Relaxant effect of ethanol extract of Bacopa monniera on trachea, pulmonary artery and aorta from rabbit and guinea-pig

The relaxant action of an ethanol extract of Bacopa monniera was examined on ring segments of pulmonary arteries (guinea‐pig and rabbit), aorta (rabbit) and tracheal preparations (guinea‐pig). The plant extract induced relaxation in all the tissues in a dose‐dependent manner. Guinea‐pig main pulmonary artery was found to be the most responsive to the plant extract, however, complete relaxation was obtained in the tracheal preparations. The relaxant response to the plant extract was unaffected by pretreatment of the blood vessels with either atropine or propranolol, whereas in the tracheal preparations propranolol partially blocked the response. Indomethacin reduced the plant extract‐induced relaxation in all the tissues. In blood vessels relaxation induced by the plant extract was not modified in the presence or absence of the endothelial layer. These results suggest that relaxation induced by Bacopa monniera possibly involves prostacyclin compounds (in all the tissues) and β‐adrenoceptors (in tracheal preparations). Furthermore, this relaxation is independent of endothelium and muscarinic receptors activation. © 1997 John Wiley & Sons, Ltd.