Abstract: Aim To study effect s of rhomotoxin (Rh)on electrophysiologic parameters in rabbit heart.Methods The rabbi t heart s in vivo were injected with Rh 12.5μg·kg^-1,25μg·kg^{- 1} or saline iv respectively and the isolated rabbit hearts were perfused by Krebs-Henseleit(K-H)perfusion liquid containing Rh 0.34 μmol·L^-1 or 0.68μmol·L^-1.The electrophysiologic parameters were observed before and after drug adminitration.Results At 20, 40, 60 and 80 min after inject ion of Rh 12.5μg·kg^-1 iv, the VDT,ERP and RRP had no significant changes ;but at 20, 40, 60 and 80 min after inject ion of Rh 25 μg ·kg^-1 iv a significant prolongation of ERP and (or)RRP was found (P<0.05).Perfusion gisolated heart with Rh 0.34 μmol·L^-1 prolonged ARRP and A ERP (P<0.05, P<0.01);while perfusion gisolated heart with Rh 0.68 μmol·L^-1 increased ADT and VDT(P<0.05, P<0.01)and pro longed ARRP, AERP,VRRP and VERP (P<0.05, P<0.01).Conclusion Rh might have an effect of increasing atrial and ventricular diastolic threshold, which prolongates atrial and ventricular refractory period by direct action on rabbits myocardial muscle.

Key words: rhomotoxin(Rh), rabbit, cardioelectrophy siology, isolated perfused heart