Demonstration of 5-hydroxytryptamine receptors through inhibition by methergoline in cat pial arteries in vitro.

1 In an attempt to characterize further the nature of the 5-hydroxytryptamine (5-HT)-induced contraction of intracranial vessels, cat's middle cerebral artery was exposed to this amine and the specific 5-HT receptor antagonist, methergoline, under standardized conditions in vitro. Methergoline, in increasing concentrations, produced a parallel shift of the log dose-response curve for 5-HT. 2 The Arunlakshana-Schild plot gave a straight line with a slope of -0.85. The figure corresponding to the pA2 value was 8.80. 3 The findings offer further support for the assumption that the 5-HT-induced intracranial vasoconstriction is mediated by specific 5-HT receptors.