RESUMO
Ethanolic extract of fresh leaves of M. koenigii (MKEE) showed a dose dependent positive inotropic effect on isolated frog heart. The responses to MKEE (62.5-1000 microg) were not affected in either way by theophylline, imidazole, propranolol and sildenafil. The change in potassium and sodium concentration did not alter MKEE-induced positive inotropic effect. Lignocaine did not alter the responses to MKEE significantly. Responses to MKEE were significantly inhibited when calcium concentration was reduced to half (from 1.58 to 0.79 mM) and were significantly potentiated when calcium concentration was doubled (from 1.58 to 3.16 mM). Verapamil was found to inhibit the responses significantly. The results suggest that M. koenigii induced positive inotropic effect possibly by increasing availability of calcium from extra cellular sites.