OBJECTIVE: This study aims to explore the neuroprotective effects of dexmedetomidine (Dex) in rats suffering from traumatic brain injury (TBI) via the PI3K/Akt/mTOR signaling pathway. METHODS: A weight drop model was performed for TBI model establishment. A total of 150 Sprague Dawley rats were selected and assigned into control, sham, TBI, TBI+Dex, TBI+LY294002 (LY) and TBI+Dex+LY groups. Modified Neurological Severity Score (mNSS) was conducted in order to evaluate the neurological injury. The water content in brain tissues was measured. The expressions of PI3K/Akt/mTOR signaling pathway-related proteins, tight junction proteins (ZO-1 and Claudin-5) and autophagy proteins (LC3 I/II and Beclin-1) were detected using Western blot assay. A TUNEL assay was applied for cell apoptosis, immunofluorescence was employed for the detection of the positive expression of LC3, and ELISA was applied for detection of levels of inflammatory factors [tumor necrosis factor-alph (TNF-a), interleukin-1β (IL-1β), interferon-γ (INF-γ) as well as IL-6], respectively. RESULTS: Compared with the control group, the other four groups exhibited increased mNSS, brain water content, expression of LC3, TNF-a, IL-1β, INF-γ and IL-6, and positive expression of LC3, expression of LC3 I/II and Beclin-1, but decreased expression of pp-PI3K/t-PI3K, p-Akt/t-Akt, p-mTOR/t-mTOR, ZO-1 and Claudin-5. Compared with the TBI group, the TBI+Dex group exhibited reduced mNSS, brain water content, expression of LC3, TNF-a, IL-1β, INF-γ and IL-6, positive expression of LC3, as well as expression of LC3 I/II and Beclin-1 but demonstrated an elevated expression of pp-PI3K/t-PI3K, p-Akt/t-Akt, p-mTOR/t-mTOR, ZO-1 and Claudin-5, while opposite trends were observed in the TBI+LY group. The TBI+Dex group exhibited reduced mNSS, brain water content, expression of LC3, TNF-a, IL-1β, INF-γ and IL-6, positive expression of LC3, as well as expression of LC3 I/II and Beclin-1 but demonstrated an elevated expression of pp-PI3K/t-PI3K, p-Akt/t-Akt, p-mTOR/t-mTOR, ZO-1 and Claudin-5, while opposite trends were observed in the TBI+LY group, as compared with the TBI+Dex+LY group. CONCLUSION: The data shows that Dex exerts a neuroprotective effect via the activation of the PI3K/Akt/mTOR signaling pathway in rats with TBI.