Descending release of acetylcholine from the locally distended guinea pig ileum

The effects of local distension of the intestinal wall on the release of acetylcholine (ACh) from the adjacent non-distended part were studied with the segment os isolated guinea pig ileum. Local distension of the intestinal wall induced the increased release of ACh in the distended part and in its anal side but not in its oral side. Such aboral release of ACh by local distension was abolished by tetrodotoxin or atropine in the concentrations which did not block the release in the distended part. When hexamethonium was applied exclusively to the distending part, significant increase of ACh release was observed in both the regions oral to and anal to the distended part. It is suggested that distension stimuli applied to the myenteric plexus are transmitted aborally along the network of the Auerbach's plexus to the anal direction. The release of ACh from the intestine by nicotine or DMPP differed from the occurring during local distension in that the release was localized to the part of the intestine to which the drug was applied.