Functional and histological effects of intravaginal electrical stimulation on the pelvic muscles: a study in the rat

We studied functional and histological effects of electrical stimulation (ES) on pelvic muscles of the rat. With intravaginal electrodes, the musculus pubococcygeus and musculus iliococcygeus in the awake animal were stimulated three times 6 min per day with 5 min of rest in between, 5 days per week, 7 consecutive weeks with a biphasic rectangular symmetrical current of 25 Hz, 400-mus pulse duration, on/off time of 5/10 and with an amplitude of 2-4 mA. A "sham group" received the same handling but no stimulation. Contraction measured with intra-rectal pressure during stimulation increased more in the stimulated than in the sham group, but did not reach statistical significance probably due to low power. The 2A fast fibres increased with 14% in the musculus iliococcygeus and with 6% in the musculus pubococcygeus. Type 1 slow fibres did not change. Increased capillary density was found after stimulation. Repeated intravaginal ES has mainly an influence on the fast fibres in the pelvic muscles. To influence slow fibres, another stimulation program or current parameters would seem necessary.