The function of “α- and β-receptors” in the cardiac sphincter mechanism in rabbits

Abstract Sympathomimetics with both α or β activity inhibit the permanent spasm in the cardiac sphincter region in rabbits, which can be induced by cutting both vagi in the neck. The opening fibers for the sphincter region, running in the vagus nerve are preganglionic. The postganglionic mechanism is adrenergic. The normal function of the sphincter region consists in rhythmic opening and closing movements. The rhythm persists after exclusion of diaphrag-matic movements by curare. This reaction closely resembles the effects of isoprenaline when given to vagotomized animals. It is however distinctly different from the reaction obtained with epinephrine or norepinephrine which after a shorter latency than with isoprenaline open the sphincter suddenly so that the lower part of the oesophagus forms a rigid tube, and then close it again. The β-type of reaction is obtained with doses six times lower than with the α-type.