Expression of neurotrophic factor in hippocampus and its correlative factors after status convulsion

Objective To investigate the expression of brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF) in hippocampus after status convulsion (SC) and explore the influence of age and duration of SC on the expression of BDNF and NGF. Methods Animal model with the different durations of SC (30 min,3h) were established by intraperitoneal injection of 3 mEq/kg lithium chloride,18-20 h later,followed by 5 mg/kg pilocarpine in 40 adult Wistar rats aged 2-3 months and 40 20-day-old Wistar rats. The normal control and experimental control were made in ten adult rats and ten 20-day-old rats (n=5 for each control). The rats were sacrificed at 3 h,6 h,12 h,1 d,3 d,7 d after 30-minute SC,or 3 h,1 d after 3-hour SC respectively. The location and cell type expression of BDNF and NGF in the hippocampus were observed by immunohistochemistry. The levels of BDNF and NGF at different time points were quantitatively analyzed by enzyme-linked immunosorbent assay (ELISA). Results The cells expressing BDNF and NGF located mainly in the dentate granule cells and CA1-CA4 pyramidal cells of hippocampus. The most positive immunoreactivity was in cytoplasm,partly in axons. The expression of BDNF had the tendency of increase in all rats after 3-hour SC,peaked at 1 d and 3 d respectively. These increases lasted for at least 7 d. Moreover,a several-fold increase was observed at the peak levels. The patterns of NGF expression were similar to that of BDNF after SC. The elevated degree and duration of NGF expression were remarkably lower than that of BDNF,declining abruptly to below control levels by 12 h with the characteristic of biphasic increase. The expression of hippocampal BDNF had the positive correlation with the duration of SC,but that of NGF was not. No matter the duration of SC,there was more rapid and evident induction of BDNF in 20-day-old rats and adult rats. Moreover,the age-related difference was more obvious for the longer duration of SC. Conclusion SC induced the expression of BDNF chiefly in hippocampus,and had minor influence on that of NGF. The expression of BDNF was related to age and duration of SC. There was a more rapid and marked induction of BDNF in 20-day-old rats and adult rats. The age-related difference had the positive correlation with the duration of SC.