RESUMO
BACKGROUND: In previous studies, the bronchodilator and antitussive effects of Nigella sativa have been demonstrated on guinea pigs. OBJECTIVES: In the present study, the effect of the hydroethanolic extract of N. sativa on tracheal responsiveness in guinea pigs exposed to cigarette smoke was examined. MATERIALS AND METHODS: Three groups of guinea pig models of COPD were given drinking water alone (COPD group), drinking water containing vitamin C (COPD + VC group), and N. sativa (COPD + NS group). Tracheal responses to methacholine were measured as effective concentration causing 50% of maximum response (EC50 M) in control animals (group C) and three groups of guinea pigs with COPD (n = 7, for all groups). Tracheal responses to 0.1% ovalbumin in comparison to contraction obtained by 10 µM methacholine were also examined. RESULTS: The tracheal responsiveness to both methacholine and ovalbumin in guinea pigs with COPD were significantly higher than those of controls (P < 0.001 for both cases). The tracheal responsiveness in the COPD + VC and the COPD + NS groups to both methacholine and ovalbumin were significantly decreased in comparison to the COPD group (P < 0.05 and P < 0.001, respectively). CONCLUSIONS: These results showed the preventive effect of hydroethanolic extract of N. sativa on tracheal responsiveness of guinea pig model of COPD, which was as effective as vitamin C.