Objective To investigate the neuroprotective effect of vagus nerve stimulation ( VNS) on a model rat of focal cerebral ischemia. Methods A total of 42 adult male Sprague-Dawle ( SD) rats were randomly divided into a sham operation group (n=10),a model group (n=16),and a VNS-treated group ( n = 16 ) . Each group was randomly redivided into 2 subgroups:left VNS subgroup and right VNS subgroup. A model of focal cerebral ischemia (2 h) in rats was induced by the intraluminal suture method. At 30 minutes after modeling, the VNS-treated group received cervical VNS, the stimulation intensity was 0. 5 mA,the interval was 0. 5 ms,and the frequency was 20 Hz. Stimulation was once every 5 min within 1 h and each lasted for 30 s. The model group did not give any stimulation. Neither blood vessels were embolized nor were the nerves stimulated in the sham operation group. The changes of somatosensory evoked potentials ( SEP) on the lesion sides during operation were monitored. At 24 h after modeling,the neurobehavioral scores were performed. The rats were sacrificed,and their brain infarct volume was measured. Results (1) During the stimulation of left VNS in rats,the neurobehavioral scores of the sham operation group,model group and VNS-treated group were 0. 4 ± 0. 2,9. 5 ± 0. 4,6. 4 ± 0. 3,respectively;during the stimulation of right VNS in rats,the neurobehavioral scores of the 3 groups were 0. 6 ± 0. 2,9. 3 ± 0. 4,and 6. 9 ± 0. 4,respectively. There were significant differences between the scores of the model group and those of the other 2 groups (P<0. 05). (2) Compared with the model group,the brain infarct volume of the VNS-treated group was reduced ( stimulating the left VNS of the 2 groups was 120 ± 7 and 56 ± 7 mm3 respectively;stimulating the right VNS was 115 ± 10 and 54 ± 8 mm3 respectively ) . There were significant differences ( P <0. 05). (3) Compared with the sham operation group and the VNS-treated group,the SEP N1 amplitude of the model group was decreased significantly and the P1 latency was prolonged significantly. There was significant difference (P<0. 05). (4) There were no significant differences in the stimulation of the left or right VNS in the VNS-treated group among the infarct volume, neurobehavioral scores, SEP amplitude,and latency (P>0. 05). Conclusion No matter whether to stimulate the left or right vagus nerves, they both have neuroprotective effects on ischemic brain injury, and there was no significant difference on the action effects.