810

Specialia

(PST) s h o w i n g r e f r a c t o r y periods of 1 . 0 - i . 8 msec. I t s s h o r t l a t e n c y is also i n d i c a t i v e of its fibre-like n a t u r e . Moreover, n o s o m a t i c u n i t a r y responses were r e c o r d e d w h i c h were a s s o c i a t e d w i t h t h e e a r l y c o m p o n e n t . T h i s c o m p o n e n t m o s t likely reflects t h e a c t i v i t y of t h e relat i v e l y coarse fibres of Z u c k e r k a n d l ' s b u n d l e 10. I n t h i s p r o b e t h e n e g a t i v i t y (N) associated w i t h t h e s y n a p t i c a c t i v a t i o n of n D B B n e u r o n s a p p e a r s a t a d e p t h of 3000 ix. Here, t h e l a t e n c y t o p e a k is 7.5 msec. As t h e p r o b e d e s c e n d s t h e n e g a t i v i t y s t e a d i l y increases in a m p l i t u d e a n d decreases in p e a k l a t e n c y . A t 5000 ~, t h e p e a k n e g a t i v i t y h a s d e c r e a s e d t o 5.5 msec. T h e r e l a t i v e s t a b i l i t y of t h e p e a k l a t e n c y w i t h c h a n g e s in s t i m u l u s i n t e n s i t y (not shown) a n d r e l a t i v e s t a b i l i t y of t h e p e a k latency when recovering from paired-stimulus testing (PST) (see F i g u r e B) is a n i n d i c a t i o n of t h e m o n o s y n a p t i c n a t u r e of t h e N n e g a t i v i t y . T h e c o n d u c t i o n distance, for t h i s i n s t a n c e , was e s t i m a t e d t o b e a p p r o x i m a t e l y 6 ram. A c a l c u l a t e d c o n d u c t i o n v e l o c i t y for M F B fibres of 0 . 9 - 1 . 2 m / s e c s u p p o r t s t h e n o t i o n t h a t s u c h field r e s p o n s e s p r o b a b l y r e p r e s e n t t h e m o n o s y n a p t i c excitat i o n of cells. T h e t y p i c a l b e h a v i o r of t h e field r e s p o n s e w i t h P S T is i l l u s t r a t e d in F i g u r e B. R e c o r d s p e c i m e n s of t e s t responses f r o m 20 msec, 50 msec, a n d 100 msec i n t e r s t i m u l u s i n t e r vals (ISI) are p r e s e n t e d . T h e r e is no s u b s t a n t i a l r e c o v e r y in t h e 20 msec I S I , b u t t h e r e s p o n s e is a l m o s t c o m p l e t e l y r e c o v e r e d in t h e 50 msec I S I . A t 100 msec, t h e r e is a c t u a l l y a s l i g h t f a c i l i t a t i o n of t h e t e s t response. E x t r a c e l l u l a r u n i t a r y d i s c h a r g e s a p p e a r o u t of t h e n e g a t i v e e n v e l o p e (Figure C) of t h e field response. A f t e r p e n e t r a t i o n of t h e cell w h o s e discharge was s h o w n in F i g u r e C, a n d a f t e r d e t e r i o r a t i o n of t h e spike p o t e n t i a l , a depolarizing-hyperpolarizing potential sequence remains. T h e i n t r a c e l l u l a r r e c o r d i n g s h o w n in F i g u r e D is s h o w n a t t w o d i f f e r e n t gains a n d w i t h t w o d i f f e r e n t sweep speeds. T h e E P S P n a t u r e of t h e d e p o l a r i z i n g p o t e n t i a l is s h o w n in F i g u r e F. T h e b e h a v i o r of sucll d e p o l a r i z i n g p o t e n t i a l s was t h e n examined by systematically changing the stimulus i n t e n s i t y (Figure F). W i t h a s t i m u l u s i n t e n s i t y a 4.0 T (4 • t h r e s h o l d ) , a spike is issued. As t h e s t i m u l u s i n t e n s i t y is r e d u c e d t h e spike d i s a p p e a r s a n d t h e d e p o l a r i z i n g p o t e n t i a l s decrease in a m p l i t u d e . H o w e v e r , t h e r e is no Significant i n c r e a s e in t h e l a t e n c y to o n s e t (the a r r o w i n d i c a t e s t h e o n s e t a t 2.3 .T). T h e w a v e form, g r a d e d

]~XPERIENTIA31/7

n a t u r e , a n d lack of l a t e n c y s h i f t for t h e s e d e p o l a r i z i n g potentials indicate that they represent monosynaptic EPSPs. Some of t h e ceils w h i c h were o r t h r o d r o m i c a l l y a c t i v a t e d b y M F B i n p u t could be a n t i d r o m i c a l l y a c t i v a t e d b y I F i m s t i m u l a t i o n . A n e x a m p l e is s h o w n in F i g u r e H a n d I. F i g u r e I shows a u n i t a r y d i s c h a r g e r e c o r d e d f r o m t h e s a m e cell, w i t h a l a t e n c y of 2 msec following I F i m s t i m u l a t i o n . T h e a n t i d r o m i c n a t u r e of t h i s u n i t is e v i d e n c e d b y r e c o v e r y in a 3.0 msec I S I . T h e d a t a p r e s e n t e d here i n d i c a t e t h a t a t l e a s t some of t h e p r o j e c t i o n s c o u r s i n g v i a t h e M F B are e x c i t a t o r y w i t h r e s p e c t to t h e i r t a r g e t cells in t h e n D B B . This is in a g r e e m e n t w i t h o t h e r e l e c t r o p h y s i o l o g i c a l studies n,12 w h e r e M F B s t i m u l a t i o n leads t o t h e a p p e a r a n c e of e x t r a cellular u n i t a r y a c t i v i t y in t h e n D B B .

Summary. T h e e l e c t r o p h y s i o l o g i c a l c h a r a c t e r i s t i c s of t h e m e d i c a l f o r e b r a i n b u n d l e ( M F B ) p r o j e c t i o n s to t h e n u c l e u s of t h e d i a g o n a l b a n d of B r o c a ( n D B B ) were s t u d i e d in a c u t e l y p r e p a r e d cats. M F B s t i m u l a t i o n e v o k e d field p o t e n t i a l s w h i c h c o n s i s t e d of a large n e g a t i v e w a v e followed b y a shallow p o s i t i v i t y . E x t r a c e l l u l a r u n i t a r y discharges a p p e a r e d o u t of t h e n e g a t i v i t y . I n a d d i t i o n , intracellularly recorded EPSPs showed no significant s h i f t in t h e l a t e n c y to o n s e t w i t h c h a n g e s in s t i m u l u s int e n s i t y . T h e s e o b s e r v a t i o n s i n d i c a t e t h a t a t l e a s t some of t h e M F B p r o j e c t i o n s to t h e n D B B are e x c i t a t o r y w i t h respect t o t h e i r t a r g e t cells. J. F. DEFRANCE a n d H. Y O S H I H A R A TM 14

_~Iorin Memorial Laboratory, Department o/Anatomy, Wayne State University School o/Medicine, 550 East Can/ield A venue, Detroit (Michigan 48201, USA), 10 March 1975. 10 S. RAMO• y CAJAL,Studies on the Cerebral Cortex. Translated by KRAFT (The Year Book Publishers, Chicago 1955), p. 135. 11 H . EDINGER, A. SIEGEL a n d R. TROIANO, E x p l Neurol. $1, 569

(1973). 13 j. S. MeKENZlE and D. K. ROGERS, personal comnnmication (1974). 18 The authors appreciate the suggestions and critical review of the manuscript by Dr. S. T. KITAI. 14 This work was supported by NSF Grant No. GB 35532 and NIH Grants Nos. NS 00405 and RR 5384.

B l o o d P r e s s u r e R e g u l a t i o n in S p o n t a n e o u s l y H y p e r t e n s i v e Rats 1 Spontaneously hypertensive rats (SHR) from a Wistar s t r a i n 2, e x h i b i t a s u s t a i n e d increase in v a s c u l a r resistance, a t l e a s t w h e n t h e y are 18 weeks or older 3. Studies on S H R , as well as on h u m a n essential h y p e r t e n s i o n , suggest that an increased media thickness, partly encroaching u p o n t h e v a s c u l a r l u m e n of r e s i s t a n c e vessels, f o r m s t h e m a i n b a c k g r o u n d of t h e i n c r e a s e d flow r e s i s t a n c e 4, 5. I n c r e a s e d v a s c u l a r r e a c t i v i t y in SI-IR is also r e p o r t e d a n d a t t r i b u t e d to a n i n c r e a s e d ionic p e r m e a b i l i t y r e g u l a t ing s m o o t h m u s c l e tensionS-S. I n spite of t h e h i g h blood pressure, efficient b a r o r e f l e x r e g u l a t i o n occurs. W e describ e d some h i s t o l o g i c a l a s p e c t s of i n t i m a l a n d m e d i a l vasc u l a r h y p e r t r o p h y in t h e c a r o t i d arteries a n d aortic a r c h of o u r S H R colonyg. T h e p r e s e n t s t u d y p r o v i d e s m o r p h o m e t r i c d a t a on t h e m e d i a l v a s c u l a r h y p e r t r o p h y , w h i c h will d i m i n i s h t h e t r a n s m i s s i o n of t h e p r e s s u r e pulse signal to t h e b a r o receptors, l o c a t e d b e t w e e n t h e m e d i a a n d t h e a d v e n t i t i a 10

Material and methods. Male S H R were c o m p a r e d to n o r m o t e n s i v e W i s t a r r a t s ( N W R ) of o u r o w n p e r m a n e n t l a b o r a t o r y c o l o n y e s t a b l i s h e d in 1956. T h e a n i m a l s were transiently anaesthetized with ether and the femoral a r t e r y was c a t h e t e r i z e d u n d e r local a n a e s t h e s i a w i t h lidocaine. 1 h a f t e r r e c o v e r y f r o m t h e e t h e r a n a e s t h e s i a , h e a r t r a t e , systolic a n d diastolic b l o o d pressures were recorded. T h e r e a f t e r , t h e r a t s were a n a e s t h e t i z e d w i t h H y p n o r m | (haloanisone, 10 m g / k g a n d f e n t a n y l , 0,1 rag/ k g s.c.). U n d e r free v e n o u s outflow, t h e a r t e r i a l c i r c u l a t i o n was fixed r e t r o g r a d e l y in situ w i t h 2 % g l u t a r M d e h y d e in 0.1 M c a c o d y l a t e b u f f e r a t a s u s t a i n e d p e r f u s i o n pressure of 120 or 200 m m Hg. T h e i n t e r n a l c a r o t i d a r t e r y was t a k e n a t 2 m m f r o m its origin a n d t h e aortic a r c h a t 1 c m f r o m t h e h e a r t . T h e s a m p l e s were postfixed, e m b e d d e d , s t a i n e d a n d t r a n s v e r s e l y c u t as p r e v i o u s l y described 9. T h e p e r i m e t e r s of t h e i n n e r a n d o u t e r side of t h e m e d i a were m e a s u r e d w i t h a c u r v i m e t e r (precision = 1 m m ) o n

15. 7. 1975

811

Specialia

Matched pairs of normotensive (NWR) and hypertensive rats (SHR}.

Strain

NWR SHR NWR

SHR

NWR

Aortic arch

Left internal carotid artery

Right internal carotid artery

SBP (mmHg)

DBP (mmHg)

HR (beats/rain)

Ri WT WT (~zm) (~LIn) R~'-

Ri (~LIn)

WT

WT

Ri

(~LIn)

Ri

(~/.In)

3 3 3 3

145 160 280 240

100 110 170 165

440 390 420 410

-1165 1049 1185

-125 164 164

-0.107 0.157 0.139

327 301 337 363

32 33 50 45

0.098 0.110 0.148 0.121

331

7 7 7 7 7 7

130 150 90 225 200 240

90 95 55 160 150 155

390 420 390 470 390 370

1257 1410 1410 1059 1194 1143

110 121 131 143 173 165

0.087 0.086 0.093 0.135 0.145 0.144

336 426 375 352 425 387

36 38 51 65 60 69

0.107 0.091 0.137 0.183 0.142 0.178

12 12 12 12 12 12

150 125 135 150 155 155

95 85 85 100 95 85

420 360 450 420 440 420

1154 1216 -1704 1329 1124

125 105 -118 142 141

0.108 0.086 -0.069 0.107 0.125

326 364 350 391 467 359

35 46 37 41 46 39

0.109 0.126 0.106 0.104 0.098 0.108

Age (months)

median values:

]50 9

SHR

220 200 170 250 245 260

12 12 12 12 12 12

Medianvalues:

232 a

90~

WT (~Lnl)

Ri

40 -54 60

0.121 -0.160 0.208

375 334 375 471

35 51 46 65 71 62

0.108 0.118 0.123 0.148 0.189 0.131

368 372 327 382 373 384

42 35 50 46 43 44

0.115 0.095 0.092 0.120 0.114 0.115

333 289 327

427

WT

420

1216

125 9

0.107~

361 ~

40 ~

0.107 9

372 9

42 9

0.115~

145

390

150

400 420 350 400 400

195 151 177 223 188 199

0.153 0.114 0.158 0.168 0.144 0.166

582 482 407 495 482 460

68 62 66 73 69 65

0.117 0.129 0.164 0.150 0.143 0.140

413 361 . . 532 491 471

63 52 . . 71 64 67

0.156 0.143

95 185 175 180

1274 1330 1122 1384 1308 1200

0.134 0.132 0.142

162~

400

1291

191 9

0.155~

484 a

67 a

0.141 .

471~

64~

0.142~

Significant difference between NWR and SHR group (p ~-~ 0.05, Mann-Whitney-U-test); sample lacking for technical reasons. SBP, systolic blood pressure; DBP, diastolic blood pressure; Ri, inner radius; WT, wall thickness.

p h o t o g r a p h s of t h e a r t e r i a l c r o s s - s e c t i o n s . M a g n i f i c a t i o n s r a n g e d f r o m 25 t i m e s f o r a o r t i c a r c h e s u p t o 110 t i m e s f o r internal carotid arteries. The perimeter values were divided by 2 II and the difference between outer and i n n e r r a d i u s ( R o - R d w a s t a k e n a s a m e a s u r e m e n t of t h e medial wall thickness (WT). Results. R e s p e c t i v e l y , 2, 3 a n d 6 p a i r s of e x p e r i m e n t s w e r e c a r r i e d o u t w i t h S H R a n d N W R a t t h e a g e of 3, 7 a n d 12 m o n t h s . T h e r e s u l t s a r e s h o w n i n t h e T a b l e . I n b o t h t y p e s of a r t e r i e s a n d a t a l l a g e s , t h e m e d i a l w a l l w a s a p p r o x i m a t e l y 50~o t h i c k e r i n S H R t h a n i n N W R . I n a l l instances, evaluation in groups with 5 or more samples showed that this difference was highly significant. Since WT/R, is i n f l u e n c e d b y t h e p e r f u s i o n p r e s s u r e a t t h e m o m e n t of f i x a t i o n , m e a s u r e m e n t s w i t h d i f f e r e n t p e r fusion pressures were performed on internal carotid a r t e r i e s of 3 m o n t h o l d S H R . T h e m e d i a n v a l u e s of W T / R , w e r e 0.162 (n = 8) a t 120 m m H g a n d 0.149 (n ~ 6) a t 200 m m H g a n d t h i s d i f f e r e n c e w a s n o t s t a t i s t i c a l l y significant. Nevertheless, it must be kept in mind that the m o r p h o n l e t r i c d a t a of t h e T a b l e w e r e o b t a i n e d a t e q u a l intraluminal fixation pressures. Consequently, the reported difference between N'WR and SHR regarding WT and e s p e c i a l l y WT/R~ will be s l i g h t l y less i m p o r t a n t in t h e l i v i n g a n i m a l a t t h e p r e v a i l i n g b l o o d p r e s s u r e level. Of c o u r s e , t h e m e d i a l h y p e r t r o p h y i n S H R is n o t r e s t r i c t e d t o t h e l e v e l of t h e b a r o r e c e p t o r a r e a s b u t o c c u r s a l s o a t other sites, such as the common carotid arteries and the abdominal aortag. According to morphometrie data r e p o r t e d o n t h e a s c e n d i n g a o r t a of 5 t o 12 m o n t h o l d r a t s n , t h e m e d i a l a o r t i c w a l l t h i c k n e s s w a s 0.160 ~zm for N W R a n d 230 ~xm for S H R . I n o u r e x p e r i m e n t s w i t h 12-

m o n t h - o l d r a t s t h e m e d i a l t h i c k n e s s of t h e a o r t i c a r c h w a s 125 ~ m ( m e d i a n v a l u e ) for N W R a n d 191 tzm f o r S H R . W e a t t r i b u t e t h e d i f f e r e n c e of t h e a b s o l u t e v a l u e s mainly to the fact that our samples were fixed under a p e r f u s i o n p r e s s u r e of 120 m m H g , w h e r e a s YURUKOVA a n d KtPROV 11 u s e d i m m e r s i o n f i x a t i o n i n t h e a b s e n c e of any intraluminal pressure. Other published findings on t h e t h o r a c i c a o r t a r e p o r t e d a w a l l t h i c k n e s s of 80 t o 100

1 This study is pa rt l y supported by a grant from I. W. O. N. L., Belgium. 2 K. OKA~IOTO, in International Review o! Experimental Pathology (Eds. G, W. RICHTER and M. A. EPSTEIN; Academic Press, New York. 1969), vol. 7, p. 227. 3 M. A. PFEFFER and E. D. FR6HLICH, Circulation Res. Suppl. ,32 and 33, I 28 (1973). 4 B. FOLKOW, M. HALLBACK, Y. I,UNDGREN, 1~. SIVERTSSON and L. WEISS, in Spontaneous Hypertension its Pathogenesis and Complications (Ed. K. OKAMOTO; Igaku Shoin Ltd., Tokyo 1972), p. 103.

.5 M. HALLBACK, Y. LUNDGREN and L. WEISS, Acta physiol, scand. 90, 57 (1974). 6 A. W. JONES, Fed. Proc. 33, 133 (1974). : E. T. HOLLOWAYand D. F. BOHR, Circulation Res. 33, 678 (1973). s F. P. FIELD, R. A. JANIS and D. J. TRIGGLE, Can. J. Physiol. Pharmac. 50, 1072 (1972). 9 D. WELLENS, M. BORGERS and VERHEYEN A., Experientia 29, 1268 (1973). 10 A. ABRAHAM, in il~Iicroscopie Innervation o! the Heart and Blood Vessels in Vertebrates Including Man (Pergamon Press, London 1969). 11 g. B. YURUKOVA and D. I. KIPROV, Dokl. Bulg. Akad. Nauk. 26 113 (1973).

812

Specialia

F m for 16- t o 28-week-old n o r m o t e n s i v e r a t s a n d of 120 to 140 F m w h e n t h e a n i m a l s were m a d e h y p e r t e n s i v e l e : I n t h i s l a t t e r s t u d y , f i x a t i o n of t h e arteries was p e r f o r m e d in v i t r o a t v a r y i n g pressures a c c o r d i n g to t h e blood p r e s s u r e level. W e a s s u m e t h a t t h e e x t e n s i v e m a n i p u l a t i o n of t h e a r t e r i e s in v i t r o a n d in t h e a b s e n c e of f u n c t i o n a l s y m p a t h e t i c i n n e r v a t i o n h a s led t o u n p h y s i o l o g i c a l d i l a t a t i o n . I n o u r e x p e r i m e n t s , t h e systolic a n d diastolic blood pressures of S H R were m u c h h i g h e r t h a n t h o s e of N W R , w h e r e a s t h e h e a r t r a t e v a l u e s were n o t different. T h i s was a general f e a t u r e o b s e r v e d in o u r S H R colony. Discussion. O u r f i n d i n g s suggest t h e following i n t e r p r e t a t i o n of b l o o d p r e s s u r e r e g u l a t i o n in S H R . T h e b a r o r e c e p t o r n e r v e - e n d i n g s of S H R are p r o t e c t e d a g a i n s t excessive s t i m u l a t i o n in spite of t h e h y p e r t e n s i o n , since t h e t r a n s m i s s i o n of t h e p r e s s u r e signal t h r o u g h t h e m e d i a l s m o o t h muscles is d a m p e n e d to a larger e x t e n t as in N W R . T h i s e x p l a i n s w h y t h e e f f e r e n t s y m p a t h e t i c t o n e is n o t d e p r e s s e d a t t h e level of t h e v a s o m o t o r c e n t e r a n d w h y t h e h e a r t r a t e is n o t slowed d o w n in t h e h y p e r t e n s i v e rats. On t h e c o n t r a r y , some a v a i l a b l e d a t a i n d i c a t e t h a t e f f e r e n t s y m p a t h e t i c d i s c h a r g e r a t e is r a t h e r increased in S H R , as c o m p a r e d t o n o r m o t e n s i v e la,14 or r e n a l h y p e r t e n s i v e rats15. I n p a r t i c u l a r , o u r f i n d i n g s e x p l a i n a n im-

220200~ " ' ~ ' ~ % ' ,

Dampening of "~,baroieceptor input

~\\

180

, "~ 14C ~ 12c

? 100 ~ m

ctivi,y

~Increasedperipheral

.

N

40 6'0

S HR

O 80

R 160 189 140 160 180 200 220 2z10

Carotid sinusperfusion pressure(ramHg) O--O, experimental values published by NOSAKA and WANG17. 9 -- 9 theoretical curve of NCR with increased peripheral reactivity, whithout modification of the baroreeeptor setpoint.

EXPERIENTIA 31/7

p o r t a n t a s p e c t of t h e m o d i f i e d b a r o r e c e p t o r f u n c t i o n s r e p o r t e d in S H R 16, 17. NOSAKA a n d WANG 17h a v e t a b u l a t e d their measurements, describing the relationship between s y s t e m i c a r t e r i a l p r e s s u r e a n d c a r o t i d sinus p e r f u s i o n pressure. W e h a v e r e p r e s e n t e d t h e i r results in a d i a g r a m (Figure) a n d we h a v e d r a w n t h e t h e o r e t i c a l curve, w h i c h w o u l d b e o b t a i n e d if S H R h a d o n l y a g r e a t e r 'effector r e s p o n s e ' in c o m p a r i s o n w i t h N W R . T h e s e factors, w h e t h e r t h e y r e s u l t f r o m a g r e a t e r a m o u n t 4,5 or f r o m a n i n c r e a s e d r e a c t i v i t y ",7 of t h e v a s c u l a r s m o o t h m u s c l e cells in t h e r e s i s t a n c e vessels, w o u l d o n l y elicit a n u p w a r d s h i f t of t h e r e l a t i o n s h i p - c u r v e . I t is clear t h a t t h e r e s u l t s of NOSAKA a n d W A N t w i t h S H R also r e v e a l a n i m p o r t a n t s h i f t of t h e c u r v e f r o m left t o right, s h o w i n g t h a t a g r e a t e r c a r o t i d sinus p r e s s u r e is n e c e s s a r y before b a r o r e c e p t o r r e g u l a t o r y f u n c t i o n comes i n t o play. T h e s e a u t h o r s s p e c u l a t e u p o n a n increased r i g i d i t y of t h e sinus wall. O u r m o r p h o m e t r i c s t u d i e s on t h e m e d i a l h y p e r t r o p h y in v a s c u l a r s t r e t c h - r e c e p t o r areas of S H R p r o v i d e d i r e c t e v i d e n c e for a s t r u c t u r a l basis of t h i s h o r i z o n t a l s h i f t of b a r o r e c e p t o r f u n c t i o n due to d a m p e n i n g of t h e i n p u t signal.

Zusammen/assung. M o r p h o m e t r i s c h e D a t e n bei R a t t e n m i t g e n e t i s c h e m H o c h d r u c k zeigen, dass die M e d i a d e r Gef/isswand u m e t w a 5 0 % dicker ist als bei n o r m o t o n e n Tieren. Diese V e r d i c k u n g e n sind i m A o r t e n b o g e n u n d in der N~Lhe des K a r o t i s s i n u s g e m e s s e n worden, wo Pressorr e z e p t o r e n a n der A u s s e n s e i t e der M e d i a liegen. Die herv o r g e r u f e n e V e r s c h i e b u n g der P r e s s o r r e z e p t o r - S t e u e r u n g wird i m Z u s a m m e n h a n g m i t der v e r & n d e r t e n B l u t d r u c k r e g u l i e r u n g bei g e n e t i s c h h y p e r t o n e n R a t t e n d i s k u t i e r t .

I). WELLENS, A. VERHEYEN and M. BORGERS Janssen Pharmaceutica, Departments o/ Cardiovascular Research and Cell Biology, Koninklijke Laan 77, B-23dO Beerse (Belgium), 11 September 7974. 12 H. WOLINSKY,Circulation Res. 26, 507 (1970). 13 j. IRIUCHIJIMA,Jap. Heart J. 7d, 350 (1973). 14 A. NAGAOKA, I(. KIKUGItI and Y. ARAMAKI,Jap. J. Pharmae. 19,

401 (1969). 15 A. EBIHARA and B. L. MARTZ, Am. J. reed. Sci. 259, 257 (1970). 16 S. NOSAKA and K. OKAMOTO, Jap. Circulation J. 34, 685 (1970). 17 S. NOSAKA and S. C. WANG, Am. J. Physiol. 222, 1079 (1972).

B i l a t e r a l R e s e c t i o n of S u p e r f i c i a l R a t K i d n e y C o r t e x : Effect o n S o d i u m B a l a n c e F u n c t i o n a l h e t e r o g e n e i t y of t h e n e p h r o n p o p u l a t i o n h a s b e e n p o s t u l a t e d since some y e a r s 1. T h e r e was no e x p e r i m e n t a l model, h o w e v e r , for d i r e c t studies on j u x t a m e d u l l a r y n e p h r o n s in conscious a n i m a l s . RASHID et al. 2 r e c e n t l y d e v e l o p e d s u c h a n e x p e r i m e n t a l ' model, prod u c i n g u n i l a t e r a l necrosis of t h e o u t e r r a b b i t k i d n e y c o r t e x b y surface h y p e r t h e r m i a . W e p r e s e n t here a s i m i l a r m o d e l : b i l a t e r a l surgical a b l a t i o n of t h e whole superficial k i d n e y cortex. S o d i u m b a l a n c e was s t u d i e d in r a t s s u b j e c t e d to t h i s t y p e of p a r t i a l n e p h r e c t o m y . Material and methods. Male W i s t a r r a t s w e i g h i n g 3 5 0 450 g were used. Operative procedures. All r a t s were a n e s t h e t i z e d w i t h ether. B o t h k i d n e y s were exposed f r o m dorsal a n d t h e r e n a l pedicles were c l a m p e d for a few m i n u t e s . T h e r a t s were t h e n d i v i d e d i n t o 4 g r o u p s a n d e a c h g r o u p was t r e a t ed in a d i f f e r e n t way. G r o u p I : no f u r t h e r t r e a t m e n t

( s h a m o p e r a t i o n ) . G r o u p I I : n e p h r e c t o m y on t h e r i g h t side. G r o u p I I I : n e p h r e c t o m y on t h e r i g h t side + pole r e s e c t i o n on t h e left k i d n e y ~ a p p r o x i m a t e l y 4/6 n e p h r e c t o m y ~. G r o u p I V : r e s e c t i o n of t h e whole o u t e r k i d n e y c o r t e x u s i n g a s h a r p scissor. Thus, a b o u t 50% of k i d n e y tissue was r e m o v e d . T h e w o u n d surfaces were t h o r o u g h l y dried w i t h filter paper, a n d t h e n covered w i t h H i s t o a c r y l | B r a u n , Melsungen. Seconds l a t e r t h e r e n a l pedicle c l a m p was r e m o v e d . G e n e r a l l y no b l e e d i n g occurred.

1 M. HORSTERand K. TtIURAU, Pflfigers Arch. ges. Physiol. 301, 162 (1968). 2 H. A. RASHID, C. A. LINKE, T. BOI~GIGLIOand M. S. Wu, J. appl. Physiol. 37, 228 (1974). 3 p. p. FIGDOR, Urol. int. 23, 388 (1968).