Afferent pathways and efferent mechanisms in the bladder viscero-vascular reflex.

The afferent and efferent limbs of the bladder viscero-vascular reflex have been studied in cats under chloralose anaesthesia. The maximum change in arterial blood pressure in response to applied tension was obtained from the region of the trigone and bladder neck; lesser responses were obtained from all other regions of the bladder. The response to rapid bladder filling was little affectecd by hypogastric nerve section. Although it was much reduced after section of sacral posterior roots, it was not abolished until higher posterior roots had also been cut, sometimes Up to T 10. In the presence of an intact nervous system, during the early stages of slow bladder filling hind limb vasoconstriction occurred, but there was compensatory limb vasodilation and bradycardia so that no change in blood pressure occurred. Later in the course of filling changes in blood pressure occurred and were associated with vasoconstriction in fore as well as hind limbs and subsequently tachycardia. Occasionally with extreme distension cardiac arrhythmias, such as ventricular or nodlal extra systoles, appeared. There was less compensation when filling was faster, and no compensation after baroreceptor denervation. Cardiac denervation abolished the changes in heart rate, but the circulatory changes in the limbs were unaffected. It is concluded that bladder viscero-vascular reflexes are initiated mainly by tension changes in the region of the trigone and bladder neck; the afferent path can be either the hypogastric or pelvic splanchnic nerves, although the predominant route is the latter; and in the presence of intact baroreceptor reflexes, changes in the circulation occur early and before any alteration in the arterial blood pressure.