Author : Mohammed Ali, Ihsan Husain
Iraqi Journal of Veterinary Sciences,
This study aims to investigate the mechanism(s) included in the bronchodilation effect exerted by Nigella sativa. Ethyl acetate extract (NS.EA) was prepared using a maceration method. Adult albino rats were recruited for thoracotomy and removal of the trachea. After cutting into pieces, the tissue was set in organ bath. The influence of cumulative concentrations of ethyl acetate extract was examined on contractile responses of isolated trachea to acetylcholine using different blockers such as Nifedipine (Ca2+channel blocker), Tetraethylammonium (Ca2+-activated K+ channel blocker), 4-aminopyridine (voltage-dependent K+ channel blocker), Glibenclamide (ATP-sensitive K+ channel blocker), BaCl2 (inward rectifier K+ channel blocker), methylene blue (soluble gaunylate cyclase inhibitor) and indomethacin (non-selective cyclooxygenase inhibitor). Significant inhibition of bronchodilation was observed when tracheal rings were pretreated with indomethacin and BaCl2 with (P<0.001), and with methylene blue and nifedipine with (P<0.05). The IC50s were (5.635, 6.9, 7.86 and 4.987 mg/ml) respectively. Conversely, 4-AP, GLIB and TEA showed no significant changes in the bronchodilation induced by the extract. Therefore, The Emax value for indomethacin significantly reduced from 101.34 to 73.28%, BaCl2 from 53.62 to 30.31%, methylene blue from 55.78 to 38.94% and nifedipine from 101.34 to 80.88%. On the other hand, the Emax for 4-AP and GLIB were non-significantly reduced from 53.62 to 40.14 and 40.13% respectively; and TEA more or less unchanged to 54.34%. In general, ethyl acetate extract of N. sativa induces bronchodilation through four mechanisms (activation of Kir channel, non-selective cyclooxygenase and to lesser extent the soluble guanylate cyclase, and blockade of Ca2+ channel).