Anal and rectal motility responses to distension of the urinary bladder in the cat.

The neural pathways and possible transmission mechanisms of the integrated autonomic nervous control of the urinary bladder and anorectum, were investigated in chloralose anaesthetized cats. Bladder distension and spontaneous detrusor contractions increased internal anal sphincter-tone, a response which was blocked by an alpha-adrenoceptor antagonist. Moreover, a nicotinic transmission step was present. Both the afferent and efferent limbs of the reflex were conveyed in the postganglionic hypogastric nerves and the preganglionic lumbar splanchnic nerves. Intact connection with the central nervous system was therefore essential. Contrasting to the specific reflex response in the internal anal sphincter, bladder distension also elicited a nociceptive vaso-pressor response. Rectal motility appeared to be unaffected by bladder distension.