE, F. W., Neuronal swelling and chromatolysis as influenced by the state of cell development, Amer. J. Anat., 102 (1958) 219-241. 23 LIEBERMAN,A. R., Some factors affecting retrograde neuronal responses to axonal lesions, In P. BELLAIRSAND E. G. GRAY (Eds.), Essays on the Nervous System. A Festschrift for Professor J. Z. Young, Clarendon Press, Oxford, 1974, pp. 71-105. 24 NAGEOTTE, J., The pars intermedia or nervus intermedius of Wrisberg, and the bulbo-pontine gustatory nucleus in man, Rev. Neurol. Psychiat., 4 (1906) 473488. 25 OLSZEWSKI,J., On the anatomical and functional organization of the spinal trigeminal nucleus, J. comp. Neurol., 92 (1950) 401413. 26 RANSON, S. W., Retrograde degeneration in the spinal nerves, J. comp. Neurol., 16 (1906) 265293. 27 RANSON,S. W., Alterations in the spinal ganglion cells following neurotomy, J. comp. Neurol., 19 (1909) 125-153. 28 REDLICH, E., Die Pathologie der tabischen Hinterstrangserkrankung, Fischer, Jena, 1897. 29 ROMANES,G. J., Motor localization and the effects of nerve injury on the ventral horn cells of the spinal cord, J. Anat. (Lond.), 80 (1946) 117-131. 30 RUSTIONI,A., SANYAL,S., AND KUYPERS, H. G. J. M., A histochemical study of the distribution of the trigeminal divisions in the substantia gelatinosa of the rat, Brain Research, 32 (1971) 45-52. 31 SZENT.~GOTHAI,J., AND KISS, T., Projection of dermatomes on the substantia gelatinosa, Arch. NeuroL Psychiat. (Chic.), 62 (1949) 734-744. 32 TAREN, J. A., The positions of the cutaneous components of the facial glossopharyngeal and vagal nerves in the spinal tract of V, J. comp. Neurol., 122 (1964) 389-397. 33 TORVIK, A., Afferent connections to the sensory trigeminal nuclei, the nucleus of the solitary tract and adjacent structures. An experimental study in the rat, J. comp. Neurol., 106 (1956) 51-142. 34 WESTMAN,J., The lateral cervical nucleus in the cat. II. An electron microscopical study of the normal structure, Brain Research, 11 (1968) 107-123.
