Cardiac Output and Blood Flow Distribution during Rest and Classical Aversive Conditioning in Monkey

Abstract

ABSTRACT Cardiac output was measured by dye dilution in rhesus monkeys (n = 9) during rest and classical aversive conditioning. A 1‐ min tone (followed by unavoidable electric shock) served as the conditional stimulus (CS +). Cardiac output was determined at approximately 30 sec before and after onset of CS +. Conditional increases in mean blood pressure (78± 11 to 84±11 mmHg. average±SD) and heart rate (145±23 to 166 ± 31/min) were associated with a significant (p<.01) increase in cardiac output (1.32 ± .25 to 1.69±.51 L/min) and decrease in total peripheral resistance (60.8 ± 13.7 to 53.1 ± 14.8 mmHg/L/min). There were no significant changes in these variables during a different tone (CS‐) which was never followed by shock. Infusion of radio‐labeled microspheres (5 monkeys) at 25‐30 sec after CS + onset revealed a conditional increase (vs resting control) in flow to the diaphragm and certain other skeletal muscle; myocardial blood flow was not increased at this time. Flow decreased to the kidney, liver and pancreas. Elimination of the conditional increase in blood How to skeletal muscle following administration of propranolol (3 monkeys) suggests that the redistribution of cardiac output during “stress” may involve an active adrenergic vasodilation in the non‐human primate.