Feeding-related hypothalamic neurons modulate the H1-receptor to control feeding behavior in rats

S67 DIFFERENTIAL

CHARACTERISTICS

OF L H A - N E U R O N S

Z O L T A N KARADI*, Y U T A K A O O M U R A A N D H I T O O l o g i c a l Sciences, O k a z a k i 444, J a p a n

IN THE A W A K E

NISHINO,

MONKEY

National

Institute

for P h y s i o -

The lateral h y p o t h a l a m i c area (LHA) is i n t i m a t e l y i n v o l v e d in the r e g u l a t i o n of f e e d i n g behavior, in p r o c e s s i n g v a r i o u s " e x t r i n s i c " and " i n t r i n s i c " s i g n a l s as w e l l as in l e a r n i n g a n d m e m o r y m e c h a n i s m s . Despite extensive research, the f u n c t i o n a l o r g a n i z a t i o n of L H A - n e u r o n s is not yet w e l l defined. To f a c i l i t a t e a b e t t e r u n d e r s t a n d i n g of t h e s e neurons, t h e i r i n p u t - o u t p u t o r g a n i z a t i o n as w e l l as t h e i r a c t i v i t y changes during gustatory and olfactory stimulations were studied. E l e c t r i c a l s t i m u l a t i o n of the o r b i t o f r o n t a l c o r t e x e v o k e d f i r i n g rate c h a n g e s in m o r e g l u c o s e - s e n s i t i v e (GS) than g l u c o s e - i n s e n s i t i v e (GIS) neurons. In contrast, G I S - n e u r o n s r e s p o n d e d m o r e o f t e n to m o t o r c o r t e x s t i m u l a t i o n than did GS-neurons. Olfactory stimuli elicited numerous responses in t h e v a s t m a j o r i t y of the G S - n e u r o n s , w h e r e a s f e w e r than 50% of the G I S - n e u r o n s r e s p o n d e d to smells. G u s t a t o r y s t i m u l a t i o n s r e s u l t e d in d i s c h a r g e c h a n g e s in over 2/3 of the GS-neurons, while o n l y I/3 of t h e G I S - n e u r o n s reacted thusly. Taster e s p o n d i n g G S - n e u r o n s , u n l i k e t h o s e of G I S - n e u r o n s , o f t e n e x h i b i t e d f i r i n g rate c h a n g e s in r e s p o n s e to t w o or m o r e t a s t e q u a l i t i e s or o d o r a n t s . O u r r e s u l t s s u g g e s t that GS- and G I S - n e u r o n s of the LHA have d i f f e r e n t f u n c t i o n a l o r g a n i z a tions for i n t e g r a t i n g d i f f e r n t t y p e s of c h e m i c a l ( m e t a b o l i t e s , tastes, etc.) and o t h e r i n f o r m a t i o n w h i c h are d e c i s i v e l y i m p o r t a n t in the r e q u l a t i o n of feeding.

FEEDING_RELATED~CNEURONSMOIXJLATETHEH1-RECEPTORTOCOMTROLFEEDII~BEHAVIOR IN BATS. SHIRAISHI I , KOJI TAKEMASA Dept. of Physiol., Tokai

FUKAGAWA 2, HIRONOBU YOSHIMATSU 2, KAZUMA ~UJIMOTO 2 and TOSHIIE SAKATA 2 Univ. Sch. of Med., Isehara 259-11 and ADept. Internal Med., Fac. of Med., Kyushu Univ. 71, Fukuoka 812, Japan It has been reported that the histamine HI but not the H2-receptor antagonist markedly induced feeding dose-dependently after intra-third Eerebroventricular (i.c.v.) infusion in the early light (ll:OO h), when hypothalamic histamine content was highest. Feeding elicitatlon was attenuated after i.c.v, infusion in the early dark (19:40 h), when the histamine level was low, and was abolished after intraperitoneal (i.p.) pretreatment with~-fluromethylhistidine (a-FMH), a specific inhibitor of the neuronal histamine synthetic enzyme, histidine decarboxylase. The present study was undertaken to investigate the involvement of feeding-related ventromedial hypothalamic (VMB) and lateral hypothalamic (LHA) neurons of Wistar SPF male rats under acute conditions. Anesthesia, a mixture of urethane (500 mg/kg) and ~ -chloralose (30 mg/kg), was administered intramuscularly. In the LHA in 43 rats, electrophoretic application of the H lantagonist, chlorpheniramine (CPR), facilitated neuronal activity of 43 (47.8%) of 90 glucosesensitive neurons, but had no significant effect on non-glucose sensitive neurons. In contrast, in the VMH (n=lS), CPR significantly inhibited (24/30, 80%, p