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Inputs from the lateral vestibular nucleus to the lateral hypothalamic area in rats
$43
7 Hypothalamus INPUTS RATS
FROM
THE
LATERAL
VESTIBULAR
NUCLEUS
TO
THE
LATERAL
HYPOTHALAMIC
AREA
TOSHIHIKO KATAFUCHI , HIRONOBU YOSHIMATSU , KUKKADI PADMANABHA PUTHURAYA , Y U T A K A O O M U R A . D e p a r t m e n t of P h y s i o l o g y , F a c u l t y of M e d i c i n e , K y u s h u U n i v e r s i t y F u k u o k a 812, J a p a n
IN
and 60,
The recent development of gravitational physiology has revealed that vestibulo-autonomic d i s o r d e r s s i m i l a r to m o t i o n s i c k n e s s h a v e b e e n o b s e r v e d d u r i n g space flight. Since the h y p o t h a l a m u s is i m p l i c a t e d in the r e g u l a t i o n of the autonomic nervous system, it is p o s s i b l e t h a t the h y p o t h a l a m u s has an i m p o r t a n t relationship to v e s t i b u l o - a u t o n o m i c disorders in w e i g h t l e s s n e s s . In the p r e s e n t study, to c l a r i f y v e s t i b u l a r i n p u t s to the l a t e r a l h y p o t h a l a m i c a r e a (LHA) f r o m the lateral vestibular nucleus (LVN), the e f f e c t s of LVN stimulation on n e u r o n a l activity in the rat LHA, including specific glucose-sensitive neurons, were i n v e s t i g a t e d by e x t r a c u l l u l a r and intracellular r e c o r d i n g s in vivo. The a n i m a l w a s anesthetized with a mixture of u r e t h a n e and ~-choloralose. Stimulation of the contralateral L V N e v o k e d t h r e e t y p e s of r e s p o n s e in 46 % (111/240) of the n e u r o n s recorded extracellularly: long l a t e n c y ( 3 8 . 1 ± 2 3 . 6 msee) e x c i t a t i o n (62/111, 56 %), short latency (6.9±3.1 msec) e x c i t a t i o n - i n h i b i t i o n (33/111, 30 %), a n d i n h i b i t i o n with 20.1±11.1 msec latency (16/111, 14 %). Glucose-sensitive neurons, which were identified by an electrophoretic application technique, did not respond specifically to such s t i m u l a t i o n . Neuronal activity was recorded intracellularly f r o m 31 L H A n e u r o n s , of w h i c h 13 r e s p o n d e d to L V N s t i m u l a t i o n . S e v e n of the 13 neurons s h o w e d a long l a t e n c y E P S P and the r e m a i n i n g 6 exhibited an E P S P - I P S P s e q u e n c e w i t h a s h o r t e r latency. T h e a m p l i t u d e of t h e s e r e s p o n s e s w a s g r a d e d 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 . The E P S P s of b o t h t y p e s of r e s p o n s e w e r e c o n s i d e r e d to be p o l y s y n a p t i c because of the shortening of latencies by h i g h e r current stimulation. S i n c e the L B A is i m p l i c a t e d in the r e g u l a t i o n of the a u t o n o m i c n e r v e a c t i v i t y , the p r e s e n t r e s u l t s s h o w i n g p o l y s y n a p t i c p a t h w a y s from the L V N to the L H A s u g g e s t the f u n c t i o n a l i n v o l v e m e n t of the L H A in v e s t i b u l o - a u t o n o m i c responses.
DIFFERENT PATHS ARE TAKEN BY MIDBRAIN NEURONS WITH DIFFERENT CELL SIZES YASUO SAKUMA and TAKAO AKAISHI ~, Medicine, Niigata 951, Japan
PROJECTIONS OF TWO CLASSES OF VENTROMEDIAL HYPOTHALAMIC
Department
of
Physiology
II,
Niigata University School of
Antidromic action potentials were recorded in and around the region of the ventromedial nucleus of the hypothalamus (VMN) of urethane-anesthetized ovariectomized female rats following stimulation of the mesencephalic central gray (CG). The animals had either the lateral or caudal trajectory of the VMN efferent to the CG disrupted acutely by a small knife-cut. Changes in the shape of the antidromic action potentials were recorded for each response as the recording electrode was advanced at lO um intervals from the point of detection of the potential until its deterioration. The antidromic potentials had positive-negative configuratfon throughout the entire extracellular field, suggesting their generation by neuronal soma with simple geometries. The spatial spread of the extracellular antidromic action potentials was represented by the distance travelled by the recording electrode, at which peak-to-peak spike amplitude exceeded the half maximum value. The frequency distribution of the spatial spread was nearly unimodal for 36 responses (range: 42-183 ~m) in 16 animals bearing the posterior knife-cut, and also for 26 responses (range: 32-165 ~m) in 15 animals with the lateral cut. Mean spatial spread (P
7 Hypothalamus INPUTS RATS
FROM
THE
LATERAL
VESTIBULAR
NUCLEUS
TO
THE
LATERAL
HYPOTHALAMIC
AREA
TOSHIHIKO KATAFUCHI , HIRONOBU YOSHIMATSU , KUKKADI PADMANABHA PUTHURAYA , Y U T A K A O O M U R A . D e p a r t m e n t of P h y s i o l o g y , F a c u l t y of M e d i c i n e , K y u s h u U n i v e r s i t y F u k u o k a 812, J a p a n
IN
and 60,
The recent development of gravitational physiology has revealed that vestibulo-autonomic d i s o r d e r s s i m i l a r to m o t i o n s i c k n e s s h a v e b e e n o b s e r v e d d u r i n g space flight. Since the h y p o t h a l a m u s is i m p l i c a t e d in the r e g u l a t i o n of the autonomic nervous system, it is p o s s i b l e t h a t the h y p o t h a l a m u s has an i m p o r t a n t relationship to v e s t i b u l o - a u t o n o m i c disorders in w e i g h t l e s s n e s s . In the p r e s e n t study, to c l a r i f y v e s t i b u l a r i n p u t s to the l a t e r a l h y p o t h a l a m i c a r e a (LHA) f r o m the lateral vestibular nucleus (LVN), the e f f e c t s of LVN stimulation on n e u r o n a l activity in the rat LHA, including specific glucose-sensitive neurons, were i n v e s t i g a t e d by e x t r a c u l l u l a r and intracellular r e c o r d i n g s in vivo. The a n i m a l w a s anesthetized with a mixture of u r e t h a n e and ~-choloralose. Stimulation of the contralateral L V N e v o k e d t h r e e t y p e s of r e s p o n s e in 46 % (111/240) of the n e u r o n s recorded extracellularly: long l a t e n c y ( 3 8 . 1 ± 2 3 . 6 msee) e x c i t a t i o n (62/111, 56 %), short latency (6.9±3.1 msec) e x c i t a t i o n - i n h i b i t i o n (33/111, 30 %), a n d i n h i b i t i o n with 20.1±11.1 msec latency (16/111, 14 %). Glucose-sensitive neurons, which were identified by an electrophoretic application technique, did not respond specifically to such s t i m u l a t i o n . Neuronal activity was recorded intracellularly f r o m 31 L H A n e u r o n s , of w h i c h 13 r e s p o n d e d to L V N s t i m u l a t i o n . S e v e n of the 13 neurons s h o w e d a long l a t e n c y E P S P and the r e m a i n i n g 6 exhibited an E P S P - I P S P s e q u e n c e w i t h a s h o r t e r latency. T h e a m p l i t u d e of t h e s e r e s p o n s e s w a s g r a d e d 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 . The E P S P s of b o t h t y p e s of r e s p o n s e w e r e c o n s i d e r e d to be p o l y s y n a p t i c because of the shortening of latencies by h i g h e r current stimulation. S i n c e the L B A is i m p l i c a t e d in the r e g u l a t i o n of the a u t o n o m i c n e r v e a c t i v i t y , the p r e s e n t r e s u l t s s h o w i n g p o l y s y n a p t i c p a t h w a y s from the L V N to the L H A s u g g e s t the f u n c t i o n a l i n v o l v e m e n t of the L H A in v e s t i b u l o - a u t o n o m i c responses.
DIFFERENT PATHS ARE TAKEN BY MIDBRAIN NEURONS WITH DIFFERENT CELL SIZES YASUO SAKUMA and TAKAO AKAISHI ~, Medicine, Niigata 951, Japan
PROJECTIONS OF TWO CLASSES OF VENTROMEDIAL HYPOTHALAMIC
Department
of
Physiology
II,
Niigata University School of
Antidromic action potentials were recorded in and around the region of the ventromedial nucleus of the hypothalamus (VMN) of urethane-anesthetized ovariectomized female rats following stimulation of the mesencephalic central gray (CG). The animals had either the lateral or caudal trajectory of the VMN efferent to the CG disrupted acutely by a small knife-cut. Changes in the shape of the antidromic action potentials were recorded for each response as the recording electrode was advanced at lO um intervals from the point of detection of the potential until its deterioration. The antidromic potentials had positive-negative configuratfon throughout the entire extracellular field, suggesting their generation by neuronal soma with simple geometries. The spatial spread of the extracellular antidromic action potentials was represented by the distance travelled by the recording electrode, at which peak-to-peak spike amplitude exceeded the half maximum value. The frequency distribution of the spatial spread was nearly unimodal for 36 responses (range: 42-183 ~m) in 16 animals bearing the posterior knife-cut, and also for 26 responses (range: 32-165 ~m) in 15 animals with the lateral cut. Mean spatial spread (P