[Vasorelaxant effects of forsythiaside from the fruits of Forsythia suspensa].

The vasorelaxant effects of forsythiaside (compound 1) from the fruits of Forsythia suspensa on isolated rat aortic rings were studied. Compound 1 showed a slow relaxation activity against norepinephrine (NE)-induced contractions of rat aorta with/without endothelium. This compound did not affect contractions induced by a high concentration of potassium (K(+) 60 mM), while it inhibited NE-induced vasocontraction in the presence of nicardipine. These results show that the inhibition by compound 1 of NE-induced vasocontraction is due to a decrease in calcium influx from the extracellular space caused by NE.