Vascular reactivity of rats after prevention of hypertension by central administration of 6-hydroxydopamine.

Reactivity to noradrenaline was studied in isolated perfused mesenteric artery preparations from 14-week-old spontaneously hypertensive rats (SHR), DOCA/salt and one-kidney, one clip hypertensive rats as well as in rats which did not develop high blood pressure due to intracerebroventricular (i.c.v.) injection of 6-hydroxydopamine (6-OH-DA) at an age of five to six weeks. The mesenteric arteries from all three types of hypertensive rats showed an increased reactivity to noradrenaline as characterized by a steeper dose-response curve and elevated maximal vasoconstriction when compared with normotensive controls. 6-OH-DA-induced failure to develop DOCA/salt or renal hypertension was associated with vascular reactivity indistinguishable from that of normotensive controls. Mesenteric arteries from 6-OH-DA-treated SHR showed an increased reactivity to noradrenaline but no increase in maximal vasoconstriction. It is concluded that vascular reactivity of SHR to noradrenaline is increased at an age of 14 weeks although elevated blood pressure can be excluded as causative factor.