The role of pelvic and perineal striated muscles in urethral function during micturition in female rabbits

Abstract

Aim: To evaluate the role of pelvic and perineal striated muscles on urethral function during micturition.

Methods: Pubococcygeus, or both bulbospongiosus and ischiocavernosus muscles were electrically stimulated during the voiding phase of micturition, and bladder and urethral pressure were simultaneously recorded in urethane anesthetized female rabbits. Bladder and urethral function were assessed measuring urodynamic and urethral pressure variables obtained before and during the stimulation of muscles. Two-tail paired t-tests were carried out in order to determine significant differences (P < 0.05) between groups.

Results: Electric stimulation of the pubococcygeus during voiding decreased voiding efficiency and voided volume, whereas residual volume, the duration of voiding, the interval between bladder contraction and urethral resistance increased. Simultaneously, there was an increase in maximum urethral pressure, as well as an increase in the pressure to return to baseline and in the pressure required to close the urethra. Electrical stimulation of bulbospongiosus and ischiocavernosus muscles increased voiding efficiency, voiding duration, and the maximal pressure in bladder. Meanwhile, the maximal urethral pressure, the time related to the rise of urethral pressure, and the urethral pressure required to close the urethra decreased.

Conclusions: The stimulation of pelvic and perineal muscles have opposing roles in urethral function during micturition. Pubococcygeus muscles facilitate urethral closure, while they inhibit bladder contraction. In contrast, bulbospongiosus and ischiocavernosus muscles prevent urethral contraction while they promote bladder contraction.

Keywords: lower urogenital tract; pelvic floor; perineum; urodynamics.