Antihypertensive effects of ketanserin in the spontaneously hypertensive rat: mode of action.

In the spontaneously hypertensive rat (SHR), ketanserin and the ketanserin analogues R56413 and ritanserin were studied with regard to their ability to reduce the blood pressure in conscious rats and shift the dose-response curves for phenylephrine and serotonin (5-HT) in pithed rats after acute administration. There was a striking correlation between the degree of hypotension and the degree of inhibition of the phenylephrine-induced pressor responses. 5-HT2-receptor blockade alone by ritanserin did not influence the blood pressure but it potentiated the hypotensive response to alpha 1-adrenoceptor blockade by prazosin. Thus, following acute administration in the SHR, the major portion of the antihypertensive response to ketanserin is due to an alpha 1-adrenoceptor blockade but the 5-HT2-receptor blockade may contribute.