MECHANISM OF EPINEPHRINE-INDUCED DYSRHYTHMIAS IN RAT INVOLVES LOCAL CHOLINERGIC ACTIVATION

Alterations of autonomic tone can induce cardiac dysrhythmias. In the present experiments intravenous administration of epinephrine (15 mu g /kg) caused dysrhythmias in rat hearts. Bilateral vagotomy or yohimbin e treatment did not suppress the dysrhythmic effects of epinephrine. A tropine, glycopyrrolate, and pertussis toxin reduced the number of pre mature ventricular contractions and eliminated missed beats caused by epinephrine. Neostigmine increased the number of missed beats but did not change the number of premature ventricular contractions. These res ults indicate that epinephrine induces cardiac dysrhythmias in part by local release of acetylcholine. Muscarinic receptors and pertussis to xin sensitive G proteins are involved in epinephrine-induced arrhythmo genesis.