Study of the Electrical and Mechanical Activity of the Rectum: An Experimental Study

Abstract

The electrical activity of the rectal detrusor was studied in 13 dogs. 10 electrodes were sutured serially to the rectal and lower sigmoid colon serosa. Electrical activity was recorded for 30 min/day for 10 days. Simultaneous electric and mechanical activity (recorded by a 6-French catheter connected to a pressure transducer) was also recorded with and without rectal distension by a condom balloon. Electrical activity was further determined after annular myotomy performed at different levels in the rectum and lower sigmoid colon. Pacesetter potentials (PP) were recorded from electrodes 3-10. They were triphasic, propagated caudally and had the same frequency and regular rhythm by all electrodes distal to the 3rd one. Frequency was constant in each dog from day to day. PP were accompanied by action potentials (AP) which had inconsistent frequencies and were accompanied by increased rectal pressure. Rectal distension led to an increase in both the frequency and amplitude of PP and AP. Rectal myotomy below the 3rd electrode resulted in PP and AP disappearing distal but not proximal to the cut, excluding the 1st and 2nd electrodes, which did not show activity. The results suggest that PP start at the 3rd electrode, which corresponds anatomically to the rectosigmoid junction (RSJ). AP cause contractile activity along the rectum. It seems that the RSJ is the site of a pacemaker triggering the PP that pace the AP which initiate the rectal contractile activity.

A study of the origin of the electric activity of the rectum: Is it neurogenic or myogenic?

“…A concept of origin and transmission of the electric waves in the rectal wall Considering the ®ndings of the current and previous studies, 1 we postulate that a`pacemaker' exists in the upper rectum triggering impulses which seem to spread in the rectal wall along the myenteric plexus of nerves. A neurotransmitter is probably secreted at the neuromuscular junction.…”

“…Studies have suggested that the PPs start at the rectosigmoid junction triggered by the rectosigmoid pacemaker, and propagate caudally. 1 It was proposed that these waves are responsible for the motile activity of the rectum and that rectal electric activity disorders could lead to rectal dysmotility and defecation disorders. 1 ± 6 However, the exact source of these electric waves is as yet not ascertained.…”

Response of the internal reproductive organs to clitoral stimulation: The clitorouterine reflex

“…[16][17][18][19][20][21] Thus it seems that the uterine electric activity is responsible for inducing the uterine resting tone which is assumed to assist in keeping the uterus in its resting position and shape. The source of these electric waves is controversial.…”

“…Upon cessation of electrical GC stimulation, the uterine SWs reappeared with variables similar to those before electrical GC stimulation. The latency which is the period from the stimulus to the start of the response recorded a mean of 19.472.1 ms (range [17][18][19][20][21][22][23].…”

“…Repeated buffeting of the GC with the pencil electrode was coupled with dis-and reappearance of the electric waves. The [18][19][20][21][22][23][24][25]. No electric waves were recorded from the CU on mechanical GC buffeting.…”