Vagal control of colonic motility in the anaesthetized ferret: evidence for a non-cholinergic excitatory innervation

Spontaneous colonic motility in the urethane-anaesthetized ferret consists of two distinct types of contraction which correspond to the patterns recorded myoelectrically in conscious animals. This motility was abolished or greatly reduced when nervous conduction was prevented in the cervical vagi by cooling to below 4 degrees C. On rewarming the nerves the colonic motility returned, after a short latency, to the pre-cool level. Atropine transiently abolished colonic motility. On its return the motility was significantly reduced but still sensitive to vagal integrity. Thus the atropine-resistant colonic motility was also abolished or markedly reduced by cooling the cervical vagi to below 4 degrees C. On rewarming there was a longer latency for the return of motility compared to that before atropinization. Electrical vagal stimulation produced, after a short latency, large-amplitude colonic contractions. Following atropine, the short-latency response to electrical vagal stimulation was replaced in the majority of animals by a long-latency response whose characteristics were quite different from those of the cholinergic response. These results are consistent with the vagus containing two functional motor pathways to the colon, one to cholinergic post-ganglionic neurones and the other operating via a non-cholinergic mechanism.