Bronchodilatory and anticholinergic effects of Polygonum avicular on isolated tracheal chains of the guinea pig

  In this study we investigated the bronchodilatory and anticholinergic effects of the aqueous extract (AE), brewed extract (BE) and ethanol extract (EE) of Polygonum avicular in comparison with saline (S) on isolated tracheal chains of the guinea pig. Due to the probable confounding effect of ethanol in the EE, the effects of this extract were also compared with 96 % ethanol. None of the plant extracts showed any relaxant effect compared to S neither did the EE show any significant bronchodilatory effect in comparison with ethanol. On the other hand, there was a clear rightwards shift in the methacoline log concentration-response curves obtained in the presence of AE, BE and EE in comparison with the S curve. This shift was more pronounced in the presence of AE. In the presence of AE, the methacoline EC50 showed a significant difference with that of S. The slope of the methacoline log-response curve obtained in the presence of AE was significantly lower than the S curve (p<0.001), indicating non-competitive antagonism of this solution. The difference between the slope of the methacoline-response curve of other extracts compared to the S curve was not significant, suggesting a mechanism of competitive antagonism for these solutions. In conclusion, these data demonstrate the anticholinergic effect of P. avicular, but do not show the plant extracts to have any relaxant effect. The variation of anticholinergic behaviors among different extracts is probably due to the variety of extracted substances in the different solutions.