Mechanism of the antihypertensive action of clonidine on the pressor response to physostigmine.
Physostigmine (P) was used as a model in anesthetized rats for the development of hypertension by a central cholinergic mechanism. P (25-100 micrograms/kg i.v.) produced a dose-related increase in mean arterial pressure which was inhibited 30 to 90% by preinjection of clonidine (100 micrograms/kg i.v.). This dose of clonidine was without effect on the pressor response to ganglionic stimulation produced by 1,1-dimethyl-4-phenylpipera-zinium iodine. To examine further the central inhibitory effect of clonidine on the pressor response to P, regional brain acetylcholine turnover rate was measured in control and clonidine-pretreated rats. Clonidine significantly reduced turnover in hypothalamus (69%), pons-medulla (43%) and midbrain (39%) but not in striatum or hippocampus. These observations are consistent with an inhibitory effect of clonidine on central cholinergic neurons involved in cardiovascular regulation.
D000109:Acetylcholine / Q000032:analysis; D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology*; D001794:Blood Pressure / Q000187:drug effects*; D001923:Brain Chemistry / Q000187:drug effects; D003000:Clonidine / Q000494:pharmacology*; D004246:Dimethylphenylpiperazinium Iodide / Q000494:pharmacology; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D007031:Hypothalamus / Q000032:analysis; D008297:Male; D008526:Medulla Oblongata / Q000032:analysis; D008636:Mesencephalon / Q000032:analysis; D010830:Physostigmine / Q000494:pharmacology; D011149:Pons / Q000032:analysis; D051381:Rats
D000959:Antihypertensive Agents; D004246:Dimethylphenylpiperazinium Iodide; D010830:Physostigmine; D003000:Clonidine; D000109:Acetylcholine