ABSTRACT
The methanol extract of fresh leaves of Solanum melongena L. (Solanaceae) was evaluated for its capacity to alter the tone of isolated, pre-contracted guinea pig tracheal chains, as well as for its possible mechanism(s) of action. Using serial dilutions between 0.0025 and 2.5 mg/mL, the extract was found to cause a dose-dependent increase in the force of muscle contraction. The EC(50) value was 0.46 +/- 0.01 mg/mL. The concomitant use of acetylcholine 10(-5) M did not significantly affect the force of contraction induced by the extract. Histamine 10(-5) M added at about 40% to, and salbutamol 10(-6) M antagonized by about 30% its constrictive effect. Chlorpheniramine 10(-6) M, propanolol 10(-5) M, and nifedipine 10(-6) M did not significantly influence the extract-induced force of contraction, but atropine 3 x 10(-7) M reduced it by approximately 60%. These data suggest that the Solanum melongena extract exerted a bronchospasmogenic rather than a bronchospasmolytic effect, probably through muscarinic receptor stimulation.