Agomelatine attenuates dexamethasone-induced neurotoxicity in rats through the activation of MT1/2 receptors and attenuation of oxidative stress

Abstract

Previous studies showed that agomelatine ameliorates doxorubicin-induced brain injury in rats. Furthermore, it protects neurons against oxidative stress triggered by acute ischemia reperfusion injury. So, this study aimed to investigate the possible neuroprotective effects of agomelatine on dexamethasone-induced neurotoxicity in rats and the underlying mechanisms. Subcutaneous injections of dexamethasone (10 mg/kg, 4 days) were used to induce neurotoxicity in rats. Agomelatine (10 mg/kg), luzindole (2.5 mg/kg, a melatonin receptor blocker), and luzindole plus agomelatine treatment commenced 3 days before dexamethasone injections and concurrent with dexamethasone injections. Elevated plus maze test, Y-maze test and open field test were carried out after 1 h of the last dose of dexamethasone on day 7. On 8th day of the experiment, brain tissues were collected. Brain oxidative stress markers, immunohistochemical expression of β-amyloid and glial fibrillary acidic protein (GFAP) were measured. Moreover, histopathological changes in the cerebral cortex and hippocampus were recorded and the number of damaged cells was counted. Dexamethasone increased anxiety and memory impairment but decreased locomotor exploration activity. Furthermore, it increased brain oxidative stress, expression of β-amyloid and GFAP, increased the number of damaged neurons, and caused structural changes in cerebral cortex and hippocampus. All these deleterious changes were mitigated by agomelatine. Luzindole prior administration to agomelatine reversed the protective effects of agomelatine except its effect on lipid peroxidation. Collectively, these findings suggest that agomelatine can protect against dexamethasone-induced neurotoxicity partially by activating melatonin receptors in addition to exerting antioxidant effects.