THE MOTOR INNERVATION OF THE COLON

Abstract

A study was made of motor innervation of the colon of the dog, pig and monkey using tandem balloon and balloon-enterograph recording systems; and employing various autonomic drugs. The pelvic nerves to the colon are cholinergic. It is suggested that unequal distribution of pelvic nerve fibers to the muscle layers, and the intracellular ending of certain pelvic nerve fibers explain the discrepancies between the response of the colon to pelvic nerve stimulation and that to the injection of acetyl choline. Electrical stimulation of the pelvic nerves causes longitudinal and circular contraction of the descending and distal colon. These nerves influence upper levels of the colon via nerve pathways located in the wall of the colon. A dual contractile and tonus mechanism in response to pelvic nerve stimulation does not exist in the colon as it has been claimed to exist in the urinary bladder. Electrical stimulation of the vagus nerve is ineffective in producing a response of the colon of the dog. However, in certain instances it may produce a weak and inconstant contraction of a portion of the caecum in the pig and monkey. The hypogastric nerves to the musculature of the colon are adrenergic. Electrical stimulation of these nerves causes a circular contraction which is confined to the distal colon. A response of the colon is not uniformly obtained as a result of stimulating these nerves. The fibers of the coeliac root of the inferior mesenteric ganglia which act on the colon are adrenergic. When they are stimulated electrically a circular contraction which is confined to the descending colon is obtained. A response of the colon is not uniformly obtained as a result of stimulating these nerves.