Effect on efferent cardiac vagal nerve fibres of distension of the urinary bladder in the dog.

In dogs anaesthetized with chloralose, the effect of distension of the urinary bladder on the activity in efferent vagal nerves was studied; the urinary bladder was distended with warm saline, and the carotid sinuses were vascularly isolated and perfused with blood at constant flow. In one group of efferent vagal nerve fibres distension of the bladder always caused a decrease in activity. These fibres also responded to stimulation of receptors in the carotid region by an increase in activity and to stimulation of superficial branches of the left radial nerve by a decrease in activity. Another group of vagal nerve fibres which did not respond to stimulation of receptors in the carotid region, also did not respond to distension of the urinary bladder. It is concluded that distension of the urinary bladder results in the response of a decrease in activity in efferent cardiac vagal nerve fibres, onto which converge the effects of stimulating receptors in the carotid region and the somatic nerves.