Urotensin II inhibits carotid sinus baroreflex in anesthetized male rats.
OBJECTIVE
To study the effects of urotensin II (UII) on the carotid sinus baroreflex (CSB).


METHODS
The functional curve of carotid sinus baroreflex was measured by recording changes in arterial pressure in anesthetized male rats with perfused isolated carotid sinus.


RESULTS
UII at the concentration of 3 nmol/L had no effect on the CSB, while at the concentration of 30, 300 and 3000 nmol/L inhibited the CSB, shifting the functional curve of the baroreflex upward and to the right. There was a marked decrease in peak slope and reflex decrease in blood pressure. These effects of UII were concentration-dependent. Pretreatment with verapamil (an antagonist of the L-type calcium channel, 10 micromol/L) partially eliminated the above effects of UII (300 nmol/L) on the CSB. Pretreatment with BIM-23127 (3 micromol/L), an antagonist of human and rat UII receptors, abolished the actions of UII on the CSB. Pretreatment with NG-nitro-L-arginine methyl ester (L-NAME) 100 micromol/L did not affect the inhibitory effects of UII (300 nmol/L) on the CSB.


CONCLUSIONS
These data suggest that UII exerts an inhibitory action on the isolated CSB. Such an action of UII is predominantly mediated by the UII receptors in vascular smooth muscles, resulting in the opening of L-type calcium channels.
Wu
Yu-ming
YM
Department of Physiology, Institute of Basic Medicine, Hebei Medical University, Shijiazhuang 050017, China. wuym@hebmu.edu.cn
Xue
Hong-mei
HM
Xiao
Lin
L
He
Rui-rong
RR
D000758:Anesthesia; D000818:Animals; D017704:Baroreflex / Q000187:drug effects*; D002346:Carotid Sinus / Q000187:drug effects* / Q000502:physiology; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D014579:Urotensins / Q000494:pharmacology*; D014700:Verapamil / Q000494:pharmacology
C092829:BIM 23127; D010456:Peptides, Cyclic; D014579:Urotensins; C029677:urotensin II; D014700:Verapamil; D019331:NG-Nitroarginine Methyl Ester