The role of the rectal branches of pelvic plexus in defecation and colonic motility in a canine model.

The parasympathetic nerves regulate colonic motility and defecation. The vagal nerve controls the right colon and the pelvic nerve permeates the left colon and rectum via the rectal branches of the pelvic plexus (RBPP). This investigation aimed to measure the functional changes of the colon and rectum after RBPP-transection for over six months. RBPP-transection was performed in 15 dogs. Five dogs each were sacrificed immediately, one month, and six months after RBPP-transection. The stool condition, colorectal transit, defecation reflex, colorectal response to electrical stimulation, and pathological degeneration was investigated prior to, one month after, and six months after RBPP-transection. Four of the 5 dogs observed had loose stool one month after RBPP-transection, and one of the 3 had recovered six months later. Half transit time (HTT) at transverse colon got longer in six of the 8 in one month. Six months later, HTT got shorter in three of the 4 than that of one month. Defecation reflex was not observed one month after RBPP-transection, but noted in two of the 5 six months later. These results may suggest that vagal nerve compensates for the oral site of the left colon after denervation of the pelvic nerve which is originally distributed.