Objective To investigate the effects of magnesium sulfate and magnesium L-sulfonate on the neurobehavioral response and the expression of induced nitric oxide synthase (iNOS) in neurons after acute cerebral ischemia in rats. Methods One hundred and twelve male Sprague-Dawley ( SD) rats were double-blinded randomly divided into sham-operated group, middle cerebral artery occlusion ( MCAO ) group,MgSO4 treatment group,L-MgT treatment group. Each group was further divided into 6 h,12 h and 24 h subgroups according to the different detection time points. Rat MCAO models were produced following the Longa's method. And the Longa score,limb-placing test,rotarod test,and sticky tape test were performed to evaluate the neurological damage,autonomous movement and coordinate perception in the 24 h subgroup. At the end of the experiment,2,3,5-triphenyltetrazolium chloride ( TTC) was used to evaluate the area of cerebral infarction at 24 h reperfusion. Immunohistochemical staining was employed to determine the altera-tions in iNOS expression in neurons 6 h,12 h and 24 h after reperfusion. Results In behavioral evaluation:Longa score:Normal performance was observed in sham-operated group. Compared with the MCAO group,the scores of MgSO4 treatment group(1. 71±0. 18) and L-MgT treatment group(1. 14±0. 14) were decreased (t=0. 548,3. 873,all P<0. 05),and the score of L-MgT treatment group was lower than that of the MgSO4 group(t=2. 828,P<0. 05). Limb symmetry score:There was no statistically significant difference between MgSO4 group and MCAO group,but there was a statistically significant difference between L-MgT group and MCAO group (t=7. 071,P<0. 05). The roding experiment:The time of MgSO4 group and the L-MgT group were significantly different from that of the MCAO group (t=9. 588,20. 776,P<0. 05),and the time of the L-MgT group was significantly higher than that of the MgSO4 group (t=4. 983,P<0. 05). The right limb strip removal experiment: The time of MgSO4 group and L-MgT group were statistically different from that of MCAO group (t=6. 135,5. 825,P<0. 05),and the time of L-MgT group was increased compared with that of MgSO4 group(t=4. 507,P<0. 05). TTC test:No infarction was formed in the sham group. Compared with MCAO group ((36. 82±1. 35)%),the cerebral infarction volume of MgSO4 group ((17. 39±1. 72)%) and L-MgT group ((10. 81 ± 1. 35)%) significantly decreased, with statistically significant differences ( t=8. 874,11. 105,P<0. 05). Compared with MgSO4 group,cerebral infarction volume in L-MgT group was sig-nificantly reduced,with statistical significance (t=2. 593,P<0. 05). HE staining:There was no statistically significant difference in cell morphology between MgSO4 group and MCAO group at each time point,but the cell morphology of L-MgT group was intact compared with that of MCAO group. INOS staining at 24 h:There was no statistically significant difference in the positive cell density between the MgSO4 group and the MCAO group,but the L-MgT group (cortex:(196. 7±8. 1);striatum:(153. 3±3. 8)) positive cell density was lower than that of the MCAO group (cortex:(375. 0±6. 7),striatum:(358. 3±4. 5)),and the difference was sta-tistically significant (t=11. 113,36. 231,P<0. 05). Conclusion L-MgT may have a significantly protective effect on MCAO rats,and its mechanism may be related to the level of iNOS in neurons.