The Dynamic Changes Of Neurotrophin-3 Expression In Brain In Experimental Streptococcus Pneumoniae Meningitis

AIM:To investigate the expression of neurotrophin-3(NT -3)protein in infancy rats and to investigate the relationship between the expression of NT-3 and antibiotic was administed after exposure to experimental Streptococcus pneumoniae meningitis;To investigate the relationship between dexamethasone was administed and expression of neurotrophin-3 in experimental Streptococcus pneumoniae meningitis.Methods:1.Three weeks old rats were used to construct the models of Streptococcus pneumoniae meningitis(n=20)and mormal(n=12).At 24 h,5d after inoculating,the expression of NT-3 protein were detected by immunohistochemical staining methods in cerebral cortex and hippocampus.2.To construct the models of Streptococcus pneumoniae meningitis(n=8)and mormal (n=6)in 3 weeks old rats,then they were administed by antibiotic respectively. Neurotrophin -3 protein in cerebral cortex and hippocampus were detected by immunohistochemical staining methods,respectively.3.To construct the models of Streptococcus pneumoniae meningitis in 3 weeks old rats(n=8)and mormal(n= 6),then they were administed by antibiotic plus dexamethasone respectively. neurotrophin-3 protein in cerebral cortex and hippocampus were detected by immunohistochemical staining methods,respectively.RESULTS:In cerebral cortex and hippocampus,the expression of NT-3 protein was declined obviously at 24 h(P＜0.05)compared to controls and then restored at 5 days(P＜0.05)in this experiment,but the expression of NT -3 protein at 5 days still was lower than the 5 days control levels(P＜0.05).The expression of neurotrophin-3 protein of the group after administration by antibiotics after infection 5 days was lower than the 5 days control levels after administration by antibiotics(P＜0.05),and it was identical compare to the group after infection 5 days(P＞0.05);In control,The expression of neurotrophin -3 protein after administration by antibiotics,there was no change compared to 5 days control levels(P＞0.05).After administration by antibiotics plus DEX,the expression of neurotrophin-3 protein compare to administration by antibiotics was greater after infection 24 h(P＜0.05),but was lower than the control levels(P＜0.05);In control,after administration by antibiotics plus DEX,the expression of neurotrophin -3 protein was greater than that in cerebral cortex and hippocampus after administration by antibiotics after infection 24 h(P＜0.05).There are no positive staining consequence in negative control.CONCLUSIONS:These results support the hypothesis:1.NT -3 might not play its neuroprotective role in brain damage process because of NT -3 protein being declined in streptococcus pneumoniae meningitis attacked rats.2.The expression of neurotrophin-3 was lower after administration by antibiotics in streptococcus pneumoniae meningitis and low level of neurotrophin-3 still can not restore its neuroprotective role.3.DEX might be propitious to resist brain injury in streptococcus pneumoniae meningitis by up-regulation the expression of neurotrophin-3 protein.