Objective: Toluene is a volatile hydrocarbon that is principally used in industry and can cause central and peripheral nervous system impairment. Melatonin, the principal secretory product of the pineal gland, functions as a potent antioxidant and free radical scavenger. This study was designed to investigate the harmful effects of toluene inhalation and protective effects of melatonin in the prefrontal cortex of rats.

Material and Methods: For this purpose, 21 adult male Wistar-albino rats (200-220 g) were randomly divided into three equal groups. Animals in group I were used as control group. The rats in group II were exposed toluene (3000 ppm/1hour/day) for 4 weeks, while the rats in group III treated with melatonin (10 mg/kg/day, ip) plus toluene inhalation. At the end of 4 weeks experimental period, all rats were killed by decapitation. The prefrontal cortex tissues were removed and fixed in % 10 neutral formalin solution. Then tissue specimens were embedded in paraffin and sectioned (thickness, 5μm). The sections were immunohistochemically stained using TUNEL method for determination apoptosis.

Results: Increased numbers of apoptotic cell were observed in the prefrontal cortex of toluene inhaled rats. Treatment of melatonin markedly reduced the the number of apoptotic cells.

Conclusion: In conclusion, in the present immunohistochemical study, we found that melatonin treatment prevents toluene-induced neuronal damage in the prefrontal cortex of rats.