Bronchodilatory and anticholinergic effects of nigella sativa on isolated guinea pig tracheal chains

ABSTRACT

Nigella sativa is a grassy plant which is believed to have several therapeutic effects including anti-asthmatic properties. We have studied the bronchodilatory and anticholinergic effects of this plant. The bronchodilatory effects of aqueous extract [AE], and macerated extract [ME], were compared against 4 theophylline [T] and saline for their relaxant effects on precontracted isolated tracheal chains of guinea pig, which was induced by 10 methacholine [M]. The anticholinergic effects of AE, ME, together with 5 nM atropine [A] were tested by performing the cumulative log concentration-response curves [LCRC] of M-induced contraction of tracheal chains, and comparing the effective concentration of M causing 50% of maximum response [EC50] in the presence of AE, ME, and A compared with saline [n=10 for all experiments] [p<0.001]. The relaxant effect of ME was due to non-competitive antagonism at muscarinic receptors [non-parallel right-ward shifts in LCRCs obtained in the presence of ME compared to that of saline]. However, the relaxant effect of AE was mainly due to a competitive effect at muscarinic receptors [parallel right-ward shifts in LCRCs obtained in the presence of AE compared to that of saline]. Our results also did not show any anticholinergic behavior of different extracts is probably due to the differences in the methods used, which might lead to the extraction of different substances or the destruction of some substances due to high temperatures