α-Adrenoceptor Subtype in the Hypothalamic Paraventricular Nucleus Involved in the Regulation of Urine Production: Comparison between Wistar Kyoto and Spontaneously Hypertensive Rats
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Microinjections of α-adrenoceptor agonists into the paraventricular nucleus (PVN)of Wistar Kyoto rats (WKY)decreased the urine outflow rate in dose and time-dependent manners. The order of the antidiuretic potency is norepinephrine (an α-agonist)> phenylephrine (an α<SUB>1</SUB>-agonist)>> clonidine (an α<SUB>2</SUB>-agonist). The phenylephrine-induced effect was inhibited by WB4101 (an α<SUB>1</SUB>-antagonist), but not by yohimbine (an α<SUB>2</SUB>-antagonist). <I>d</I>(CH<SUB>2</SUB>)<SUB>5</SUB>-D-Tyr(Et)VAVP (a vasopressin antagonist)blocked the antidiuretic effect of phenylephrine. In spontaneously hypertensive rats (SHR), norepinephrine and phenylephrine produced weaker antidiuretic effects than in WKY. These findings suggest that the α<SUB>1</SUB>-subtype of the PVN decreases urine production mediated through vasopressin release. This mechanism is more feeble in SHR than WKY.
- The Japanese Journal of Pharmacology
The Japanese Journal of Pharmacology 74(1), 95-98, 1997-05-01
The Japanese Pharmacological Society