Myocardial Dysfunction and Pathology Associated with Environmental Stress in Squirrel Monkey: Effect of Vagotomy and Propranolol

The influence of autonomic innervation on stress-induced cardiomyopathy and heart rate changes was analyzed by selective removal of parasympathetic and sympathetic myocardial inputs. Squirrel monkeys with bilateral cervical vagotomy or β-adrenergic receptors blocked by propranolol were studied in shock stress and restraint situations. Because propranolol reduced stress-induced lesions and tachycardia, enhanced sympathetic β-receptor activity was considered responsible for these effects in intact monkeys. No role for increased parasympathetic activity in myocardial pathology was indicated. Enhanced sympathetic activity was also implicated by lesions and tachycardia of vagotomy monkeys. However, vagotomy alone induced myocardial pathology and confounded the effects of shock stress. Stress-induced cardiac arrest in both vagotomy and propranolol monkeys was observed. An imbalance of either autonomic input was suggested to be responsible for this dysfunction. Thus, autonomic innervation was involved in stress-induced cardiomyopathy and heart rate changes.