RILMENIDINE PREVENTS EPINEPHRINE-INDUCED ARRHYTHMIAS IN HALOTHANE-ANESTHETIZED DOGS

Stimulation of central alpha(2)-adrenoceptors has been known to preven t epinephrine-induced arrhythmias in halothane-anesthetized dogs. Beca use recent studies suggested that several physiological processes that were traditionally attributed to activation of alpha(2)-adrenoceptors , such as hypotensive action, are mediated through imidazoline recepto rs (IRs), it may be likely that IRs are involved in the antiarrhythmic action. We investigated the hypotensive effect of rilmenidine, a sele ctive IR agonist (1, 3, and 10 mu g/kg i.v.), and the antiarrhythmic e ffects of the drug on epinephrine-induced arrhythmias during halothane anesthesia in dogs. Although the hypotensive effect of rilmenidine wa s not remarkable in the dose range we tested, rilmenidine increased th e arrhythmogenic threshold for epinephrine in a dose-dependent manner during halothane anesthesia, achieving statistical significance at 10 mu g/kg, the highest dose we examined. These results suggest that rilm enidine prevents epinephrine-induced arrhythmias during halothane anes thesia and that this effect is more potent than its hypotensive action .