XANTHONOLOL - A CALCIUM-CHANNEL AND BETA-ADRENOCEPTOR BLOCKER WITH VASODILATING PROPERTIES

1. Xanthonolol (0. 1-5.0 mg/kg, i.v.) reduced the blood pressure, hear t rate, and L-isoproterenol (0.05 mug/kg, i.v.)-induced tachycardia in rats. 2. In the isolated guinea-pig right atrium, xanthonolol (10(-6) -3 x 10(-4) M) produced long-lasting negative, inhibited L-isoproteren ol-induced positive chronotropic effects, prevented the rate-increasin g effects of increased extracellular Ca2+ (3.0-9.0 mM), and inhibited Ca2+ (3.0-9.0 mM)-induced heart rate-increase. 3. In the isolated guin ea-pig thoracic aorta, the contractions induced by CaCl2 (0.1-5.0 mM) were inhibited by xanthonolol (10(-6)-10(-4) M). 4. Xanthonolol is sug gested to have a calcium channel and beta adrenergic blocking effect w ith vasodilating properties.