Oriental hornet venom: effects on cardiovascular dynamics

The hemodynamic effects of the intravenous injection of dry venom of Vespa orientalis were studied in ten dogs. Heart rate, aortic and right ventricular pressure, the first derivative of the right ventricular pressure, the cardiac output and the peripheral vascular resistance were determined. The venom acted within 10 sec and its effects lasted for several minutes. Respiration increased, mean aortic pressure and peripheral vascular resistance fell while cardiac output was increased by 60 per cent. High doses produced arrhythmias, shock and death. Vagotomy and atropine administered prior to the venom administration diminished the respiratory excitation, but had no effect upon cardiac pressures and output. Blockade of 5-hydroxytryptamine, one of the components of the venom, prevented most of the venom action except for vasodilation. Beta-blockade had a lesser effect upon the venom activity. While most of the Oriental hornet venom activity can be explained by the presence of biogenic amines active upon the cardiovascular system, a potent unidentified vasodilator material with possible positive inotropic properties exists in the venom.