RESUMEN
The effect was investigated of administering ground Senna occidentalis seeds to rabbits in different concentrations (1%, 2%, 3% and 4%) in the ration. The experiment lasted 30 days and the toxic effects of the plant were evaluated on the basis of weight gain, histopathological, biochemical and morphometric parameters, as well as histochemistry and electron microscopy. Animals that received the ration containing 4% ground S. occidentalis seeds gained less weight (p < 0.05) and died in the third week. Histopathology revealed that the heart and liver were the main organs affected, with myocardial necrosis and centrolobular degeneration. There was a reduction in cytochrome oxidase activity in the glycogenolytic fibres, together with muscle atrophy, confirmed by the morphometric studies. Electron microscopy of the liver cells revealed dilated mitochondria, with destruction of the internal cristae.