INFLUENCE OF CENTRAL AND INTRAVENOUS ADMINISTRATION OF DRUGS ON CARDIAC-ARRHYTHMIAS INDUCED BY PERIPHERAL MECHANISMS IN ANESTHETIZED RATS

The intrajugular injection of isoprenaline, epinephrine, or calcium ch loride (CaCl2) induced reversible cardiac arrhythmias in urethane-anes thetized rats, Most of these arrhythmias could be prevented by acebuto lol, propranolol, atropine, cimetidine, or muscimol administered in th e lateral cerebral ventricle, However, CaCl2-induced arrhythmias were not influenced by these drugs, Thus it may be concluded that in cardia c arrhythmias induced by the stimulation of cardiac beta-adrenergic re ceptors, there is a permanent central modulation of cardiac excitabili ty.