Changes of tissue acetylcholine in the distended intestine.

The effects of distension of the intestinal wall on the liberation and the synthesis of acetylcholine (ACh) were studied in the isolated guinea-pig ileum measuring the changes in the amount of free and bound ACh. In the presence of eserine longitudinal distension increased the amount of bound ACh in the intestinal wall without increasing the free ACh, while circumferential distension or mucosal rubbing increased free but not bound ACh. These effects were evident within 30 sec. In the eserine-free medium the amount of bound ACh was increased in either direction of distension. Addition of more than 5 X 10(-8) g/ml ACh to the bathing medium completely blocked the distension-induced increase. It is concluded that the release and the synthesis of ACh may be both augmented by the circumferential and the longitudinal distension in the physiological conditions. In the presence of eserine, however, the presence of unphysiologically high extracellular ACh levels presumably inhibits the distension-induced augmentation of ACh synthesis in the tissue.