Abstract
In chloralose-anaesthetized and artificially ventilated dogs, the carotid sinuses were vascularly isolated and perfused with arterial blood. Mean aortic pressure was held constant at 100 +/- 2 mmHg (mean +/- S.E. of mean, n = 19) by means of a pressure bottle connected to the aorta. Both vagus nerves were sectioned in the neck and propranolol hydrochloride (0.5 mg kg-1) was administered every 30 min. The left renal blood flow was measured by an electromagnetic flowmeter (wrap-round probe), glomerular filtration rate by creatinine clearance and urinary sodium by flame photometry. Decreasing pressure in the isolated carotid sinuses from 186 +/- 10 to 63 +/- 5 mmHg resulted in significant decreases in renal blood flow from 281 +/- 35 to 177 +/- 30 ml min-1 100 g-1 renal mass; glomerular filtration rate from 40.0 +/- 7.8 to 12.3 +/- 4.4 ml min-1 100 g-1; urine flow from 0.31 +/- 0.05 to 0.12 +/- 0.03 ml min-1 100 g-1 and sodium excretion from 21.7 +/- 7.2 to 8.2 +/- 3.0 mumol min-1 100 g-1. Increasing carotid sinus pressure back to 188 +/- 11 mmHg resulted in increases in all the variables to values not significantly different from their initial values. Tying renal sympathetic nerves at low carotid sinus pressure (73 +/- 11 mmHg) caused an increase in all of the variables. After denervation there was no response to changes in carotid sinus pressure. These results show that changes in carotid sinus pressure can result in significant reflex effects on renal function and that these effects are mediated by renal sympathetic nerves.