The urethral resistance to rapid dilation: an analysis of the effect of autonomic receptor stimulation and blockade and of pudendal nerve blockade in healthy females.

The urethral closure function is based upon permanently as well as adjunctively acting closure forces during rest and stress episodes, respectively. During urine ingression intra- and peri-urethral structures are suddenly stretched resulting in a pressure response which strengthens the closure function by sustaining the resistance to dilatation of the urethra. A method for measurement of the resistance to rapid urethral dilatation was used to evaluate the influence of noradrenaline, prazosin, terbutaline, propranolol, carbachol, and atropine, as well as bilateral pudendal nerve blockades in 40 healthy women. The drugs caused no significant change in the urethral resistance to dilatation, whereas the pudendal blockade produced a significant (p < 0.05) reduction at the bladder neck and in the high pressure zone. Although a quantitative assessment of their contribution cannot be obtained from this study, it may be concluded that the striated muscles innervated by the pudendal nerve are of major importance for the urethral resistance to dilatation.