Cardiovascular responses to acute myocardial ischaemia in morphine-dependent rats.
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 tail-immersion 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did not occur in animals receiving morphine for 2 weeks and in a 3 week morphine-treated group which was subsequently withdrawn for 2 weeks. 5.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.
Ko
W W
WW
Department of Pharmacology, Faculty of Medicine, University of Hong Kong.
Dai
S
S
Chan
M Y
MY
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D001835:Body Weight / Q000187:drug effects; D003327:Coronary Disease / Q000503:physiopathology*; D003331:Coronary Vessels / Q000502:physiology; D004361:Drug Tolerance; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects*; D008297:Male; D009020:Morphine / Q000494:pharmacology; D009021:Morphine Dependence / Q000503:physiopathology*; D009270:Naloxone / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013375:Substance Withdrawal Syndrome / Q000503:physiopathology; D013610:Tachycardia / Q000503:physiopathology; D014693:Ventricular Fibrillation / Q000503:physiopathology
D009270:Naloxone; D009020:Morphine