Inhibition by morphine of the release of acetylcholine from the intestine of the guinea-pig.

In experiments on the isolated small intestine of the guinea-pig, morphine inhibited the release of acetylcholine (ACh) into the bath fluid. Experimental evidence is presented which suggests that the reduced release of ACh could not be explained by an inhibition of the synthesis of ACh, nor by stabilization of the bound form of ACh in the tissue. Apparently morphine reduces the excitability of postganglionic structures and thereby the liberation of ACh from nerve endings during the process of excitation.