2-METHYL-5-HT-INDUCED VASOCONSTRICTIONS MEDIATED VIA ALPHA(1)-ADRENOCEPTORS IN RABBIT COMMON CAROTID ARTERIES

We investigated the effects of 2-methyl-5-HT and 1-phenylbiguanide on isolated and perfused rabbit common carotid arteries by a cannula inse rtion method. 1-Phenylbiguanide produced neither vasoconstriction nor dilation. On the other hand, 2-methyl-5-HT produced only a vasoconstri ction, and the dose-response curve was shifted to the right in paralle l by treatment with either ketanserin or bunazosin, although methyserg ide and granisetron had no antagonistic effect. Moreover, the vasocons triction was not inhibited by guanethidine and imipramine. These data showed that 2-methyI-5-HT acts as an alpha(1)-adrenoceptor agonist but not as a 5-HT3-receptor agonist in this vessel.