Sensory nerves of the intestines: role in control of pyloric region of dogs.

The canine pylorus is the target for a large array of extrinsic and intrinsic nerve-produced effects. Some of them have intermediate nicotinic synapses. In all cases observed so far the final nerve terminals mediating excitation are cholinergic, but those mediating inhibition are both adrenergic and non-adrenergic non-cholinergic. The role of the dense peptidergic innervation is unclear especially in view of the observation that this muscle and its nerves contain receptors to all of those studied (VIP, PHI, GAL, SP, NKA, NKB, CCK, and others. The pylorus is also the target of an important reflex initiated by acid in the duodenal lumen. Our preliminary work suggests that this reflex is initiated by acid induced release of 5HT from the EC cells to act on 5HT receptors on sensory nerves which activate the ascending chain of cholinergic nerves in the myenteric plexus. This same stimulus may also activate other vagal sensory nerves.