| Objective: (1) To compare the neuroprotective effects of different doses of lithium chloride on the neurons in the CA1 region after transient global ischemia in gerbils. (2) To observe the effect of lithium on cerebral neuronal apoptosis and behavioral impairment in gerbils after transient global ischemia and reperfusion. (3) To investigate the mechanisms of neuroprotective action of lithium.Methods: The transient global ischemia model of gerbils was prepared by clamping the bilateral common carotid arteries for 5 min. In experiment one, 114 gerbils were randomly divided into normal control group (group NC), sham-operated group (group SH), ischemia-reperfusion group(group IR), preconditioning with 1, 3 or 5 mEq/kg lithium chloride group (group LI-1-Pre, LI-3-Pre or LI-5-Pre), treating with 3 mEq/kg lithium chloride group(group LI-3-Post). Gerbils in group LI-Pre were injected intraperitoneally with lithium chloride, 1, 3 or 5 mEq/kg, respectively, once a day for 7 consecutive days before operation. Gerbils in group LI-3-Post were injected intraperitoneally with lithium chloride 3 mEq/kg just before reperfusion, and followed by intraperitoneally injection of lithium chloride once a day for 6 consecutive days. Normal saline was used instead of lithium in group SH and group IR as vehicle control. Gerbils in group SH, group IR, group LI-1-pre, group LI-3-pre, groupLI-5-pre, group Li-Post were further divided into 3 subgroups, according to the time of reperfusion, with 6 gerbils in each. At various periods of reperfusion, all gerbils were perfusion-fixed, and the brain was made into paraffin sections for HE stain, the extent of neuronal injury inthe CA1 region of the hippocampus was observed by light microscope. In experiment two, 78 gerbils were randomly divided into group NC, group SH, group IR, group LI-3-Pre and group LI-3-Post. At the end of the behavioral assessment, all gerbils were perfusion-fixed and the brain was made into paraffin sections for TUNEL stain and immunohistochemistry stain against p53, NF- k B, Phospho-Akt protein respectively. All data were expressed as mean + SD, statistical analysis was performed using SPSS 11.0 and P value of<0.05 was considered significant. Result: (1) HE stain The density of the pyramidal cells in the CAl region decreased time-dependently. The living pyramidal cells in the CAl region of group Ll-Pre or LI-3-Post were significantly greater than those of group IR on the 3rd day or 7th day after reperfusion (p<0.01). On the 3rd day after reperfusion, the living pyramidal cells in the CAl region of group LI-3-Pre or LI-5-Pre was obviously greater than those of group LI-1-Pre (P<0.05), but cortex neuronal injury in group LI-5-Prewas more severe than that in group LI-3-Pre or LI-1-Pre. Therefore 3 mEq/kg lithium chloride was selected for the further study. (2) Behavioral testing Open field testing showed that the gerbils in group IR crossed more squares than those of group SH (p<0.01), the numbers of squares crossed in group LI-3-Pre or LI-3-Post were significantly less than those in IR groups (p<0.01). In the T maze testing, compared with group SH, gerbils in group IR showed significantly working memory impairment (p<0.01). Preconditioning or treating with lithium chloride could significantly attenuate the working memory impairment (p<0.01). (3) TUNEL stain Compared with group IR, TUNEL positive cells in group LI-3-Pre or LI-3-Post were significantly reduced on the 3rd day after reperfusion. (4) Immunohistichemistry stain In group IR, the expression of P53 protein was increased on the 1 st day after reperfusion, obviously increased on the 3rd day and significantly decreased on the 7th day after reperfusion, but still maintained at a high level. The expression of P53 protein in groupLI-3-Pre or LI-3-Post was obviously lower than that in group IR (P<0.01). Compared with group IR, the expression of NF- kB protein in group LI-3-Pre or LI-3-Post was obviously decreased on the 3rd day after reperfusion(P<0.01). The expression of Phospho-Akt protein in the cortex of group LI-3-...
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