Lippia alba, Melissa officinalis and Cymbopogon citratus: effects of the aqueous extracts on the isolated hearts of rats.

1. This research was developed to evaluate the actions of the aqueous extracts of leaves of Lippia alba, Melissa officinalis and Cymbopogon citratus upon contractile force (CF) and cardiac rate (CR). 2. For the experiments in isolated heart, 21 male adult rats were used. The hearts were perfused according to Langendorff's method. The records of CF and CR were obtained in control and after application of the extracts. The extracts were utilized in doses: 0.038, 0.38, 3.8 and 38 mg. Results obtained were compared by statistic analyses. 3. The aqueous extracts provoked significant CR reduction and did not alter the CF. The negative CR effect may have occurred by cardiac muscarinics receptors stimulation.