- Email: [email protected]
Blood calcium response to parathyroid hormone injected into the lateral ventricle and the cisterna magna in rats
S109
BLOOD C A L C I U M R E S P O N S E TO PARATHYROID HORMONE INJECTED INT0 T H E L A T E R A L V E N T R I C L E AND T H E C I S T E R N A ~ G N A IN RATS. HIROYASU MATSUI*. SHUJI AOU. JINGYI ~ * . AND TETSURO HORI, Department of P h y s i o l o g y , F a c u l t y of Medicine, gyushu U n i v e r s i t y , Fukuoka 812. Japan. P a r a t h y r o i d hormone (PTH), t h e c a l c i u m - r e g u l a t l n ghormone, h a s been r e c e n t l y found In t h e c e n t r a l nervous system (CNS). The p r e s e n t s t u d y examined t h e e f f e c t of c e n t r a l a d m i n i s t r a t i o n o f r a t PTHI-~4 on t h e blood f r e e c a l c i u m i o n l e v e l (Ca*-) In male r a t s under u r e t h a n e (SOOmg/kg) + a - c h l o r a l o s e (65mg/kg) a n e s t h e sia. PTII i n doses of i n g , lOng, lOOng, l~g, and 5 ~ g , d i s s o l v e d In 1 0 ~ I physiological saline, was i n j e c t e d I n t o t h e l a t e r a l c e r e b r a l v e n t r i c l e (LCV). Blood (0.55mi) was sampled from t h e r i g h t a t r i u m 30 and 5 mln b e f o r e and 15, 30, 60, 120, 180, 240 min a f t e r PTH or s a l i n e i n j e c t i o n . PTH ( l ~ g ) s i g n i f i c a n t l y i n c r e a s e d t h e blood Ca~ l e v e l a t 60 and 120 min a f t e r a p p l i c a t i o n , a s compared with t h e LCV i n j e c t i o n of i 0 ~ I s a l i n e a l o n e . A f t e r LCV i n j e c t i o n o f PTII, blood pII, which i s known to a f f e c t t h e Ca** l e v e l , did n o t d i f f e r from t h e c o n t r o l l e v e l measured a f t e r s a l i n e i n j e c t i o n . I n t r a v e n o u s i n j e c t i o n of l z g of PTH a s well a s a d m i n i s t r a t i o n I n t o t h e e l s t e r n a magna did not cause a s i g n i f i c a n t i n crease. These f i n d i n g s s u g g e s t t h a t PTH In t h e CNS I s i n v o l v e d i n t h e r e g u l a t i o n o f blood Ca** l e v e l s and I t s t a r g e t s i t e s may be l o c a t e d i n t h e s u p r a m e d u l l a r y CNS.
EVIDENCE F O R F U N C T I O N A L DIFFERENCES OF T H E O R G A N U M V A S C U L O S U M L A M I N A E T E R M I N A L I S INVOLVED IN FEBRILE RESPONSE B E T W E E N RABBITS A N D RATS. A K I O M O R I M O T O AND NAOTOSHI MURAKAMI, D e p a r t m e n t of Physiology, Yamaguchi U n i v e r s i t y School of Medicine, Ube, Yamaguchi 755, Japan. It is well k n o w n that the febrile r e s p o n s i v e n e s s of rabbits is s i g n i f i c a n t l y greater than that of rats. We tested the hypothesis that functional differences in the o r g a n u m v a s c u l o s u m laminae terminalis (OVLT) of rats and rabbits accounted for this observation. The OVLT is thought to be the p a t h w a y t h r o u g h w h i c h pyrogen enters the central nervous system. We i n v e s t i g a t e d w h e t h e r h o r s e r a d i s h peroxidase (HRP), a protein w i t h a m o l e c u l a r w e i g h t of 40,000, injected intravenously enters the OVLT of rats and rabbits. A high c o n c e n t r a t i o n of HRP was observed in the rabbit OVLT i0 and 60 min after injection of HRP. In rats, however, the passage of HRP into the OVLT was c o n s i d e r a b l y limited. These results suggest that the OVLT of the rabbit is more permeable than that of the rat. It is possible that differences in the p e r m e a b i l i t y of the b l o o d - b r a i n barrier in this region could e x p l a i n the differences in the sensitivity of these two species to the intravenous injection of a pyrogen.
EFFECTS
OF
CENTRALLY ADMINISTERED ANGIOTENSIN II IN CONSCIOUS SINOAORTIC RA~S. HIROSHI_~KANN~NI~TADASHI N A ~ A M U R A * 2 2 Y O S H I A K I H A Y A S H I D A * 2 A N D HIROSHI YAMASHITA±,De_~artments of&Ph2siol, and&S~----~tems P_~hzsiol. Uni__vv.o__fOcc~p. and Environ. H e a l t h , Y a h a t a n i s h i - k u ± K i t a k y u s h u 8071Japan ~ To examine the influence of arterial baroreceptors on centrally administered angiotensin II (AII)-inducsd responses, cardiovascular, renal sympatheie and drinking responses to i n t r a c e r e b r o v e n t r i c u l a r l y (i.c.v.) administered AII were compared in conscious rats with b a r o r e c e p t o r s intact and with sinoaortic d e n e r v a t i o n (SAD). The denervation was confirmed by the virtual absence of reflex changes in heart rate (HR) and renal sympathetic nerve activity (RSNA) in response to i.v.infusion of p h e n y l e p h r i n e and sodium nitroprusside. Experiments were performed on the 2nd-Sth days after SAD. In rats with baroreceptors i n t a c t , i n j e c t i o n of AII elicited an increase in mean arterial pressure (MAP) and decreases in HR and RSNA. In SAD rats,the pressor response in the MAP was enhanced, RR reversely increased,and the decrease in RSNA still persisted,although the degree of decrease was reduced. Water intake induced by i.c.v.AII was enhanced in SAD r a t s , c o m p a r e d to that of rats with baroreceptors intact. The results suggest that arterial baroreceptors p r o f o u n d l y affect the cardiovascular responses induced by i.c.v. AII without a significant effect on the RSNA response, and tonically inhibit the dipsogenic action of AII by its pressor activity.
DENERVATED(SAD)
BLOOD C A L C I U M R E S P O N S E TO PARATHYROID HORMONE INJECTED INT0 T H E L A T E R A L V E N T R I C L E AND T H E C I S T E R N A ~ G N A IN RATS. HIROYASU MATSUI*. SHUJI AOU. JINGYI ~ * . AND TETSURO HORI, Department of P h y s i o l o g y , F a c u l t y of Medicine, gyushu U n i v e r s i t y , Fukuoka 812. Japan. P a r a t h y r o i d hormone (PTH), t h e c a l c i u m - r e g u l a t l n ghormone, h a s been r e c e n t l y found In t h e c e n t r a l nervous system (CNS). The p r e s e n t s t u d y examined t h e e f f e c t of c e n t r a l a d m i n i s t r a t i o n o f r a t PTHI-~4 on t h e blood f r e e c a l c i u m i o n l e v e l (Ca*-) In male r a t s under u r e t h a n e (SOOmg/kg) + a - c h l o r a l o s e (65mg/kg) a n e s t h e sia. PTII i n doses of i n g , lOng, lOOng, l~g, and 5 ~ g , d i s s o l v e d In 1 0 ~ I physiological saline, was i n j e c t e d I n t o t h e l a t e r a l c e r e b r a l v e n t r i c l e (LCV). Blood (0.55mi) was sampled from t h e r i g h t a t r i u m 30 and 5 mln b e f o r e and 15, 30, 60, 120, 180, 240 min a f t e r PTH or s a l i n e i n j e c t i o n . PTH ( l ~ g ) s i g n i f i c a n t l y i n c r e a s e d t h e blood Ca~ l e v e l a t 60 and 120 min a f t e r a p p l i c a t i o n , a s compared with t h e LCV i n j e c t i o n of i 0 ~ I s a l i n e a l o n e . A f t e r LCV i n j e c t i o n o f PTII, blood pII, which i s known to a f f e c t t h e Ca** l e v e l , did n o t d i f f e r from t h e c o n t r o l l e v e l measured a f t e r s a l i n e i n j e c t i o n . I n t r a v e n o u s i n j e c t i o n of l z g of PTH a s well a s a d m i n i s t r a t i o n I n t o t h e e l s t e r n a magna did not cause a s i g n i f i c a n t i n crease. These f i n d i n g s s u g g e s t t h a t PTH In t h e CNS I s i n v o l v e d i n t h e r e g u l a t i o n o f blood Ca** l e v e l s and I t s t a r g e t s i t e s may be l o c a t e d i n t h e s u p r a m e d u l l a r y CNS.
EVIDENCE F O R F U N C T I O N A L DIFFERENCES OF T H E O R G A N U M V A S C U L O S U M L A M I N A E T E R M I N A L I S INVOLVED IN FEBRILE RESPONSE B E T W E E N RABBITS A N D RATS. A K I O M O R I M O T O AND NAOTOSHI MURAKAMI, D e p a r t m e n t of Physiology, Yamaguchi U n i v e r s i t y School of Medicine, Ube, Yamaguchi 755, Japan. It is well k n o w n that the febrile r e s p o n s i v e n e s s of rabbits is s i g n i f i c a n t l y greater than that of rats. We tested the hypothesis that functional differences in the o r g a n u m v a s c u l o s u m laminae terminalis (OVLT) of rats and rabbits accounted for this observation. The OVLT is thought to be the p a t h w a y t h r o u g h w h i c h pyrogen enters the central nervous system. We i n v e s t i g a t e d w h e t h e r h o r s e r a d i s h peroxidase (HRP), a protein w i t h a m o l e c u l a r w e i g h t of 40,000, injected intravenously enters the OVLT of rats and rabbits. A high c o n c e n t r a t i o n of HRP was observed in the rabbit OVLT i0 and 60 min after injection of HRP. In rats, however, the passage of HRP into the OVLT was c o n s i d e r a b l y limited. These results suggest that the OVLT of the rabbit is more permeable than that of the rat. It is possible that differences in the p e r m e a b i l i t y of the b l o o d - b r a i n barrier in this region could e x p l a i n the differences in the sensitivity of these two species to the intravenous injection of a pyrogen.
EFFECTS
OF
CENTRALLY ADMINISTERED ANGIOTENSIN II IN CONSCIOUS SINOAORTIC RA~S. HIROSHI_~KANN~NI~TADASHI N A ~ A M U R A * 2 2 Y O S H I A K I H A Y A S H I D A * 2 A N D HIROSHI YAMASHITA±,De_~artments of&Ph2siol, and&S~----~tems P_~hzsiol. Uni__vv.o__fOcc~p. and Environ. H e a l t h , Y a h a t a n i s h i - k u ± K i t a k y u s h u 8071Japan ~ To examine the influence of arterial baroreceptors on centrally administered angiotensin II (AII)-inducsd responses, cardiovascular, renal sympatheie and drinking responses to i n t r a c e r e b r o v e n t r i c u l a r l y (i.c.v.) administered AII were compared in conscious rats with b a r o r e c e p t o r s intact and with sinoaortic d e n e r v a t i o n (SAD). The denervation was confirmed by the virtual absence of reflex changes in heart rate (HR) and renal sympathetic nerve activity (RSNA) in response to i.v.infusion of p h e n y l e p h r i n e and sodium nitroprusside. Experiments were performed on the 2nd-Sth days after SAD. In rats with baroreceptors i n t a c t , i n j e c t i o n of AII elicited an increase in mean arterial pressure (MAP) and decreases in HR and RSNA. In SAD rats,the pressor response in the MAP was enhanced, RR reversely increased,and the decrease in RSNA still persisted,although the degree of decrease was reduced. Water intake induced by i.c.v.AII was enhanced in SAD r a t s , c o m p a r e d to that of rats with baroreceptors intact. The results suggest that arterial baroreceptors p r o f o u n d l y affect the cardiovascular responses induced by i.c.v. AII without a significant effect on the RSNA response, and tonically inhibit the dipsogenic action of AII by its pressor activity.
DENERVATED(SAD)