Chronic sub lethal nerve agent (Soman) exposure induced long-term neurobehavioral, histological, and biochemical alterations in rats

Organophosphorus (OP) pesticides and insecticides are used in agriculture and other industries can also cause adverse effects through environmental exposures in the people working in agricultural and pesticide industries. OP nerve agent exposures have been associated with delayed neurotoxic effects including sleep disorders, cognitive malfunctions, and brain damage in Gulf War victims, and Japanese victims of terrorist attacks with nerve agents. However, the mechanisms behind such prolonged adverse effects after chronic OP nerve agent’s exposures in survivors are not well understood. In the present study, male Wistar rats were subcutaneously exposed to nerve agent soman (0.25XLD₅₀) for 21 consecutive days to evaluate the neurobehavioral, neuropathological and biochemical alterations (oxidative stress and antioxidants levels). Neurobehavioral studies using Elevated Plus Maze (EPM), T-Maze, and rotarod tests revealed that chronic soman exposure produced alterations in behavioral functions including increased anxiety and reduction in working memory and neuromuscular strength. Biochemical studies showed that antioxidants enzyme (glutathione peroxidase (GPx), catalase (CAT), and superoxide dismutase (SOD) levels were reduced and oxidative stress (reduced glutathione (GSH) and lipid peroxidation levels (malondialdehyde (MDA)) were significantly increased in brain at 30 days in soman exposed rats as compared to control rats. Neuroselective fluorojade-c stain was used to examine the brain damage after chronic soman exposure. Results demonstrated that chronic soman exposure induced neurodegeneration as brain damage was detected at 30- and 90-days post exposure. The present study results suggest that chronic nerve agent exposures even at low doses may produce long-term adverse effects like neurobehavioral deficits in rats.