The responses in renal nerves to stimulation of atrial receptors, carotid sinus baroreceptors and carotid chemoreceptors.

The reflex reduction in activity in renal sympathetic nerves in response to distension of small balloons in the pulmonary vein-atrial junctions was studied in dogs anaesthetized with chloralose; the carotid sinuses were isolated and perfused with blood. In the first group of dogs, the response to distension of the balloons was studied at different levels of carotid sinus pressure. In thirteen preparations of renal nerves in eight dogs the response was not significantly influenced when the mean carotid sinus pressure was changed from 9.5 kPa to 17.5 kPa, despite marked changes in control frequencies of activity in the nerves. In the second group of dogs, the response to distension of the balloons was studied when the carotid sinuses were perfused alternately with arterial and venous blood. In six preparations of renal nerves in five dogs the response was not significantly influenced when the blood perfusing the carotid sinuses was changed, despite marked changes in control frequencies of activity in the nerves. In a third group of dogs, the reflex reduction in activity in renal nerves in response to a step increase in pressure in one carotid sinus was examined at different levels of pressure in the contralateral carotid sinus. In six preparations of renal nerves in five dogs the response to an increase in pressure in one carotid sinus was significantly reduced when the mean pressure in the contralateral sinus was changed from 8.7 kPa to 17.1 kPa. It is concluded that there is no interaction between the projections of atrial receptors and carotid sinus baroreceptors or carotid chemoreceptors in their convergence on the same efferent renal neurones.