Evidence for a non-cholinergic excitatory innervation in the control of colonic motility.

The colon of the ferret anesthetized with urethane exhibits two distinct types of motility patterns. These were abolished or considerably reduced by blocking nervous conduction in the vagus nerves by cooling to below 4 degrees C. Atropine transiently abolished motility which on its return was also found to be sensitive to vagal integrity. Electrical stimulation of either the cut central or peripheral end of a branch of the abdominal vagus caused large amplitude contractions of the colon which were not blocked by atropine or by atropine and a combination of alpha- and beta-adrenoceptor blocking agents. These results are consistent with either two separate motor pathways to the colon in the vagus nerve, one cholinergic, the other non-adrenergic, non-cholinergic, or a single pathway with the effects mediated by a primary and a co-transmitter. They also demonstrate that "spontaneous activity" is driven in part by both cholinergic and non-cholinergic mechanisms.