The responsiveness of alpha 2-adrenergic receptors in hypothalamus of vasopressin-hypertensive rats.
Administration of clonidine produced biphasic changes in the type II inhibitor activity (endogenous inhibitor of protein kinases which specifically regulates phosphorylation mediated by cGMP-dependent system). Small doses of clonidine (10-50 micrograms/kg) produced an increase while large doses (200-1000 micrograms/kg) induced a decrease in the type II inhibitor activity. The both actions of clonidine were greatly reduced in vasopressin hypertensive rats suggesting subsensitivity of alpha 2-adrenergic receptors. Subsensitivity of postsynaptic alpha 2-receptors was also observed in anterior hypothalamus in in vitro experiments. Incubation of anterior and posterior hypothalamic slices with clonidine resulted in concentration-dependent increase in cGMP content and a decrease in the type II inhibitor activity. The clonidine action in anterior hypothalamus of vasopressin-hypertensive rats was greatly reduced. In contrast, the clonidine action in posterior hypothalamus was the same in vasopressin-hypertensive as in the control rats.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D003000:Clonidine / Q000494:pharmacology; D006973:Hypertension / Q000378:metabolism* / Q000503:physiopathology; D007031:Hypothalamus / Q000378:metabolism*; D008236:Lypressin / Q000494:pharmacology; D008297:Male; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects*; D014667:Vasopressins / Q000494:pharmacology*; D015016:Yohimbine / Q000494:pharmacology
D011942:Receptors, Adrenergic, alpha; D014667:Vasopressins; D015016:Yohimbine; D008236:Lypressin; D011494:Protein Kinases; D003000:Clonidine