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Effect of VIP on SRIF release from rat hypothalamus: Differential responses of fetal and adult tissue
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E F F E C T OF V I P O N SRIF R E L E A S E F R O M RAT H Y P O T H A L A M U S : D I F F E R E N T I A L R E S P O N S E S OF FETAL AND ADULT TISSUE L. T a ~ i a - A r a n c i b i a , J. E~elbaum, A. Szafarcz~k,S. A r a n c i b L ~ G. Alonso, H. A s t i e r Lab of N e u r o e n d o c r i n o l o g y C, U A 639 CNRS F. 34060 Montpellier and Lab of N e u r o e n d o c r i n o l o g y , U 159 INSERM F. 75014 Paris. We h a v e p r e v i o u s l y r e p o r t e d that V I P i n h i b i t s the release of SRIF from slices of m e d i o b a s a l h y p o t h a l a m u s (MBH) in a d u l t rats (Epelbaum et al., Eur. J. Pharmacol, 5_88, 493, 1979). In contrast, V I P s t i m u l a t e s SRIF r e l e a s e from d i s p e r s e d d i e n c e p h a lic cells in c u l t u r e (Tapia-Arancibia and Reichlin, B r a i n Res, in press). To inv e s t i g a t e if p e r i n a t a l changes in the SRIF r e s p o n s e to VIP could e x p l a i n these o p p o s i t e e f f e c t s , t w o a p p r o a c h e s w e r e p e r f o r m e d : a/ in v i t r o : b y i n c u b a t i o n of MBH slices of fetal rats (day-3) and of n e o n a t a l rats (day 4 and day 15). The tissues w e r e i n c u b a t e d in L o c k e m e d i u m for Io min (with or w i t h o u t VIP), after a 40 m i n p r e i n c u b a t i o n period. SRIF was m e a s u r e d by RIA. b / in v i v o in c o n s c i o u s a d u l t rats, b y p e r f u s i o n of the m e d i a n e m i n e n c e (ME) u s i n g a p u s h - p u l l c a n n u l a in c o m b i n a t i o n w i t h a c a n n u l a i m p l a n t e d into the lateral v e n t r i c l e for V I P or saline injections. The ME was p e r f u s e d (20 ~i/min) w i ~ a r t i f i c i a l CSF and SRIF o ~ t p u t 6 m e a s u r e d in samples c o l l e c t e d e v e r y 15 min. R e s u l t s : in vitro, V I P (10 - 8 a n d 1 0 - M) s i g n i f i c a n t l y i n c r e a s e d SRIF release from fetal MEH. Data e x p r e s s e d as SRIF released in the m e d i u m in p e r c e n t of SRIF tissue c o n t e n t were: 2.39+0.72 and 3.34+1.O2 respectively, vs 1.22+O.35 in controls. In contrast, VIP did not stimulate SRIF r e l e a s e in n e o n a t a l rats: 0 . 3 0 + 0 . 0 7 and 0 . 8 2 + 0 . 4 0 vs 1.23+O.38 (day 4);O.54+O.21 and 1.O4+O.14 vs O . 9 3 + 0 . 1 4 (day 15).In vivo, IVT i n j e c t i o n of VIP (10 ~g/iO-~l) s t r o n g l y i n h i b i t e d SR~F o u t p u t from the ME w i t h i n 15 min, c o n f i r m i n g our p r e v i o u s in v i t r o data. C o n t r o l rats (10 ~i saline) e x h i b i t e d a normal p a t t e r n of p u l s a t i l e SRIF release. In addition, b y i m m u n o c y t o c h e m [ s t r y , we have o b s e r v e d n u m e r o u s VIPaxonal s y n a p t i c junctions on d e n d r i t e s in the p e r i v e n t r i c u l a r nucleus. Our d a t a s u g g e s t that rIP is a s t i m u l a t o r y factor of SRIF release d u r i n g the p r e n a t a l per i o d , d e v e l o p i n g later into an i n h i b i t o r y one. T h e s e findings indicate that VIP effects d e p e n d o n the m a t u r i t y of the h y p o t h a l a m u s .
SOMATOSTATIN EMHANCES THE INHIBITORY EFFECT OF GLUCAGON-37/O~DULIN (O X M ) A N D O F ITS C - T E R M I N A L O C T A P E P T I D E O N A C I D SECRETION. M. Dubrasquet~, M.-P. A u d o u s s e t - P u e c h z , J. MartinezZ, D. B a % a i l l e a I I N S E R M U.IO, PARIS, & a C e n t r e d e P h a r m a c o l o g i e - E n d o c r i n o l o g i e , MO~,'v~..T.IER, France. I n the a n e s t h e t i z e d rat, O X M is a p o t e n t a n d e f f i c i e n t i n h i b i t o r o f g a s t r i c a c i d s e c r e t i o n s t i m u l a t e d b y P e n t a g a s t r i n (P g ) I the C-terntinal octal)el)tlde o f O X M (K A S ) i n h i b i t s t h l s s t i m u l a t e d g a s t r i c secretion. In the s a m e model, e v i d e n c e w a s p r o d u c e d that S o m a t o s t a t i n (SM) i n h i b i t s g a s t r i n s t i m u l a t e d a c i d secretion. O u r p u r p o s e w a s to i n v e s t i g a t e the e f f e c t o f a s s o c i a t i o n s O X M + ~ 4 and K A 8 + S M o n the s t i m u l a t e d a c i d secretion. O n p l a t e a u s t i m u l a t i o n o b t a i n e d b y c o n t i n u o u s i.v. i n f u s i o n o f P g a t c o n c e n t r a t i o n p r o d u c i n g 30% o f the m a x i m a l acid response, the e f f e c t s o f b o l u s i n j e c t i o n o f O X M a n d K A 8 w a s s t u d i e d e i t h e r a l o n e o r in c o m b i n a t l o n w i t h SM. S M w a s u s e d at a d o s e b e l o w the t h r e s h o l d (O. 3 ~ m o l / k g ). T h e i n h i b i t i o n o b s e r v e d w a s e x p r e s s e d as a % o f p l a t e a u acid. OXM KA8 nmol/kg .02 .04 .08 nmol/kg I0 15 -SM +SM
16 ± 9 54 ± 3.7
32 • 2 . 4 6 4 t 2.6
50 • 1.8 89 ¢ 1.3
-SM +SM
23 ¢ 4 45 ± 6
49 t 8 65 t 6
O u r d a t a c l e a r l y i n d i c a t e that at a d o s e w h i c h is b y i t s e l f w i t h o u t effect, S~( i n d u c e s a p o t e n t i a t i o n o f the i n h i b i t o r y e f f e c t o f O X M o n P g - s t i m u l a t e d a c i d secretion. 514 e n h a n c e s the e f f e c t o f KA8; in addition, a p r o l o n g a t i o n b y 50 L t n o r m o r e o f this i n h i b i t i o n w a s noticed. W h a t e v e r the m e c h a n i s m s involved, the o b s e r v e d s y n e r g i s t i c e f f e c t s o f O X M and S M s u g g e s t that S M is a p h y s i o l o g i c a l m o d u l a t o r o f the a c t i o n o f O X M in the r e g u l a t i o n o f g a s t r i c acid secretion.
E F F E C T OF V I P O N SRIF R E L E A S E F R O M RAT H Y P O T H A L A M U S : D I F F E R E N T I A L R E S P O N S E S OF FETAL AND ADULT TISSUE L. T a ~ i a - A r a n c i b i a , J. E~elbaum, A. Szafarcz~k,S. A r a n c i b L ~ G. Alonso, H. A s t i e r Lab of N e u r o e n d o c r i n o l o g y C, U A 639 CNRS F. 34060 Montpellier and Lab of N e u r o e n d o c r i n o l o g y , U 159 INSERM F. 75014 Paris. We h a v e p r e v i o u s l y r e p o r t e d that V I P i n h i b i t s the release of SRIF from slices of m e d i o b a s a l h y p o t h a l a m u s (MBH) in a d u l t rats (Epelbaum et al., Eur. J. Pharmacol, 5_88, 493, 1979). In contrast, V I P s t i m u l a t e s SRIF r e l e a s e from d i s p e r s e d d i e n c e p h a lic cells in c u l t u r e (Tapia-Arancibia and Reichlin, B r a i n Res, in press). To inv e s t i g a t e if p e r i n a t a l changes in the SRIF r e s p o n s e to VIP could e x p l a i n these o p p o s i t e e f f e c t s , t w o a p p r o a c h e s w e r e p e r f o r m e d : a/ in v i t r o : b y i n c u b a t i o n of MBH slices of fetal rats (day-3) and of n e o n a t a l rats (day 4 and day 15). The tissues w e r e i n c u b a t e d in L o c k e m e d i u m for Io min (with or w i t h o u t VIP), after a 40 m i n p r e i n c u b a t i o n period. SRIF was m e a s u r e d by RIA. b / in v i v o in c o n s c i o u s a d u l t rats, b y p e r f u s i o n of the m e d i a n e m i n e n c e (ME) u s i n g a p u s h - p u l l c a n n u l a in c o m b i n a t i o n w i t h a c a n n u l a i m p l a n t e d into the lateral v e n t r i c l e for V I P or saline injections. The ME was p e r f u s e d (20 ~i/min) w i ~ a r t i f i c i a l CSF and SRIF o ~ t p u t 6 m e a s u r e d in samples c o l l e c t e d e v e r y 15 min. R e s u l t s : in vitro, V I P (10 - 8 a n d 1 0 - M) s i g n i f i c a n t l y i n c r e a s e d SRIF release from fetal MEH. Data e x p r e s s e d as SRIF released in the m e d i u m in p e r c e n t of SRIF tissue c o n t e n t were: 2.39+0.72 and 3.34+1.O2 respectively, vs 1.22+O.35 in controls. In contrast, VIP did not stimulate SRIF r e l e a s e in n e o n a t a l rats: 0 . 3 0 + 0 . 0 7 and 0 . 8 2 + 0 . 4 0 vs 1.23+O.38 (day 4);O.54+O.21 and 1.O4+O.14 vs O . 9 3 + 0 . 1 4 (day 15).In vivo, IVT i n j e c t i o n of VIP (10 ~g/iO-~l) s t r o n g l y i n h i b i t e d SR~F o u t p u t from the ME w i t h i n 15 min, c o n f i r m i n g our p r e v i o u s in v i t r o data. C o n t r o l rats (10 ~i saline) e x h i b i t e d a normal p a t t e r n of p u l s a t i l e SRIF release. In addition, b y i m m u n o c y t o c h e m [ s t r y , we have o b s e r v e d n u m e r o u s VIPaxonal s y n a p t i c junctions on d e n d r i t e s in the p e r i v e n t r i c u l a r nucleus. Our d a t a s u g g e s t that rIP is a s t i m u l a t o r y factor of SRIF release d u r i n g the p r e n a t a l per i o d , d e v e l o p i n g later into an i n h i b i t o r y one. T h e s e findings indicate that VIP effects d e p e n d o n the m a t u r i t y of the h y p o t h a l a m u s .
SOMATOSTATIN EMHANCES THE INHIBITORY EFFECT OF GLUCAGON-37/O~DULIN (O X M ) A N D O F ITS C - T E R M I N A L O C T A P E P T I D E O N A C I D SECRETION. M. Dubrasquet~, M.-P. A u d o u s s e t - P u e c h z , J. MartinezZ, D. B a % a i l l e a I I N S E R M U.IO, PARIS, & a C e n t r e d e P h a r m a c o l o g i e - E n d o c r i n o l o g i e , MO~,'v~..T.IER, France. I n the a n e s t h e t i z e d rat, O X M is a p o t e n t a n d e f f i c i e n t i n h i b i t o r o f g a s t r i c a c i d s e c r e t i o n s t i m u l a t e d b y P e n t a g a s t r i n (P g ) I the C-terntinal octal)el)tlde o f O X M (K A S ) i n h i b i t s t h l s s t i m u l a t e d g a s t r i c secretion. In the s a m e model, e v i d e n c e w a s p r o d u c e d that S o m a t o s t a t i n (SM) i n h i b i t s g a s t r i n s t i m u l a t e d a c i d secretion. O u r p u r p o s e w a s to i n v e s t i g a t e the e f f e c t o f a s s o c i a t i o n s O X M + ~ 4 and K A 8 + S M o n the s t i m u l a t e d a c i d secretion. O n p l a t e a u s t i m u l a t i o n o b t a i n e d b y c o n t i n u o u s i.v. i n f u s i o n o f P g a t c o n c e n t r a t i o n p r o d u c i n g 30% o f the m a x i m a l acid response, the e f f e c t s o f b o l u s i n j e c t i o n o f O X M a n d K A 8 w a s s t u d i e d e i t h e r a l o n e o r in c o m b i n a t l o n w i t h SM. S M w a s u s e d at a d o s e b e l o w the t h r e s h o l d (O. 3 ~ m o l / k g ). T h e i n h i b i t i o n o b s e r v e d w a s e x p r e s s e d as a % o f p l a t e a u acid. OXM KA8 nmol/kg .02 .04 .08 nmol/kg I0 15 -SM +SM
16 ± 9 54 ± 3.7
32 • 2 . 4 6 4 t 2.6
50 • 1.8 89 ¢ 1.3
-SM +SM
23 ¢ 4 45 ± 6
49 t 8 65 t 6
O u r d a t a c l e a r l y i n d i c a t e that at a d o s e w h i c h is b y i t s e l f w i t h o u t effect, S~( i n d u c e s a p o t e n t i a t i o n o f the i n h i b i t o r y e f f e c t o f O X M o n P g - s t i m u l a t e d a c i d secretion. 514 e n h a n c e s the e f f e c t o f KA8; in addition, a p r o l o n g a t i o n b y 50 L t n o r m o r e o f this i n h i b i t i o n w a s noticed. W h a t e v e r the m e c h a n i s m s involved, the o b s e r v e d s y n e r g i s t i c e f f e c t s o f O X M and S M s u g g e s t that S M is a p h y s i o l o g i c a l m o d u l a t o r o f the a c t i o n o f O X M in the r e g u l a t i o n o f g a s t r i c acid secretion.