Evidence for the involvement of alpha-adrenoceptor blockade in the antihypertensive action of diazoxide in the renal hypertensive rat.

The effects of diazoxide on the blood pressure and heart rate of conscious renal hypertensive rats have been investigated. The antihypertensive action of diazoxide has been studied in relation to the effects of diazoxide pretreatment on pressor responses to stimulation of the complete sympathetic outflow and to injections of noradrenaline, phenylephrine, angiotensin and serotonin in pithed rats. In pithed preparations, pressor responses to sympathetic nerve stimulation, and to injected noradrenaline and phenylephrine were significantly reduced by diazoxide pretreatment, at a time corresponding to maximal reduction of blood pressure in conscious animals. At this time there was no significant reduction of pressor responses to injected angiotensin or serotonin. These findings suggest a contribution of alpha-adrenoceptor blockade to the antihypertensive activity of diazoxide.