Relaxant effect ofCuminum cyminumon guinea pig tracheal chains and its possible mechanism(s)

OBJECTIVE: To examine the relaxant effects of the macerated and aqueous extracts of Cuminum cyminum on the tracheal chains of guinea pig. MATERIALS AND METHODS: The relaxant effects of cumulative concentrations of macerated and aqueous extracts (0.25, 0.5, 0.75 and 1.0 g%) in comparison with saline and theophylline (0.25, 0.5, 0.75, and 1.0 mM) were examined on pre-contracted tracheal chains of guinea pigs under different conditions. RESULTS: In Group 1 experiments (contracted by KCl) only the last two concentrations of theophylline and the highest concentration of macerated extract showed significant relaxant effect compared to that of saline (P<0.001 and P<0.05 for theophylline and macerated extract respectively). The effects of the last two concentrations of theophylline in this group were significantly greater than those of the macerated and aqueous extracts (P<0.001). However, in Group 2 experiments (contracted by methacholine) both the extracts and theophylline showed concentration-dependent relaxant effect compared to that of saline (P<0.05 to P<0.001). The effects of the two last concentrations of both extracts were significantly lower than those of theophylline in Group 2 experiments (P<0.05 to P<0.001). In Group 3 (non-incubated, contracted by methacholine) the extracts of Cuminum cyminum did not show any relaxant effect of tracheal chains. The relaxant effects of macerated and aqueous extracts in Groups 1 and 3 were significantly lower than those of Group 2 (P<0.05 to P<0.001). However, the effects of different concentrations of theophylline obtained in Group 1 and 2 were not significantly different. There was a significant correlation between the effects and concentrations of theophylline in Groups 1 and 2, macerated extract in Groups 2 and 3 and aqueous extract in Group 1 (P<0.05 to P<0.001). CONCLUSION: These results show a potent relaxant effect of Cuminum cyminum on guinea pig tracheal chains which may be due to a stimulatory effect of the plant on β-adrenoceptors and/or an inhibitory effect on histamine H1 receptors.