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 spa smogens. Although it nonspecifically antagonized guinea pig ileum contracti ons induced by 7 different spasmogens, it had no effect on depolarization-i nduced contractions of rat aorta or those induced by acetylcholine, histami ne or serotonin in the guinea-pig trachea. Spontaneous rhythmic contraction s of rat portal veins were also not affected by the extract. Serotonin-incl uced contractions of rat aorta were most effectively inhibited by the agent . The observed effects of the extract were more prominent after it was wash ed out of the organ bath. Surprisingly, however, the extract also exerted n egative inotropic and chronotropic effects on the rat atrium preparation. O ur observations revealed several pharmacological properties of the Hypericu m extract, and thus could be helpful in identifying and characterizing its active components and their modes of action.