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A possible role of the trigeminal nerve in rabbit vestibular nystagmus
$178 A POSSIBLE
ROLE
OF THE
TRIGEMINAL
NERVE
IN R A B B I T
VESTIBULAR
NYSTAGMUS
S A T O S H I KASHII*, Y O S H I E M A T S U I I, Y O S H I H I T O H O N D A I, J U I C H I ITO 2, M A S A S H I S A S A a~d SHUJI TAKAORI, Department of P h a r m a c o l o g y , O p h t h a l m o l o g y I and O t o l a r y n g o l o g y ~, F a c u l t y of M e d i c i n e , K y o t o U n i v e r s i t y , K y o t o 606 S t u d i e s w e r e p e r f o r m e d to e l u c i d a t e the role of e x t r a o c u l a r p r o p r i o c e p t i o n in the v e s t i b u l o - o c u l a r r e f l e x u s i n g p i g m e n t e d rabbits. In the first e x p e r i m e n t , w h e n the location of t h e a f f e r e n t and efferent neurons to t h e e x t r a o c u l a r muscles was i n v e s t i g a t e d u s i n g r e t r o g r a d e t r a n s p o r t of h o r s e r a d i s h p e r o x i d a s e , the e x i s t e n c e of f i b e r c o n n e c t i o n s from the ophthalmic b r a n c h of t h e i p s i l a t e r a l trigeminal n e r v e (OB) w a s a l s o c o n f i r m e d in t h e r a b b i t . T h e n to e x a m i n e t h e e f f e c t s of t h e proprioception on t h e r o t a t i o n - i n d u c e d vestibular nystagmus(VN), t h e OB w a s t r a n s e c t e d at its j u n c t i o n w i t h the t r i g e m i n a l g a n g l i o n l o c a t e d at the base of the c r a n i u m . A s h a m o p e r a t i o n w a s p e r f o r m e d in a s i m i l a r m a n n e r , e x c e p t for t r a n s e c t i o n of the OB. In a dark, s o u n d - p r o o f room, the a n i m a l w a s p l a c e d on a t u r n t a b l e , that w a s r o t a t e d c l o c k w i s e or c o u n t e r c l o c k w i s e in the h o r i z o n t a l p l a n e at c o n s t a n t a n g u l a r v e l o c i t i e s of 30, 60, 90 and 1 2 0 ° / s for 45 s. Eye m o v e m e n t s w e r e r e c o r d e d using a nystagmograph 5 times before the operation and 5 times a week after recovery from surgery. There were no s i g n i f i c a n t changes in t h e n u m b e r or direction of t h e VN b e t w e e n t h e e y e w i t h t h e OB t r a n s e c t e d and that without t r a n s e c t i o n . W h e n the t u r n t a b l e was r o t a t e d at 30°/s, the eye on the o p e r a t e d side deviated in t h e d i r e c t i o n of t h e h e a d r o t a t i o n during the rotation a n d in t h e o p p o s i t e d i r e c t i o n i m m e d i a t e l y a f t e r the c e s s a t i o n of the r o t a t i o n , w h i l e the eye on t h e u n o p e r a t e d side remained approximately at t h e s a m e p o s i t i o n . When the r o t a t i o n w a s d o n e at a h i g h e r s p e e d of 90°/s, the eye on the o p e r a t e d side s h o w e d m o r e p r o n o u n c e d d e v i a t i o n in the d i r e c t i o n of the h e a d m o v e m e n t d u r i n g r o t a t i o n and in the o p p o s i t e d i r e c t i o n a f t e r the r o t a t i o n t h a n that on the u n o p e r a t e d side. T h e s e r e s u l t s s u g g e s t that e x r a o c u l a r p r o p r i o c e p t i o n p l a y s an i m p o r t a n t r o l e in c e n t e r i n g the eye in the orbit.
ROLE
OF THE
TRIGEMINAL
NERVE
IN R A B B I T
VESTIBULAR
NYSTAGMUS
S A T O S H I KASHII*, Y O S H I E M A T S U I I, Y O S H I H I T O H O N D A I, J U I C H I ITO 2, M A S A S H I S A S A a~d SHUJI TAKAORI, Department of P h a r m a c o l o g y , O p h t h a l m o l o g y I and O t o l a r y n g o l o g y ~, F a c u l t y of M e d i c i n e , K y o t o U n i v e r s i t y , K y o t o 606 S t u d i e s w e r e p e r f o r m e d to e l u c i d a t e the role of e x t r a o c u l a r p r o p r i o c e p t i o n in the v e s t i b u l o - o c u l a r r e f l e x u s i n g p i g m e n t e d rabbits. In the first e x p e r i m e n t , w h e n the location of t h e a f f e r e n t and efferent neurons to t h e e x t r a o c u l a r muscles was i n v e s t i g a t e d u s i n g r e t r o g r a d e t r a n s p o r t of h o r s e r a d i s h p e r o x i d a s e , the e x i s t e n c e of f i b e r c o n n e c t i o n s from the ophthalmic b r a n c h of t h e i p s i l a t e r a l trigeminal n e r v e (OB) w a s a l s o c o n f i r m e d in t h e r a b b i t . T h e n to e x a m i n e t h e e f f e c t s of t h e proprioception on t h e r o t a t i o n - i n d u c e d vestibular nystagmus(VN), t h e OB w a s t r a n s e c t e d at its j u n c t i o n w i t h the t r i g e m i n a l g a n g l i o n l o c a t e d at the base of the c r a n i u m . A s h a m o p e r a t i o n w a s p e r f o r m e d in a s i m i l a r m a n n e r , e x c e p t for t r a n s e c t i o n of the OB. In a dark, s o u n d - p r o o f room, the a n i m a l w a s p l a c e d on a t u r n t a b l e , that w a s r o t a t e d c l o c k w i s e or c o u n t e r c l o c k w i s e in the h o r i z o n t a l p l a n e at c o n s t a n t a n g u l a r v e l o c i t i e s of 30, 60, 90 and 1 2 0 ° / s for 45 s. Eye m o v e m e n t s w e r e r e c o r d e d using a nystagmograph 5 times before the operation and 5 times a week after recovery from surgery. There were no s i g n i f i c a n t changes in t h e n u m b e r or direction of t h e VN b e t w e e n t h e e y e w i t h t h e OB t r a n s e c t e d and that without t r a n s e c t i o n . W h e n the t u r n t a b l e was r o t a t e d at 30°/s, the eye on the o p e r a t e d side deviated in t h e d i r e c t i o n of t h e h e a d r o t a t i o n during the rotation a n d in t h e o p p o s i t e d i r e c t i o n i m m e d i a t e l y a f t e r the c e s s a t i o n of the r o t a t i o n , w h i l e the eye on t h e u n o p e r a t e d side remained approximately at t h e s a m e p o s i t i o n . When the r o t a t i o n w a s d o n e at a h i g h e r s p e e d of 90°/s, the eye on the o p e r a t e d side s h o w e d m o r e p r o n o u n c e d d e v i a t i o n in the d i r e c t i o n of the h e a d m o v e m e n t d u r i n g r o t a t i o n and in the o p p o s i t e d i r e c t i o n a f t e r the r o t a t i o n t h a n that on the u n o p e r a t e d side. T h e s e r e s u l t s s u g g e s t that e x r a o c u l a r p r o p r i o c e p t i o n p l a y s an i m p o r t a n t r o l e in c e n t e r i n g the eye in the orbit.