Contribution of Baroreceptors to the Control of Renal Function.

• In experiments undertaken to produce acute hypertension by left stellate ganglion stimulation, it was observed that during such stimulation a diuresis occurred which was not related to changes in mean arterial pressure. In fact, diuresis was sometimes observed in animals in which mean arterial pressure remained the same or declined. During the diuresis, a decline in left atrial pressure was also observed. According to the atrial volume receptor hypothesis,' a decline in left atrial pressure should decrease the rate of discharge in atrial afferent nerves and increase the secretion of the antidiuretic hormone and decrease urine flow. In view of these preliminary observations it appeared worthwhile to undertake more definitive experiments to determine the cause of the diuresis observed during stellate ganglion stimulation. The results of these experiments indicate that the diuresis is reflex in nature, the stimulus appearing to be the increase in arterial pulse pressure induced by stimulation of the cardiac sympathetic efferent nerves. This increase in pulse pressure presumably stimulates the baroreceptors, subsequent to which there occurs a reflex diminution of activity in the renal sympathetic efferent nerves. This in turn leads to an increase in glomerular filtration rate and water and electrolyte excretion. During these experiments it was noted that little or no change in urine flow occurred when renal nerve activity was increased reflexly by carotid artery occlusion 3 despite substantial increases in renal arterial blood pres-