Cardiovascular effects in the rat of ketanserin, a novel 5-hydroxytryptamine receptor blocking agent

Following intravenous administration of ketanserin (0.3-10 mg kg-1) to conscious or anaesthetized normotensive and spontaneously hypertensive rats there were dose-dependent blood pressure reductions but no compensatory tachycardia. Intracerebroventricular administration of ketanserin (25-500 microgram) had inconsistent and largely insignificant cardiovascular effects. In a dose range where it produces hypotension ketanserin antagonized the pressor responses to adrenaline and noradrenaline as well as to 5-hydroxytryptamine in monoamine depleted and spinalized rats. It is suggested that the hypotensive action of ketanserin in the rat does not involve a central mechanism but a peripheral alpha-adrenolytic action is implicated.