Reperfusion arrhythmias in closed-chest rats: the effect of myocardial noradrenaline depletion and Ca2(+)-antagonism

1. The influence of myocardial noradrenaline depletion on the incidence and severity of reperfusion arrhythmias in closed-chest anaesthetized rats was investigated. Five-minute left coronary artery occlusion was carried out via an implanted occluder. Four groups of rats were studied: controls, rats treated with reserpine (5 mg/kg, intraperitoneally) 24 h before occlusion, and rats receiving 0.2 mg/kg gallopamil intravenously 5 min before occlusion either with or without reserpine pretreatment. 2. In the control group all Animals had ventricular tachycardia (VT) and fibrillation (VF) immediately after reperfusion. Gallopamil reduced VT to 50% and VF to 25% (P less than 0.05 versus control). In the reserpine group all had VT, and 67% had VF, this being not significantly different from controls. Additional treatment with gallopamil markedly reduced VT and totally prevented VF (P less than 0.05 versus control). 3. Thus, total depletion of myocardial noradrenaline stores neither prevented the occurrence nor reduced the severity of reperfusion arrhythmia in rats, while gallopamil treatment was effective.