Possible mechnisms of relaxant effect of Portulaca oleraceae on tracheal chains of guinea pig

Therapeutic effect of Portulaca oleraceae on respiratory diseases is indicated in Iranian ancient medical books. The relaxant effect of this plant also observed on smooth muscles in previous studies. Therefore, in the present study, the possible mechanism (s) for the relaxant effects of boiled and aqueous extracts of Portulaca oleraceae on tracheal chains of guinea pigs were examined. The relaxant effects of 5 volumes of boiled (0.25, 0.5, 0.75, 1.0, and 1.25 ml of 5% W/V) and aqueous (0.125, 0.25, 0.375, 0.5, and 0.625 ml of 10%W/V) extracts were examined by their relaxant effects on pre-contracted tracheal chains of guinea pigs by 1 10 µM methacholine on: 1) non incubated tissues, and 2) incubated tissues with propranolol and chlorpheniramine in comparison with the effects of saline, theophylline, (n=6 for both groups). In groups 1 and 2 experiments both boiled and aqueous extracts and theophylline showed concentration dependent relaxant effect compared to that of saline (p