Effects of U50488H on ventricular arrhythmias induced by myocardial ischemia and reperfusion in rats

AIM: To investigate the effects of U50488H (a selective к-opioid receptor agonist) on ventricular arrhythmias induced by myocardial ischemia and reperfusion in rats. METHODS: Rats were randomly divided into four groups, i.e., control group, ischemia/reperfusion group (Ⅰ/R), U50488H group and U50488H+Ⅰ/R group respectively. Heart rate (HR), arterial blood pressure (ABP), left ventricular pressure (LVP), contractive function (+dp/dt max ) and diastolic function (-dp/dt max ) were examined in rats. The incidence of ventricular arrhythmias and arrhythmia score were also determined. RESULTS: ① HR, ABP, LVP and ±dp/dt max in rats decreased with the administration of U50488H; ② intravenous injection of U50488H before Ⅰ/R lowered the incidence of ventricular arrhythmias and arrhythmia score (P0.05). The effect of U50488H was abolished in the presence of Nor-BNI, a selective κ-opioid receptor antagonist. CONCLUSION: κ-opioid receptor stimulation by U50488H alters the cardiac rhythm and reduces the occurrence of ventricular arrhythmia induced by myocardial ischemia and reperfusion.