552
Brain Research, 172 (1979) 552-556 © Elsevier/North-Holland Biomedical Press
Selective resistance of sensory cells of the mesencephalic trigeminal nucleus to kainic acid-induced lesions
M. COLONNIER, M. STERIADE* and P. L A N D R Y
Laboratoires de Neurobiologie, HOpital de l'Enfant JOsus, Pavillon Notre-Dame, 2075 Ave de VitrO, Qudbec, GIJ 5B3 and the Ddpartement d'Anatomie, Universitd Laval and (M.S. and P.L.) Laboratoire de Neurophysiologie, Ddpartement de Physiologie, Facuhd de Mddecine, Universitd Laval, Qudbec G1K 7P4 (Canada)
(Accepted May 5th, 1979)
There is increasing evidence that all neurons are not equally affected by injections of kainic acid, a glutamic acid analog with powerful neurotoxic effects. Several studies have shown that neurons of hippocampal fields CA1-CA2 and of the fascia dentata are less sensitive than those of CA3-CA4 to intraventricular s, intrastriata111 or intra-amygdaloid I injections of kainic acid. The granule cells of the fascia dentata, however, are destroyed by kainate injections into the hippocampal formation 8. Cerebellar granule cells are spared beyond a radius of 0.3 mm of the center of an injection site but degenerate within this radius 7. Some neurons of unidentified type within the magnocellular periventricular hypothalamic nucleus survive after a diencephalic injection of kainic acid 9. The demonstration of an absolute resistance to kainic acid of a homogenous cell group with well-defined morphological features and physiological properties would shed light on the mechanisms of kainic acid toxicity. Here we report that the unipolar cells of the mesencephalic trigeminal nucleus have a completely normal appearance within a kainic acid-induced midbrain tegmental lesion causing total loss of all other neuronal types. This was a chance observation made during experiments designed to investigate the effects of kainic acid-induced excitation and subsequent lesion of midbrain reticular neurons upon states of vigilance (in preparation). Adult cats were chronically implanted with guide cannulae into the superficial layers of the superior colliculi. Several days later, the kainic acid solution was injected into the dorsal or middle part of the central tegmental field (FTC 2) of unanesthetized, non-paralyzed animals maintained through a painless device in a stereotaxic apparatus. The animals received uni- or bilateral injections of the kainic acid solution (0.25-2.5 #g, dissolved in all cases in 1/zl of phosphate buffer). The injections lasted 5 min (two animals) or 20 min (7 animals) and the needle was taken out 5 min after the * To whom correspondence should be addressed.
553
(Legend on following page)
554 end o f the injection. Ten to 15 days after the injections, the animals were anesthetized a n d perfused i n t r a c a r d i a l l y with formalin. F r o z e n sections o f 20-40 # m were stained with thionine or cresyl violet. Fig. 1 is a p h o t o m i c r o g r a p h o f the medial h a l f o f a kainic acid lesion o f the m i d b r a i n , showing a complete d i s a p p e a r a n c e o f neurons a n d a massive gliosis in the deep layers o f the s u p e r i o r colliculus a n d the reticular f o r m a t i o n . The extent a n d severity o f the p a t h o l o g i c a l changes can be evaluated by c o m p a r i n g with the non-injected opposite side (Fig. 2). The lesion invades the lateral p o r t i o n o f the central gray. A g r o u p o f the large n e u r o n s o f the mesencephalic t r i g e m i n a l nucleus, lying at the j u n c t i o n o f the central gray a n d o f the reticular f o r m a t i o n are seen to survive within the p a t h o l o g i c a l area. This is m o r e obvious in Fig. 3 where the same g r o u p o f cells is
Fig. 1. Medial portion of a kainic acid (2.5/~g in 1 pl) induced lesion of the midbrain showing surviving neurons of the trigeminal mesencephalic nucleus at the junction of the central gray and ot the reticular formation. SC: superior colliculus; CG : central gray ; RF: reticular formation. Calibraticn bar in/~m: Nissl stain. Fig. 2. Same area of midbrain from the non-injected opposite side. Abbreviations as in Fig. 1. Fig. 3. Some of the surviving neurons of Fig. 1 at higher magnifications. Fig. 4. Normal neurons of the trigeminal mesencephalic nucleus from the non-injected opposite side at the same magnification as Fig. 3. Figs. 5 and 6. Surviving neurons of the trigeminal mesencephalic nucleus within the necrotic center of a large kainic acid (2.5 ,ug/cd) lesion in another preparation, at different magnifications. Abbreviations as in Fig. 1.
555 clearly seen to lie in a region where other neurons have completely disappeared and where the number of glial cells is considerably increased (compare with normal side, Fig. 4). No differences can be seen between the surviving trigeminal neurons within the lesion and those of the opposite side, even at the highest optical magnification (compare insets in Figs. 3 and 4). The resistance of the trigeminal neurons was found in all injected animals. Moreover, in the case of a few injections, and for yet unknown reasons, the lesion had a relatively large necrotic center, encompassing the mesencephalic nucleus (Fig. 5). Even in these circumstances, the cells of the trigeminal nucleus survive within the necrotic tissue (Fig. 6), and although some mechanical distortion can perhaps be suspected, the internal details of many cells do not differ from the normal (Fig. 6 inset). The preservation of trigeminal nucleus cells is obviously not ascribable to poor penetration of kainic acid due to tissue barrier interfaces within the midbrain, as neurons located medially, dorsally, laterally and ventrally, belonging to the central gray, deep collicular layers and reticular formation completely disappeared. One of the hypotheses concerning the mechanism by which kainic acid leads to neuronal death is that it induces excessive, prolonged depolarization of neurons 1°. If so, the survival of the cells of the trigeminal nucleus suggests that they would not be depolarized by glutamate. This nucleus contains the cell bodies of sensory neurons analogous to those found in dorsal root and cranial nerve sensory ganglia a,4. There is evidence that intra-arterially administered L-glutamic acid does not depolarize the cells of dorsal root 6 and vagal nodose 5 ganglia. More directly relevant to the present data, it was found that iontophoretically applied glutamate or kainate fails to activate the cells of the mesencephalic trigeminal nucleus in the rat (De Montigny and Lund, personal communication). These pharmacological observations and our morphological findings taken together support the suggestion 10 that the neurotoxic effects of kainic acid are indeed a consequence of an excitatory action on glutamic acid receptors. However, the continued presence of the cells within the necrotic center of some lesions (as in Figs. 5 and 6) leads us to believe that these cells may possess other resistance factors, possibly of a more general metabolic nature, ensuring their survival. The authors wish to thank Denis Drolet, Jacques Rodrigue and Jean Colonnier for their technical help and photographic assistance. This work was supported by grants from the Medical Research Council of Canada to M.C. (MA-3735) and M.S. (MT-3689).
1 Ben-Ari, Y., Lagowska, J., Tremblay, E. and Le Gal La Salle, G., A new model of focal status epilepticus: intra-amygdaloid application of kainic acid elicits repetitive secondarily generalized convulsive seizures, Brain Research, 163 (1979) 176-179. 2 Berman, A., The Brain Stem o f the Cat, The University of Wisconsin Press, Madison-MilwaukeeLondon, 1968, pp. 175. 3 Brown, J. O., The nuclear pattern of the non-tectal portions of the midbrain and isthmus in the dog and cat, J. comp. Neurol., 78 (1943) 365-405. 4 Dault, S. H. and Smith, R. D., A quantitative study of the nucleus of the mesencephalic tract of the trigeminal nerve of the cat, J. eomp. Neurol., 165 (1969) 79-88.
556 5 De Groat, W. C., GABA-depolarization of a sensory ganglion: antagonism by picrotoxin and bicuculline, Brain Research, 38 (1972) 429432. 6 De Groat, W. C., Lalley, P. M. and Saum, W. R., :Depolarization of dorsal root ganglia in the cat by GABA and related amino acids: antagonism by picrotoxin and bicuculline, Brain Research, 44 (1972) 273-277. 7 Herndon, R. M. and Coyle, J. T., Glutamergic innervation, kainic acid, and selective vulnerability in the cerebellum. In E. G. McGeer, J. W. Olney and P. L. McGeer (Eds.), Kainic A c i d a s a Tool in Neurobiology, Raven Press, New York, 1978, pp. 219-237. 8 Nadler, J. V., Perry, B. W. and Cotman, C. W., Preferential vulnerability of hippocampus to intraventricular kainic acid. In E. G. McGeer, J. W. Olney and P. L. McGeer (Eds.), Kainic Acid as a Tool in Neurobiology, Raven Press, New York, 1978, pp. 219-237. 9 0 l n e y , J. W. and Gubareff, T., Extreme selectivity of olfactory cortical neurons to kainic acid toxicity. In E. G. McGeer, J. W. Olney and P. L. McGeer (Eds.), Kainic A c i d a s a Toolin Neurobiology, Raven Press, New York, 1978, pp. 201-217. 10 Olney, J. W., Rhee, V. and Ho, O. L., Kainic acid: a powerful neurotoxic analogue of glutamate, Brain Research, 77 (1974) 507-512. 11 Wuerthele, S. M., Lovell, K. L., Jones, M. Z. and Moore, K. E., A histological study of kainic a:id-induced lesions in the rat brain, Brain Research, 149 (1978) 489-497.
Brain Research, 172 (1979) 552-556 © Elsevier/North-Holland Biomedical Press
Selective resistance of sensory cells of the mesencephalic trigeminal nucleus to kainic acid-induced lesions
M. COLONNIER, M. STERIADE* and P. L A N D R Y
Laboratoires de Neurobiologie, HOpital de l'Enfant JOsus, Pavillon Notre-Dame, 2075 Ave de VitrO, Qudbec, GIJ 5B3 and the Ddpartement d'Anatomie, Universitd Laval and (M.S. and P.L.) Laboratoire de Neurophysiologie, Ddpartement de Physiologie, Facuhd de Mddecine, Universitd Laval, Qudbec G1K 7P4 (Canada)
(Accepted May 5th, 1979)
There is increasing evidence that all neurons are not equally affected by injections of kainic acid, a glutamic acid analog with powerful neurotoxic effects. Several studies have shown that neurons of hippocampal fields CA1-CA2 and of the fascia dentata are less sensitive than those of CA3-CA4 to intraventricular s, intrastriata111 or intra-amygdaloid I injections of kainic acid. The granule cells of the fascia dentata, however, are destroyed by kainate injections into the hippocampal formation 8. Cerebellar granule cells are spared beyond a radius of 0.3 mm of the center of an injection site but degenerate within this radius 7. Some neurons of unidentified type within the magnocellular periventricular hypothalamic nucleus survive after a diencephalic injection of kainic acid 9. The demonstration of an absolute resistance to kainic acid of a homogenous cell group with well-defined morphological features and physiological properties would shed light on the mechanisms of kainic acid toxicity. Here we report that the unipolar cells of the mesencephalic trigeminal nucleus have a completely normal appearance within a kainic acid-induced midbrain tegmental lesion causing total loss of all other neuronal types. This was a chance observation made during experiments designed to investigate the effects of kainic acid-induced excitation and subsequent lesion of midbrain reticular neurons upon states of vigilance (in preparation). Adult cats were chronically implanted with guide cannulae into the superficial layers of the superior colliculi. Several days later, the kainic acid solution was injected into the dorsal or middle part of the central tegmental field (FTC 2) of unanesthetized, non-paralyzed animals maintained through a painless device in a stereotaxic apparatus. The animals received uni- or bilateral injections of the kainic acid solution (0.25-2.5 #g, dissolved in all cases in 1/zl of phosphate buffer). The injections lasted 5 min (two animals) or 20 min (7 animals) and the needle was taken out 5 min after the * To whom correspondence should be addressed.
553
(Legend on following page)
554 end o f the injection. Ten to 15 days after the injections, the animals were anesthetized a n d perfused i n t r a c a r d i a l l y with formalin. F r o z e n sections o f 20-40 # m were stained with thionine or cresyl violet. Fig. 1 is a p h o t o m i c r o g r a p h o f the medial h a l f o f a kainic acid lesion o f the m i d b r a i n , showing a complete d i s a p p e a r a n c e o f neurons a n d a massive gliosis in the deep layers o f the s u p e r i o r colliculus a n d the reticular f o r m a t i o n . The extent a n d severity o f the p a t h o l o g i c a l changes can be evaluated by c o m p a r i n g with the non-injected opposite side (Fig. 2). The lesion invades the lateral p o r t i o n o f the central gray. A g r o u p o f the large n e u r o n s o f the mesencephalic t r i g e m i n a l nucleus, lying at the j u n c t i o n o f the central gray a n d o f the reticular f o r m a t i o n are seen to survive within the p a t h o l o g i c a l area. This is m o r e obvious in Fig. 3 where the same g r o u p o f cells is
Fig. 1. Medial portion of a kainic acid (2.5/~g in 1 pl) induced lesion of the midbrain showing surviving neurons of the trigeminal mesencephalic nucleus at the junction of the central gray and ot the reticular formation. SC: superior colliculus; CG : central gray ; RF: reticular formation. Calibraticn bar in/~m: Nissl stain. Fig. 2. Same area of midbrain from the non-injected opposite side. Abbreviations as in Fig. 1. Fig. 3. Some of the surviving neurons of Fig. 1 at higher magnifications. Fig. 4. Normal neurons of the trigeminal mesencephalic nucleus from the non-injected opposite side at the same magnification as Fig. 3. Figs. 5 and 6. Surviving neurons of the trigeminal mesencephalic nucleus within the necrotic center of a large kainic acid (2.5 ,ug/cd) lesion in another preparation, at different magnifications. Abbreviations as in Fig. 1.
555 clearly seen to lie in a region where other neurons have completely disappeared and where the number of glial cells is considerably increased (compare with normal side, Fig. 4). No differences can be seen between the surviving trigeminal neurons within the lesion and those of the opposite side, even at the highest optical magnification (compare insets in Figs. 3 and 4). The resistance of the trigeminal neurons was found in all injected animals. Moreover, in the case of a few injections, and for yet unknown reasons, the lesion had a relatively large necrotic center, encompassing the mesencephalic nucleus (Fig. 5). Even in these circumstances, the cells of the trigeminal nucleus survive within the necrotic tissue (Fig. 6), and although some mechanical distortion can perhaps be suspected, the internal details of many cells do not differ from the normal (Fig. 6 inset). The preservation of trigeminal nucleus cells is obviously not ascribable to poor penetration of kainic acid due to tissue barrier interfaces within the midbrain, as neurons located medially, dorsally, laterally and ventrally, belonging to the central gray, deep collicular layers and reticular formation completely disappeared. One of the hypotheses concerning the mechanism by which kainic acid leads to neuronal death is that it induces excessive, prolonged depolarization of neurons 1°. If so, the survival of the cells of the trigeminal nucleus suggests that they would not be depolarized by glutamate. This nucleus contains the cell bodies of sensory neurons analogous to those found in dorsal root and cranial nerve sensory ganglia a,4. There is evidence that intra-arterially administered L-glutamic acid does not depolarize the cells of dorsal root 6 and vagal nodose 5 ganglia. More directly relevant to the present data, it was found that iontophoretically applied glutamate or kainate fails to activate the cells of the mesencephalic trigeminal nucleus in the rat (De Montigny and Lund, personal communication). These pharmacological observations and our morphological findings taken together support the suggestion 10 that the neurotoxic effects of kainic acid are indeed a consequence of an excitatory action on glutamic acid receptors. However, the continued presence of the cells within the necrotic center of some lesions (as in Figs. 5 and 6) leads us to believe that these cells may possess other resistance factors, possibly of a more general metabolic nature, ensuring their survival. The authors wish to thank Denis Drolet, Jacques Rodrigue and Jean Colonnier for their technical help and photographic assistance. This work was supported by grants from the Medical Research Council of Canada to M.C. (MA-3735) and M.S. (MT-3689).
1 Ben-Ari, Y., Lagowska, J., Tremblay, E. and Le Gal La Salle, G., A new model of focal status epilepticus: intra-amygdaloid application of kainic acid elicits repetitive secondarily generalized convulsive seizures, Brain Research, 163 (1979) 176-179. 2 Berman, A., The Brain Stem o f the Cat, The University of Wisconsin Press, Madison-MilwaukeeLondon, 1968, pp. 175. 3 Brown, J. O., The nuclear pattern of the non-tectal portions of the midbrain and isthmus in the dog and cat, J. comp. Neurol., 78 (1943) 365-405. 4 Dault, S. H. and Smith, R. D., A quantitative study of the nucleus of the mesencephalic tract of the trigeminal nerve of the cat, J. eomp. Neurol., 165 (1969) 79-88.
556 5 De Groat, W. C., GABA-depolarization of a sensory ganglion: antagonism by picrotoxin and bicuculline, Brain Research, 38 (1972) 429432. 6 De Groat, W. C., Lalley, P. M. and Saum, W. R., :Depolarization of dorsal root ganglia in the cat by GABA and related amino acids: antagonism by picrotoxin and bicuculline, Brain Research, 44 (1972) 273-277. 7 Herndon, R. M. and Coyle, J. T., Glutamergic innervation, kainic acid, and selective vulnerability in the cerebellum. In E. G. McGeer, J. W. Olney and P. L. McGeer (Eds.), Kainic A c i d a s a Tool in Neurobiology, Raven Press, New York, 1978, pp. 219-237. 8 Nadler, J. V., Perry, B. W. and Cotman, C. W., Preferential vulnerability of hippocampus to intraventricular kainic acid. In E. G. McGeer, J. W. Olney and P. L. McGeer (Eds.), Kainic Acid as a Tool in Neurobiology, Raven Press, New York, 1978, pp. 219-237. 9 0 l n e y , J. W. and Gubareff, T., Extreme selectivity of olfactory cortical neurons to kainic acid toxicity. In E. G. McGeer, J. W. Olney and P. L. McGeer (Eds.), Kainic A c i d a s a Toolin Neurobiology, Raven Press, New York, 1978, pp. 201-217. 10 Olney, J. W., Rhee, V. and Ho, O. L., Kainic acid: a powerful neurotoxic analogue of glutamate, Brain Research, 77 (1974) 507-512. 11 Wuerthele, S. M., Lovell, K. L., Jones, M. Z. and Moore, K. E., A histological study of kainic a:id-induced lesions in the rat brain, Brain Research, 149 (1978) 489-497.
