Spasmogenic effect of a Solanummelongena leaf extract on guinea pig tracheal chains and its possible mechanism(s).
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.