THE INTERACTIONS OF PAEONIFLORIN AND VERATRINE ON ISOLATED RAT ATRIA

In this study, we attemped to identify the interactions and mechanisms between veratrine and paeoniflorin on isolated rat atria. Paeoniflori n alone showed no effect on the rat atria. Veratrine increased the atr ial contraction and induced arrhythmia at 1 x 10(-5) g/ml. Veratrine c ould directly induce contraction and elicit tetanic contraction at 1 x 10(-4) g/ml in the left atria with or without electric stimulation. P aeoniflorin (4.8 x 10(-6) to 4.8 x 10(-3) g/ml), verapamil (2.2 x 10(- 6) g/ml), tetrodotoxin (TTX) (3.2 x 10(-8) g/ml) and quinidine (7.5 x 10(-6) g/ml) inhibited the increase of contraction and delayed the ons et of contraction induced by veratrine (1 x 10(-5) g/ml). The inhibito ry effect of paeoniflorin combined with verapamil on the contraction i nduced by veratrine was more potent than that of paeoniflorin or verap amil alone, However, the inhibitory effect of paeoniflorin was not pot entiated by TTX or quinidine. From the above results, the contraction evoked by veratrine in the rat atria may be concluded to be caused by the stimulation of Na+- and Ca2+-ion channels. The inhibition of paeon iflorin on the contraction induced by veratrine may primarily be relat ed to the blockade of Ca2+ channels. (C) 1997 Elsevier Science Ireland Ltd.