Receptor mechanisms for clonidine reversal of bupivacaine-induced impairment of ventricular conduction in pentobarbital-anesthetized dogs

Possible mechanisms of the ability of clonidine to correct bupivacaine-induced ventricular electrophysiologic impairment were evaluated in an electrophysiologic model on closed-chest dogs. Nine groups (n=6) of pentobarbital-anesthetized dogs were given atropine, 0.2 mg/kg intravenously (IV), and bupivacaine, 4 mg/kg IV, over a 10-s period. Group 1 was then given only saline solution. Group 2 was given clonidine, 0.01 mg/kg IV, over a 1-min period. Group 3 was given clonidine followed by IV administration of yohimbine, 1 mg/kg, an α 2 -antagonist. Group 4 was given carbachol, 1 mg/kg IV, a long-lasting cholinergic agonist, over a 1-min period. Group 5 was given electrical stimulation of the left vagus nerve