ANTIFIBRILLATORY EFFECT OF TETRAHYDROBERBERINE

Electric stimulation and drug-induced ventricular fibrillation (VF), m onophasic action potentials (MAP), and triggered activity were studied before and after administration of tetrahydroberberine (THB) in rabbi ts, rats or guinea pigs. At doses of 5, 10, and 20 mg.kg-1, iv THB inc reased the ventricular fibrillation threshold, and the BaCl2-induced V F was also prevented or terminated by THB in rabbits. Centrogenic VF i nduced by icv aconitine in rats was inhibited by pretreatment with THB in a dose-dependent manner, whereas VF induced by iv ouabain in guine a pig was inhibited to a lesser degree. For MAP, the duration at 90% r epolarization (MAPD90) was prolonged remarkably, whereas the MAPD20, t he MAP amplitude, and the maximal velocity of phase 0 were shortened o r decreased slightly. The amplitudes of early afterdepolarization prod uced by cesium chloride (CsCl) were attenuated, while the cumulative t hreshold doses of CsCl for sustained ventricular tachycardia were elev ated by THB. These results indicated that THB had an potent antifibril latory effect, which might be attributed to its blockade of potassium, calcium, and sodium currents.