Abstract
1. The effects of buprenorphine, given intravenously, on the incidence and severity of early acute coronary artery occlusion-induced arrhythmias were examined in anaesthetised rats. The electrophysiological effects of buprenorphine were also examined in sheep Purkinje fibres and rat papillary muscles, superfused in vitro with either a normal or a hypoxic, hyperkalaemic and acidotic physiological salt solution (PSS). 2. In anaesthetised rats subjected to acute coronary artery occlusion, pretreatment with buprenorphine (1 mg kg-1 i.v.) markedly reduced the incidence of ventricular extra-systoles during the initial 30 min post-occlusion period. The incidence of ventricular fibrillation (VF) was also significantly reduced from 56% to 10%. 3. At the antiarrhythmic dose (1 mg kg -1), buprenorphine also attenuated the sudden fall in systemic arterial blood pressure induced by acute coronary artery ligation. 4. In normal sheep Purkinje fibres and rat papillary muscles, buprenorphine (10(-6)-10(-5) M) significantly reduced the action potential height and maximum rate of depolarisation of phase zero (MRD) and prolonged the duration of the action potential. 5. Superfusion of sheep Purkinje fibres and rat papillary muscles with a hypoxic, hyperkalaemic and acidotic PSS resulted in marked reductions in resting membrane potential, upstroke and duration of the action potential. 6. In the presence of the modified compared with normal PSS, buprenorphine reduced the action potential height and MRD of both sheep Purkinje fibres and rat papillary muscles to a greater extent, although its ability to prolong the action potential duration was attenuated. 7. The antiarrhythmic effects of buprenorphine observed in vivo may be explained by its direct cardiac electrophysiological effects. Buprenorphine might be useful in relieving pain and in reducing the severity of arrhythmias in the early stages of acute myocardial infarction.