Studies on the loss of sensitivity in smooth muscle.

Specificity of desensitization effect was investigated at guinea pig ileum using the desensitizing agonists acetylcholine, carbachol, histamine, and serotonine. The desensitization with acetylcholine markedly diminished the contraction effects to test doses of all tested agonists. Contrary to acetylcholine, the histamine desensitization is mainly specific, the serotonine desensitization is a complete specific effect. A different influence of the tested agonists on intracellular ions is discussed.