Effect of distension of the urinary bladder on efferent cardiac sympathetic nerve fibres which respond to stimulation of atrial receptors.

The effect of distension of the urinary bladder on the activity in the efferent cardiac sympathetic nerves which responded to stimulation of atrial receptors or those which responded to stimulation of carotid baroreceptors or chemoreceptors, was studied in dogs anaesthetized with chloralose; the urinary bladder was distended with warm saline, small balloons were positioned at the right pulmonary vein-atrial junctions and distended with 1 cm3 saline, and the carotid sinuses were vascularly isolated and perfused with blood at constant flow. The efferent cardiac sympathetic nerve fibres which responded to stimulation of carotid baroreceptors and chemoreceptors by a decrease in activity always responded with an increase in activity in response to distension of the urinary bladder. In contrast, in those efferent cardiac sympathetic nerve fibres which did not respond to an increase in carotid sinus pressure, but responded to stimulation of atrial receptors by an increase in activity, distension of the urinary bladder neither caused a significant change in activity nor produced a reproducible pattern of response. It is concluded that the efferent cardiac sympathetic nerve fibres which respond to stimulation of atrial receptors are separate from those which respond to distension of the urinary bladder.