RESUMO
This work is an evaluation of possible haemodynamic effects of naloxone. The work was done on isolated perfused heart of rabbit, blood vessels of isolated rat hind limb and anaesthetized dogs. Injection of naloxone in concentration of 1 and 2 ug/ml increased force of myocardial conractility of rabbit's heart, while higher concentration of 4 ug/ml produced arrhythmia. Experiments on perfused blood vessels of isolated rat hind limb demonstrated that naloxone produced no effect on peripheral vascular resistance. While experiments on anaesthetized dogs showed that naloxone in a dose of 10 ug/kg produced significant increase in mean arterial blood pressure [P < 0.05] with no change in heart rate. Injection of naloxone in doses of 20 ug/kg and 40 ug/kg produced different types of ventricular arrhythmias. The increase in blood pressure following naloxone was produced primarily by an improvement in myocardial contractility