Distribution of muscarinic receptors of different affinities in smooth muscle of human stomach

Muscarinic receptors of high and low affinity were found in the fundus and the body of human stomach through the contraction experiment combined with ligand method in vitro. The 2 types of muscarinic receptors with different affinity regulated respectively the contractions of the longitudinal and the circular muscle of human gastric fundus and gastric body. However, in the antrum exists only one kind of muscarinic receptors of high affinity, which regulated the contractions of the longitudinal and the circular muscles of human stomach. The contractile force of the longitudinal muscle induced by exogenous ACh in the fundus and that in the body of human stomach were found to be similar to each other. The contractile force of the circular muscle in the body was found to be the strongest, and the contractile force of both longitudinal and circular muscles in antrum was weaker.