A 5-HT₆R agonist alleviates cognitive dysfunction after traumatic brain injury in rats by increasing BDNF expression

Effective treatment for cognitive dysfunction after traumatic brain injury (TBI) is lacking in clinical practice. Increased brain-derived neurotrophic factor (BDNF) expression in cognitive circuits can significantly alleviate cognitive dysfunction in animal models of TBI. Selective 5-hydroxytryptamine receptor 6 (5-HT₆R) agonists significantly increase BDNF expression and improve cognitive function. Therefore, we evaluated the protective effect of a highly selective 5-HT₆R agonist, WAY-181187, on cognitive dysfunction after TBI. We established a controlled cortical impact model of moderate TBI in rats and performed drug intervention for five consecutive days. Rats had spatial reference memory impairment in the Morris water maze one and four weeks after TBI. BDNF expression in the medial prefrontal cortex (mPFC) and hippocampus decreased two and five weeks after TBI. Additionally, five weeks after TBI, decreases in neuronal dendritic spine density and the proportion of thin, mushroom-shaped dendritic spines and an increased proportion of stubby-type dendritic spines were observed. WAY-181187 administration (3 mg/kg) for five consecutive days after TBI significantly alleviated cognitive dysfunction at one and four weeks (P < 0.001 and P < 0.01), upregulated BDNF expression in the mPFC and hippocampus at two (P < 0.01 and P < 0.05) and five (P < 0.01 and P < 0.001) weeks and increased the dendritic spine density and the proportions of thin, mushroom-shaped dendrites in the mPFC (P < 0.05, P < 0.001 and P < 0.01) and hippocampus (P < 0.05, P < 0.001 and P < 0.05) at five weeks after TBI. Our results confirm that WAY-181187 administration (3 mg/kg) in the acute phase alleviated cognitive dysfunction after TBI, possibly by upregulating BDNF expression in the mPFC and hippocampus, enhancing neuroplasticity.