Lack of Directional Selectivity of Cassaine in Excitation of the Medullary Emetic Chemoreceptor Trigger Zone from Blood and Cerebrospinal Fluid in Cats ∗ †

Abstract

Summary

Cassaine sulfate produced emesis in cats when given by intracerebroventricular (0.02 mg in 0.20 ml) and intravenous (0.5 mg/kg) injection with an average latency of 6 min in either case. The emesis elicited through both routes of administration was eliminated after chronic ablation of the chemoreceptor trigger zone in the area post-rema of the medulla oblongata. The emetic response to intravenous cassaine was blocked by pretreatment with intraventricular cassaine. Intravenous deslanoside only partially blocked the emetic activity of intraventricular cassaine. These results indicate that the emetic receptors of the chemoreceptor trigger zone are accessible to cassaine from the blood as well as from the cerebrospinal fluid, and that identical receptor elements are stimulated by the drug through both routes of administration. This lack of directional selectivity of cassaine stands in contrast to the known selectivity of the cardiac glycosides.