MECHANISM OF ACTION OF THE AQUEOUS SEED EXTRACT OF MUCUNA-PRURIENS ONTHE GUINEA-PIG ILEUM

The hot water extract (HWE) of the seed of Mucuna pruriens dose-depend ently contracted the guinea-pig ileum. The ED50 and pD(2) values for t he HWE was lower than those of ACh and histamine, Cyproheptadine and p romethazine (10 ng/mL) significantly antagonized the effects of histam ine, 5-hydroxytryptamine (5-HT) and HWE. Atropine blocked the effect o f ACh and partially blocked the HWE. The calcium channel blockers nife dipine and verapamil both blocked the effects of all the agonists incl uding HWE. These results suggest that the HWE contains potent histamin e receptor stimulants or principles as it was blocked by low doses of H-1 receptor blockers. It appears that stimulation of the receptors le ads to influx of calcium since the effect was also blocked by nifedipi ne and verapamil. It is likely that it also stimulates muscarinic rece ptors. (C) 1997 by John Wiley & Sons, Ltd.