The effect of distension of the urinary bladder on activity in efferent vagal fibres in anaesthetized dogs.

Experiments were performed in anaesthetized dogs to find out whether the response of decreases in vagus nerve activity to distension of the urinary bladder is affected by changes in carotid sinus pressure. The carotid sinuses were vascularly isolated and perfused with blood at constant flow. Both ureters were cannulated and the urinary bladder was distended with warm Ringer solution. In eight dogs, all eleven efferent vagus fibres which responded to changes in carotid sinus pressure also responded to distension of the urinary bladder by a decrease in activity. This response of a decrease in activity was obtained at all levels of carotid sinus pressure between 8.4 and 30 kPa, and was greater at high than at low carotid sinus pressure. In the same vagus fibres, a relation was shown between progressive decreases in activity and either increases in intravesical pressure up to 8.7 kPa or reductions in carotid sinus pressure between 9 and 30 kPa. The decreases in activity were greater at high than at low carotid sinus pressure. These findings have shown that the inhibition of vagus nerve activity caused by bladder distension was affected by the level of carotid sinus pressure.

The effect of distension of the urinary bladder on activity in efferent renal fibres in anaesthetized dogs.

1. To test whether distension of the urinary bladder causes a consistent change in activity in efferent renal nerve fibres, bladder distension was performed in anaesthetized dogs. The carotid sinuses were vascularly isolated and perfused with blood at constant flow. Both ureters were cannulated and the urinary bladder was distended with warm Ringer solution at a steady intravesical pressure. 2. In a first series of experiments all twenty-six renal nerve fibres in eleven dogs which responded to changes in carotid sinus pressure and changes in the nature of the blood perfusing the carotid sinuses also responded to distension of the bladder. 3. In a second series of experiments, graded bladder distension over a range of pressure of 0-9.2 kPa led to a graded increase in activity in thirteen efferent renal fibres in six dogs. The magnitude of the renal nerve response was greater at low than at high carotid sinus pressure. Over a range of carotid sinus pressure of 9-30 kPa, the greatest renal nerve activity was obtained at the lower end of this range in the presence of bladder distension. 4. Thus distension of the urinary bladder resulted in the response of a consistent increase in efferent renal nerve activity, which could be graded according to intravesical pressure. The magnitude of the responses to bladder distension was affected by carotid sinus pressure.