Spasmolytic activities of Hydrastis canadensis L. on rat uterus and guinea-pig trachea

This study describes the reversible smooth muscle relaxant activities of an alcoholic extract of Hydrastis canadensis L. on rat uterine preparations and guinea-pig trachea. In the non-pregnant rat uterus the extract inhibited the amplitude of rhythmic spontaneous contractions (IC50 10 +/- 3.07 mu g/mL) and of contractions induced by 5HT (IC50 19.9 +/- 3.87 mu g/mL), oxytocin (IC50 10.5 +/- 0.37 mu g/mL) and acetylcholine (IC50 9.95 +/- 1.77 mu g/mL). The extract also relaxed carbachol precontracted guinea-pig trachea (EC50 1.6 +/- 0.943 mu g/mL). Timolol partially antagonized this effect on trachea strips (EC50 5.28 +/- 0.653 mu g/ mt) suggesting that the extract produces relaxation by beta-adrenoceptor-dependent and -independent mechanisms.