Comparison of the effects of an alcoholic St. John's wort extract on various isolated organs

We have studied the effects of a St. John's wort extract used in therapy on contractions of various isolated organ preparations induced by diverse spasmogens. Although it nonspecifically antagonized guinea pig ileum contractions induced by 7 different spasmogens, it had no effect on depolarization-induced contractions of rat aorta or those induced by acetylcholine, histamine or serotonin in the guinea-pig trachea. Spontaneous rhythmic contractions of rat portal veins were also not affected by the extract. Serotonin-induced contractions of rat aorta were most effectively inhibited by the agent. The observed effects of the extract were more prominent after it was washed out of the organ bath. Surprisingly, however, the extract also exerted negative inotropic and chronotropic effects on the rat atrium preparation. Our observations revealed several pharmacological properties of the Hypericum extract, and thus could be helpful in identifying and characterizing its active components and their modes of action.