CARDIOVASCULAR RESPONSES TO ACUTE MYOCARDIAL ISCHAEMIA IN MORPHINE‐DEPENDENT RATS

Publisher Website
Google Scholar
Abstract
SUMMARY: 1. The cardiovascular responses to acute myocardial ischaemia were studied in opiate‐dependent animals before and after 2 weeks morphine withdrawal.2. Rats were treated with morphine sulphate in drinking water for 2, 3 or 5 weeks. The development of morphine tolerance and dependence was verified by the tailimmersion test for analgesia and the naloxone‐precipitated withdrawal syndrome, respectively.3. Acute left coronary artery ligation induced a decrease in blood pressure, a slight increase in heart rate and ventricular tachycardia or fibrillation in anaesthetized naive rats.4. Chronic morphine treatment did not alter the haemodynamic responses to coronary artery ligation. However, a significantly lowered incidence, and prolonged time of onset, of ventricular arrhythmias was found in 3 and 5 week morphine‐treated rats. This phenomenon did not occur in animals receiving morphine for 2 weeks and in a 3 week morphine‐treated group which was subsequently withdrawn for 2 weeks.5. It is suggested that the decreased occurrence of early ventricular arrhythmias resulting from acute myocardial ischaemia in chronic morphine‐treated rats may be related to the degree of opiate tolerance and dependence.