Resistance of noradrenaline in blood vessels to depletion by 6‐hydroxydopamine or immunosympathectomy

Abstract

The degree of the decrease in the noradrenaline concentrations caused by 6‐hydroxydopamine or immunosympathectomy was different in different areas of the cardiovascular system. In rats or guinea‐pigs 6‐hydroxydopamine depleted the noradrenaline content of the heart by 90%, of the mesenteric vein by 80% and of the mesenteric artery and aorta by 30–60%. Immunosympathectomy elicited a 70% reduction in the cardiac noradrenaline but only a 50% reduction in the noradrenaline of the blood vessels of the rat. The tyrosine hydroxylase activity of the heart, blood vessels, or adrenal glands was not significantly altered 2 weeks after 6‐hydroxydopamine. Nor was the monoamine oxidase activity in heart or blood vessels changed. The inconsistent ability of both 6‐hydroxydopamine and immunosympathectomy to abolish experimental hypertension may be due to the partial persistence of noradrenaline and functional sympathetic nervous system activity in the blood vessels. 1972 British Pharmacological Society