Abstract
The effects of the recently developed 5-HT id receptor antagonist, GR127935 ( N-[4-methoxy-3-(4-methyl-1-piperazinyl)phenyl]-2′-methyl-4′-(5-methyl-1,2,4-oxadiazol-3-yl)[1,1,-biphenyl]-4-carboxamide), and those of the preferential human 5-HT 1Da receptor antagonist, ketanserin, on the isometric contraction induced by 5-hydroxytryptamine (5-HT) and sumatriptan in endothelium-denuded ring segments of canine coronary artery were analyzed. Sumatriptan mimicked 5-HT with lower potency but similar efficacy. GR127935 (1, 3 and 10 nM) concentration dependently antagonized the contractions elicited by both agonists; only the 5-HT maximum was reduced. Ketanserin and mianserin (both at 1 μM) were inactive. These data strongly suggest that a 5-HT id receptor mediates contraction in the dog coronary artery. The possibility that this 5-HT id receptor resembles the cloned human 5-HT idβ subtype is discussed.
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