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The role of the vagi in the control of renin secretion was investigated in dogs maintained on a high-salt diet. Renal perfusion pressure was maintained relatively constant by the manipulation of a suprarenal aortic snare. Mean arterial blood pressure (MAP), plasma renin activity (PRA), and packed cell volume (PCV) increased after sinoaortic denervation and cervical vagotomy. Cooling of cervical vagi to 3-5 degrees C had the same effect as vagotomy. There was no change in MAP, PRA, and PCV in sham-operated animals. Propranolol prevented the increase in PRA following sinoaortic denervation and vagotomy, but not that in MAP or PCV. In splenectomized dogs, PCV still showed increases after sinoaortic denervation and vagotomy. It is suggested that the removal of sinoaortic and/or vagal inhibitory effects on the vasomotor center causes increases in sympathetic discharge to the adrenal medulla and the peripheral vessels, and that this in turn leads to the increase in MAP. The increase in sympathetic discharge to the adrenal medulla and the kidney causes the increases in PRA.

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