Mechanisms of Renal Release of Renin by Electrical Stimulation of the Brainstem in the Cat

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Abstract
Electrical stimulation of the dorsolateral pons for 5-minute periods in anesthetized cats produced a rise in blood pressure of 40%, a reduction in renal blood flow of 28%, and an increase in the rate of renin release (the product of renal plasma flow and the venoarterial difference of plasma renin activity) of more than 100% in intact kidneys. Comparison of an intact kidney with the contralateral denervated one showed that denervation abolished the decrease in renal blood flow and the increase in renin release induced by pontine stimulation. Infusion of phenoxybenzamine into an otherwise intact kidney prevented the decrease in renal blood flow on that side, but brain-induced renin release was at least equal to that from the contralateral kidney in which the vasomotor response remained unchanged. Treatment of the animal with intravenously administered propranolol (1.3-3.0 mg/kg) abolished any rise in renin release, although propranolol accentuated the reduction in renal blood flow during stimulation of the brainstem. We concluded that the increased renal release of renin induced by electrical stimulation of a pressor area of the brainstem was dependent on intact renal nerves and on mechanisms blocked by propranolol but was not dependent on changes in renal blood flow or on renal alpha receptors.