The effect of bilateral adrenal demedullation on vascular reactivity and blood pressure in spontaneously hypertensive rats.

Bilateral adrenal demedullation of juvenile spontaneously hypertensive rats attenuated, but did not prevent, the development of hypertension. Neither did it affect the subsequent vascular reactivity to phenylephrine though it significantly reduced the vascular effects of sympathetic nerve stimulation. Demedullation of adult spontaneously hypertensive rats did not alter blood pressure, but did attenuate the pressor responses to both alpha-adrenoceptor agonists and sympathetic nerve stimulation. In acutely demedullated adult rats, vascular reactivity to sympathetic nerve stimulation, but not to exogenous amines, could be restored by slow i.v. infusion of adrenaline in a dose-dependent manner. The results support a possible facilitatory role for adrenaline in sympathetic neurotransmitter release, both during the development of genetic hypertension and in vascular responses to sympathetic nerve stimulation.