| Objective: The purpose of this study was to evaluate 1) thechanges of neurologic impairment and infarct cerebral volume; 2) the progressive characters of astrocytes on morphological alterations, quantity, distribution and so on; 3) the influence of PTS upon those items as mentioned above at different durations of reperfusion following focal cerebral ischemia in rats.Metheods: 1) 120 male Sprague-Dawley rats (w=280-300g) wereused in this study, and all animals were randomly devided into N. S treated (n=48), PTS treated (n=48) and sham (n=24) operated group. Reversible middle cerebral artery occlusion was performed by improved thread embolism method. After 2 h of ischemia, the nylon monofilament was withdrawn to allow reperfusion for 3 h, 6 h, 12 h, 24 h, 48 h, 72 h, 7 d, 14 d. 2) PTS was administered by intraperitoneal injection (50mg/kg) once a day and lasted 6 days till operation, and the administration repeated once at 2 h before ischemia. The medicine was substituted by saline in N. S treated group; Sham operated rats were subjected to same operation except for the insufficiency of the length (<10 mm) of filament inserted into the internal carotid artery (ICA). 3) In this report, the neurological deficit grades and the volume of the cerebralinfarction were estimated by 2 % TTC staining and Zea Longa' s method, and H&E staining, immunohistochemical methods were adopted to investigate the morphological characters of neurons and astrocytes in the ischemic area of rat bain.Results: 1) The neurological deficit scores ranged from 1 to 3, and no significant difference existed on the scores between the N.S and PTS-treated groups except for at 72 h after reperfusion. The rats had their largest cerebral infarct sizes at 24 h after reperfusion, the mean ratio of the infarct volume to the total volume of forebrain was 18. 5% and 12. 4 % in N.S and PTS-treated groups respectively, and up to 14 d, the number became 8. 2 % and 4. 4 %; 2) Compared with the Sham control group, the expression of Nestin started to increase at 6 h, and peaked at 7 d, then dropped at 14 d, but it was still significantly higer than that of normal level. The expression of GFAP enhanced at 3 h, and continued to boost up till the end of observation; 3) At 3 h after reperfusion, the proportion of intact neurons in the ischmic penumbra was 73.3 % in the N. S control group, declined to 46.3 % at 14 d, and the number of that in the PTS treated group was 71.1%, 57.5 % respectively; 4) During 24 h to 7 d after reperfusion, the number of Nestin positive cells in the PTS treated group was more than that of the N. S control group, and the similar phenomenon of GFAP occured during 12 h to 14 d; 5) Except for the Sham contral group, the mean proportion of NestinVGFAP+cells to the total number of Nestin contained cellswas about 80%; In the N. S treated group, the number of NestinVGFAP +cells began to rise at 48 h after reperfusion, and peaked at 7 d; 6) In the PTS treated group, the proportion of NestinVGFAP" and Brdu'/Nestin*cells up-regulated at 7 d after reperfusion , and it showed a significant difference compared with the N.S group(p <0. 05).Conclusion: 1) PTS could reduce effectively the infarctbrain volume following focal cerebral ischemia; Though the neurologic deficiency had no significant improvement except for at 72 h, the infart size detected reduced in fact, and it revealed that the neurological scores could not reflect correctly the actual infarct cerebral volume in rat. 2) The number of reactive astrocytes increased since early period of reperfusion, and reactive astrocytes started to proliferate at 48 h. 3) The number of intact neurons in the ischemic penumbra was declining gradually, and it seemed to be relatively stable after 7 d of reperfusion. 4) The majority of Nestin contained cells belonged to astrocytes, and neural stem cells seemed to involve in the neural restoration after ischemic injury. 5) PTS could increase the expression of GFAP & Nestin and promote the proliferation in rat brain after middle cerebral artery occlusion and reperfusion, which might be the one of protective mechanisms of PTS against ischemic injury.
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