The calcium antagonist action of arctigenin (ACT) was studied in order to verify the effect of Fructus Arctii for the relieve
of exterior syndrome Muscular
contraction of isolated rat trachea, colon, pulmonary artery and thoracic aorta induced by KCl, that of guinea pig trachea induced by CaCl 2, before and after the addition of ACT were assessed and their contraction response curves drawn and PD'2 calculated according to Scott The inhibition rate of two phase contraction of guinea pig trachea induced by acetylcholine chloride (Ach) in comparison with verapamil (VER) was calculated Results of the study showed that ACT could non compatitively antagonize the muscular contraction of the test specimens with PD' 2 of 4 01, 5 11, 5 98 and 6 05
respectively Similar to VER, ACT could non competitively antagonize the isolated guinea pig trachea with PD'2 of 4 04 and 5 62 respectively Both of them could inhibit the first phase contraction induced by Ach with inhibition rates of 66 14% and 81 42% respectively It was concluded that ACT, as the active constituent of Fructus Arctii, relaxed smooth muscle contraction by blocking the potential dependant Ca 2+ channel and the internal release of Ca 2+