Clonidine antagonism of angiotensin-related drinking: a central site of action.
Administration of either isoproterenol (25 micrograms/kg, s.c.) or angiotensin II (200 micrograms/kg, s.c.) induces drinking in rats within 0.5-1 h. This drinking was inhibited by prior administration of the presynaptic alpha-adrenergic agonist clonidine (12 micrograms/kg, i.p.). Urine output was enhanced by clonidine in the angiotensin II-, but not the isoproterenol-treated group. Drinking in response to peripheral administration of either angiotensin II or isoproterenol was also inhibited by intracerebroventricular (i.v.t.) administration of clonidine (8 micrograms/kg). This dose of clonidine also enhanced the urine output after angiotensin II. Further, the drinking induced by i.v.t. administration of angiotensin II, at 4 but not 20 ng/kg was inhibited by peripheral administration of clonidine (12 micrograms/kg, i.p.). When clonidine was administered i.v.t. prior to i.v.t. injection of either angiotensin II (20 ng/kg) or carbachol (1.2 micrograms/kg), the drinking response to these dipsogens was attenuated. These results suggest that clonidine may act centrally to attenuate drinking at a site, possibly in the nucleus tractus solitarius, that may be considered a final common pathway for this response.
D000804:Angiotensin II / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000187:drug effects*; D002217:Carbachol / Q000494:pharmacology; D003000:Clonidine / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004326:Drinking / Q000187:drug effects*; D005260:Female; D007276:Injections, Intraventricular; D007545:Isoproterenol / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects; D014882:Water-Electrolyte Balance / Q000187:drug effects
D011942:Receptors, Adrenergic, alpha; D000804:Angiotensin II; D002217:Carbachol; D007545:Isoproterenol; D003000:Clonidine