Effects and mechanisms of vaginal electrical stimulation on rectal tone and anal sphincter pressure

PURPOSE: This study was designed to evaluate the effect of vaginal electrical stimulation on rectal tone and compliance and anal sphincter pressure and to explore possible mechanisms involved in the effects of vaginal electrical stimulation on rectal tone in conscious dogs. METHODS: Seven dogs inserted with a probe with two ring electrodes were studied. The study included two experiments. The first experiment was composed of two series of sessions rectal tone and compliance; and anal sphincter pressure. Each series included three sessions: vaginal electrical stimulation with long pulses, vaginal electrical stimulation with trains of long pulses, and vaginal electrical stimulation with trains of short pulses. The second experiment was performed in two sessions: vaginal electrical stimulation with long pulses plus guanethidine, and vaginal electrical stimulation with trains of long pulses plus guanethidine. In each session, rectal tone was recorded. RESULTS: 1) Vaginal electrical stimulation with long pulses or trains of long pulses but not trains of short pulses significantly decreased rectal tone and increased anal sphincter pressure. 2) None of the vaginal electrical stimulation methods altered rectal compliance. 3) The inhibitory effect of vaginal electrical stimulation on rectal tone was abolished by guanethidine. CONCLUSIONS: Vaginal electrical stimulation with long pulses or trains of long pulses but not trains of short pulses reduces rectal tone and increases anal sphincter pressure. The inhibitory effect of vaginal electrical stimulation on rectal tone is mediated by the sympathetic pathway. These findings suggest that vaginal electrical stimulation may be a potential therapy for fecal incontinence.