Objective To explore the neuroprotective effect of dexmedetomidine (Dex) in rats exposed to focal cerebral ischemia/reperfusion (I/R) induced by middle cerebral artery occlusion (MCAO) and the possible mechansims. Methods Adult male Sprague-Dawley rats were subjected to MCAO for 90 min followed by reperfusion for 24 h and Dex (15 μg·kg-1) was infused through the left femoral vein immediately after the onset of MCAO. The PI3K inhibitor LY294002 (LY, 10 mM, 10 μl) or eNOS inhibitor L-NIO (1 mg·kg-1, 10 μl) was intracerebroventricular administered before ischemia using a microinjecton. The neurological deficit score, brain edema, cerebral infarct volume, and neuron survivals were evaluated after 24 h of reperfusion. The expression of p-Akt (Ser473) and p-eNOS (Ser1177) in the ischemic hemicerebrum was detected by Western Blot. Results Compared with I/R group, the neurological deficit score, cerebral infarct volume, and the degree of brain edema were significantly reduced in the rats treated with Dex((2.3±0.4) vs (3.9±0.6), (19.3±3.5)% vs (40.5±5.4)%, (61.8±8.1)% vs (76.3±8.5)%, all P 0.05). Conclusion Dex can reduce cerebral injury in rats exposed to focal I/R, which is mediated by the activation of PI3K/Akt-eNOS pathway. Key words: Dexmedetomidine; Middle cerebral artery occlusion; PI3K; Akt; Endothelial nitric oxide sythanse