Electroacupuncture preconditioning at acupoint Baihui (GV20) can reduce focal cerebral ischemia/reperfusion injury.However,the precise protective mechanism remains unknown.Mitochondrial fission mediated by dynamin-related protein 1 (Drpl) can trigger neuronal apoptosis following cerebral ischemia/reperfusion injury.Herein,we examined the hypothesis that electroacupuncture pretreatment can regulate Drp1,and thus inhibit mitochondrial fission to provide cerebral protection.Rat models of focal cerebral ischemia/reperfusion injury were established by middle cerebral artery occlusion at 24 hours after 5 consecutive days of preconditioning with electroacupuncture at GV20 (depth 2 mm,intensity 1 mA,frequency 2/15 Hz,for 30 minutes,once a day).Neurological function was assessed using the Longa neurological deficit score.Pathological changes in the ischemic penumbra on the injury side were assessed by hematoxylin-eosin staining.Cellular apoptosis in the ischemic penumbra on the injury side was assessed by terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick end labeling staining.Mitochondrial ultrastructure in the ischemic penumbra on the injury side was assessed by transmission electron microscopy.Drpl and cytochrome c expression in the ischemic penumbra on the injury side were assessed by west blot assay.Results showed that electroacupuncture preconditioning decreased expression of total and mitochondrial Drpl,decreased expression of total and cytosolic cytochrome c,maintained mitochondrial morphology and reduced the proportion of apoptotic cells in the ischemic penumbra on the injury side,with associated improvements in neurological function.These data suggest that electroacupuncture preconditioning-induced neuronal protection involves inhibition of the expression and translocation of Drp1.