Effect of adrenal demedullation on vascular responses after immunological sympathectomy

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Abstract
Administration of the antiserum developed to the sympathetic nerve-growth factor results in a functional sympathectomy yet leaves adrenal medullary tissue intact. Chronic adrenal demedul-lations were carried out on control and immunologically sympathecto-mized rats in order to assess the role played by the adrenal medulla in influencing the functional status of the cardiovascular system in the sympathectomized animals. In the perfused hindquaters, the duration, but not magnitude, of constrictor responses produced by epinephrine and norepinephrine was increased equally in sympathectomized and demedullated-sympathectonized animals. Although the constrictor effect of tyramine was diminished by sympathectomy, adrenal demedullation did not further reduce the tyramine response. Demedullated-sympathectomized rats alone showed a significant depression of the blood pressure increase produced by administration of the ganglionic stimulant DMPP [dimethylphenylpiperazinium (broxide)]. Vascular resistance in the hindquarters, which was normal in sympathectomized animals, was reduced significantly following adrenal demedullation. It was concluded that the major function of the adrenal medulla in the sympathectomized rat is to preserve constrictor tone in vascular smooth muscle, presumably through the liberation of catechoiamines.