Vasoconstrictor mechanism of 5-hydroxytryptamine in isolated and perfused canine basilar arteries

The stainless steel cannula inserting method was applied to investigate the vasoconstrictor mechanism of 5-hydroxytryptamine (5-HT) in isolated and perfused canine basilar arteries. An intraluminal administration of 5-HT induced vasoconstriction in a dose-dependent manner. Pretreatment with ketanserin, a specific 5-HT2 inhibitor, and with methysergide, a mixed 5-HT inhibitor blocked the vasoconstriction induced by 5-HT. Pretreatment with diltiazem, a potent calcium antagonist, also definitely depressed the vasoconstriction by 5-HT, as well as that by potassium chloride (KCl). The endothelial removal by intraluminal saponin treatment little influenced vasoconstriction by 5-HT. It is concluded that 5-HT-induced vasoconstriction of canine basilar arteries may be in part due to the stimulation of 5-HT2 receptors, which activate an intracellular calcium movement, rather than the influx from the extracellular space.