title: Increased incidence of isoproterenol-induced ventricular fibrillation in aging rats.
abstract: Prolonged beta-adrenergic stimulation obtained by subcutaneous injection of isoproterenol in unanesthetized, unrestrained rats elicited ventricular fibrillation in approximately 80% of animals at 10-12 months of age. Ventricular fibrillation failed to occur in 1-month-old rats and involved only 12% of rats at 2 months. Senescence appeared not to increase the frequency of ventricular fibrillation since a similar incidence was seen in rats at 10-12 and 19-21 months. In all instances, ventricular fibrillation was preceded by ECG changes consistent with acute subendocardial ischemia. To evaluate whether acute beta-adrenergic stimulation elicits comparable cardiovascular effects in animals of different age, a dose-response curve to intravenous injection of isoproterenol was performed in anesthetized rats. Changes in heart rate, systemic arterial pressure, left ventricular pressure, and dP/dt were not different among animal groups. It was concluded that the arrhythmogenic potential of isoproterenol may not be related to differences in cardiac beta-receptor sensitivity with age as suggested by the comparable changes in the inotropic and chronotropic actions of isoproterenol in the animal groups studied.
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D004562:Electrocardiography; D006339:Heart Rate / Q000187:drug effects; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D051381:Rats; D011943:Receptors, Adrenergic, beta / Q000502:physiology; D014693:Ventricular Fibrillation / Q000139:chemically induced*
chemical_list: D011943:Receptors, Adrenergic, beta; D007545:Isoproterenol