Influence of the endothelium on contractile effects of 5‐hydroxytryptamine and selective 5‐HT agonists in canine basilar artery

Open Access
Publisher Website
Google Scholar
Abstract
1 We have investigated the influence of endothelial damage on the cerebrovascular reactivity to 5-hydroxytryptamine (5-HT) and some selective 5-HT agonists in canine basilar artery. 2 5-HT, α-methyl 5-HT, GR 43175 (3-[2-dimethyl amino] ethyl-N-methyl-lH-indole-5-methane sulphonamide) and 5-carboxamidotryptamine (5-CT) produced concentration-dependent contractions of untreated dog basilar artery with a functional endothelium. Following endothelial damage by perfusion with Triton X-100 (0.1%), which abolished the relaxant response to substance P, the maximum contractile effect of 5-HT, α-methyl 5-HT, GR 43175 and 5-CT was markedly enhanced although there was little change in the EC50 values. Endothelial damage did not modify the vasoconstrictor effect of the thromboxane agonist, U46619, or potassium chloride. 3 Neither 5-HT nor 5-CT caused relaxation of untreated canine basilar arteries contracted with prostaglandin F2α, U46619, uridine triphosphate or potassium chloride. 4 These results suggest that canine basilar artery spontaneously releases endothelium-derived relaxing factor which can attenuate the vasoconstrictor effect of 5-HT and selective 5-HT agonists. This effect appeared to be specific since the vasoconstrictor response to U46619 was not modified. 5 These results demonstrate that the cerebrovascular endothelium can markedly influence the reactivity of the vascular smooth muscle of canine basilar artery to 5-HT and 5-HT1-like receptor agonists. However we could find no evidence that 5-HT receptor activation stimulates endothelial cell function as it does in some other blood vessels.