Locus of the Central Emetic Action of Cardiac Glycosides. ∗

Abstract

Summary

Experiments on dogs have revealed the existence of a chemoreceptor trigger zone for emesis which is quite distinct from the vomiting center. This zone is a bilateral structure situated at the surface of the medulla oblongata in the dorsal region of the ala cinerea. Destruction of the emetic chemoreceptor zone results in animals which are permanently refractory to apomorphine given by vein, but it does not impair the vomiting response to orally administered copper sulfate. Eight out of 9 such dogs failed to vomit when tested intravenously with known emetic doses of the cardiac glycosides, lanatoside C, scillaren A and ouabain. Only one vomiting response was elicited; in this case, the latent period was greatly prolonged, a fact which suggests the existence of another site of emetic action of digitalis glycosides. The significance of a central chemoreceptor trigger zone for the emetic action of digitalis is discussed.