Origin of rectal electric waves - Further study

PURPOSE: The rectum possesses electric activity in the form of pacesetter and action potentials. In a recent study we suggested that the waves are not initiated by the extrarectal autonomic innervation but might be triggered by a "rectosigmoid pacemaker." It was postulated that the electric signals are transmitted in the rectal wall through either the muscle bundles or enteric nerve plexus. This hypothesis was studied. METHODS: Under anesthesia the abdomens of 15 dogs were opened, and three electrodes were applied to the rectal serosa. Rectal electric activity and pressure were recorded. Rectal denervation was produced by bilateral pelvic ganglionectomy. The effect of adrenergic (phentolamine and propranolol) and cholinergic (atropine sulfate) blocking agents and a smooth-muscle relaxant (drotaverine) on the electromechanical activity of the denervated rectum was evaluated. RESULTS: After pelvic ganglionectomy rectal pressure decreased (P < 0.05), and pacesetter and action potentials exhibited irregular rhythm and amplitude, a condition of "rectoarrhythmia.'' The arrhythmic pattern showed no significant change (P > 0.05) on administration of the adrenergic and cholinergic blocking agents. However, it was abolished when drotaverine was given. CONCLUSION: Electric waves in the rectal wall seem to be transmitted through the muscle bundles and not the enteric nerve plexus, a finding that might assist in developing an appropriate pharmacotherapy for rectal dysmotilities and defecation disorders.