ABSTRACT
Aim To observe the effects of Breviscapine (Bre) on the contractions induced by noradrenaline (NA) and high potassium in rabbit aorta strips and to investigate the relationships of these effects to the changes of intracellular free calcium( i). Methods The effects of Bre on the concentration-response curves for NA and high potassium, and on the transient contractions induced by NA and caffeine in Ca 2+-free medium and the sustained contraction by NA after replenishing Ca 2+ were surveyed using rabbit aorta strips; the changes of i increased by NA and high potassium in the presence of Bre were determined using fura-2/AM loaded cultured smooth muscle cells of rabbit aorta. Results Bre shifted the concentration-response curve for NA to right in a dose-dependent manner , but shifted that for high potassium to left; it inhibited the transient contraction induced by NA and caffeine in the Ca 2+-free medium and the sustained contraction induced by NA after replenishing Ca 2+; Bre inhibited the i increased by NA, but enhanced that increased by high potassium in the smooth muscle cells of rabbit aorta. Conclusion Bre inhibits the contraction induced by NA through its inhibition effects on Ca 2+-influx and Ca 2+-release ; it enhances the Ca 2+-influx induced by high potassium, but the mechanism by which Bre enhances the high potassium inducing Ca 2+ -influx is not known.