Neuroprotective effect of magnesium-L-sulfonate on focal cerebral ischemia in rats and its mechamism

Abstract

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 alterations 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 significantly 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 statistically 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. Key words: Cerebral ischemia; Magnesium sulfate; Magnesium L-threonate; Neurological function; Inducible nitric oxide synthase; SD rats