Ketanserin and the arterial baroreceptor reflex in normotensive subjects.

The effects of oral ketanserin 40 and 120 mg on the responses to baroreflex activation and deactivation by phenylephrine and nitroglycerin, respectively, were investigated in normotensive subjects. Plasma catecholamine levels were measured at the same times. Two hours after the administration of ketanserin, and regardless of its effect on arterial pressure (no change after 40 mg, decrease after 120 mg), there was no alteration either in resting heart rate or baroreflex sensitivity during baroreceptor activation or deactivation. The lack of reflex tachycardia in response to the drug-induced hypotension may be related to the alpha 1-adrenoceptor blockade-mediated sympathoinhibitory effect of ketanserin, which leaves unaffected both plasma catecholamines and the normal reactivity of the sympathetic system.