The effects of Heteromorpha trifoliata on gastrointestinal smooth muscle of the guinea pig.

The effects of an aqueous extract of the root bark of H. trifoliata on various smooth muscle preparations were investigated. The extract had no contractile or relaxant effect on guinea pig gastrointestinal smooth muscle (n = 6), trachea (n = 4), taenia coli (n = 6), nor did it affect the spontaneously-beating atrium (n = 5). However, H. trifoliata antagonized ileal contractions induced by acetylcholine, histamine, serotonin (n = 6 for each dose of agonist) and potassium chloride (n = 4) in a concentration-dependent manner. The antagonism was considered to be non-competitive and non-specific in nature. It is concluded that H. trifoliata antagonizes the effects of these various agonists by either preventing calcium influx into the smooth muscle cell, or inhibiting the calcium-induced calcium release mechanism, or preventing the release of calcium from the sarcoplasmic reticulum, or by preventing the binding of calcium to calmodulin. The antagonistic effects exerted by H. trifoliata could explain its rational use in traditional medicine to alleviate abdominal spasms.