Cardioactive effects of hornet venom, Vespa mandarinia

In the experiment of electrocardiogram, the crude venom of giant hornet (Vespa mandarinia) showed cardioactive effects on rat heart. The heart rate was accelerated within 5 min after injection of the venom intraperitoneally, then the heart beat was blocked, resulting in conduction delay. The cardioactive constituent was separated into two components by gel filtration. One which was high molecular species such as protein showed complete atrioventricular block. Another component, having a low molecular weight, was fractionated in 5 peaks, which accelerated heart rate.