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PubMed · 41494

Effects of clonidine, guanfacine and three imidazolidine derivatives related to clonidine on blood pressure, heart rate and gastric acid secretion in the anaesthetized rat.

I C Medgett·M W McCulloch
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Abstract

The effects of histamine, guanfacine, clonidine (2,6-dichlorophenylimino-2-imidazolidine) and the 2,6-dibromo, 2,3- and 2,5-dichloroanalogues of clonidine were assessed on blood pressure, heart rate and gastric acid secretion in the anaesthetized rat, with lumen-perfused stomach. Histamine (100 microgram/kg to 1 mg/kg) and clonidine (250 microgram/kg to 1 mg/kg) each caused acute increases in acid secretion, the magnitude and duration of which were dose-dependent: the secretory effect of clonidine was blocked by cimetidine (2 mg/kg). Histamine produced a short-lasting hypotension with no effect on heart rate, whereas clonidine produced an initial transient rise followed by a prolonged fall in blood pressure accompanied by a marked bradycardia. Guanfacine and the three clonidine analogues all produced cardiovascular effects similar to those of clonidine; however, only the 2,6-dibromo analogue increased gastric acid secretion. These results confirm previous findings using guinea-pig atria that only imidazolidine derivatives with 2,6-substitution in the phenyl ring activate histamine H2-receptors mediating gastric acid secretion in the rat; this is not so for the hypotensive and bradycardic effects of the compounds.

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AnimalsAntihypertensive AgentsBlood PressureCimetidineClonidineFemaleGastric JuiceGuanidinesHeart RateHistamineHydrogen-Ion ConcentrationImidazolesMalePhenylacetatesRatsJournal Article

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I C Medgett, M W McCulloch. 1979. Effects of clonidine, guanfacine and three imidazolidine derivatives related to clonidine on blood pressure, heart rate and gastric acid secretion in the anaesthetized rat.. https://pubmed.ncbi.nlm.nih.gov/41494/

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