EFFECT OF MECHANICAL STIMULATION OF THE SKIN ON THE EXTERNAL URETHRAL SPHINCTER MUSCLES IN ANESTHETIZED CATS

Experiments were performed using anesthetized cats to examine the effects of cutaneous stimuli on the external urethral sphincter (EUS) activity and bladder motility, 1) when the bladder volume was changed from low to high, and in the latter case, in the presence or absence of micturition contractions, 2) in different neurological states, viz., in animals with an intact neuraxis and in acute or chronic spinal preparations. In animals with an intact neuraxis, when the volume of the bladder was low, the bladder was quiescent and noxious mechanical stimulation of the perineal skin produced abrupt and marked increases both in vesical pressure and EUS activity. Similar results were observed in acute spinal as well. as chronic spinal animals. The effect of the stimulus was particularly potent in chronic spinal animals. In animals with an intact neuraxis, when the volume of the bladder was increased, rhythmic micturition contractions were produced and noxious stimulation of the perineal skin slowed the frequency of the large rhythmic micturition contractions of the bladder and increased the EUS activity. These effects in animals with an intact neuraxis were substantially similar to those in chronic spinal cats showing synergic states. The effects of these somatic stimuli on the integration and coordination of bladder motility (controlled mainly by the parasympathetic pelvic efferent nerves) and EUS activity (controlled by somatic pudendal efferent nerves) are discussed.