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Malathion is an organophosphate widely used as an insecticide in agriculture and in public health programs, causing risk to human health. As was recently reported, malathion induces depressant-like behavior and oxidative damage to the brain of rodents. Given the relevance of searching for neuroprotective agents against such damage, this study was therefore undertaken to investigate the neuroprotective potential of zinc in dealing with malathion-related toxicity. Female Wistar rats were exposed to malathion (50 and 100 mg/kg, ip) and/or zinc chloride (ZnCl2; 5 mg/kg, ip) for 3 days. Malathion produced a depressant-like effect, observed by the increased immobility time in the forced swimming test (FST), without affecting total locomotor activity and rearing in the open-field. However, malathion administered at 50 mg/kg reduced the central time in the arena and at the dose of 100 mg/kg reduced the central locomotion. These effects were completely reversed by ZnCl2. Exposure to malathion (50 mg/kg, ip) and/or ZnCl2 did not affect AChE activity in the hippocampus, cerebral cortex, and blood. Malathion (50 mg/kg, ip) alone caused some harmful effects, such as (1) an increase in lipid peroxidation and a reduction of glutathione peroxidase activity in the cerebral cortex, (2) reduction of glutathione reductase activity in the hippocampus, and (3) changes in the structure of chromatin in the dentate gyrus, all effects attenuated by ZnCl2. In conclusion, these results clearly show that zinc administration is able to attenuate some neurochemical, morphological, and behavioral effects induced by malathion, notably the malathion-induced depressant-like effect in the FST.

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RESUMO:Solidago chilensis Meyen (Asteraceae) é uma espécie nativa da América do Sul (Brasil) encontrada principalmente na região Sul do Brasil onde é conhecida popularmente como arnica-do-mato. Na medicina popular, ela é utilizada como diurética, cicatrizante, e antiinflamatória. No presente trabalho, os efeitos farmacológicos do extrato aquoso das raízes de S. chilensis foram avaliados em modelos experimentais in vivo de atividade tipo-antidepressiva, antiinflamatória, antinociceptiva, e locomotora. O extrato (25, 100 e 250 mg kg -1 ) foi administrado por via oral 30 min antes dos experimentos comportamentais. Os resultados mostram que, nas doses utilizadas, o extrato aquoso de S. chilensis não apresentou atividade tipo-antidepressiva apesar de induzir efeitos analgésico e antiinflamatório significativos. Uma redução da atividade locomotora foi observada com a maior dose (250 mg kg -1 ) administrada, sugerindo efeito sobre o sistema nervoso central. Em conclusão, os resultados estão de acordo com a literatura acerca dos efeitos analgésicos e antiinflamatórios da planta, sugerindo também uma atividade do extrato de S. chilensis sobre o sistema nervoso central. Essas observações, porém, não excluem um possível efeito relaxante muscular periférico do extrato. Palavras-chave: Solidago chilensis, analgesia, inflamação, depressão, atividade farmacológicaABSTRACT: Pharmacological effect of aqueous extract from Solidago chilensis Meyen on mice. Solidago chilensis Meyen (Asteraceae) is a species native to South America (Brazil), found especially in the south region of Brazil, where it is commonly known as "arnica-do-mato". In folk medicine, it has been used as diuretic, healing and anti-inûammatory. In the present study, the pharmacological effects of aqueous extracts from roots of S. chilensis were assessed in vivo in experimental models for antidepressant, anti-inflammatory and locomotor-type activity. The extract (25, 50 and 250 mg kg ) was administered by the oral route 30 minutes prior to behavioral tests. Results indicate that, at the employed levels, aqueous extract from S. chilensis did not show antidepressant-type activity although it induced significant analgesic and anti-inflammatory effects. A reduction in the locomotor activity was noted at the highest administered level (250 mg kg -1 ), suggesting an effect on the central nervous system. In conclusion, results agree with the literature about analgesic and anti-inflammatory effects of this plant, also suggesting an activity of S. chilensis extract on the central nervous system. These remarks, however, do not exclude a possible peripheral muscular relaxing effect of the extract.

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