| Objective: To observe the change of the brain lipid binding protein (BLBP) expression in dentate gyrus(DG)region of transected and normal hippocampi after the right side of rats′fimbria-fornix transection. Methods: (1)RT-PCR: Thirty-six SD rats were randomly divided into 6 groups, 6 rats in each group. One group served as normal control and the others served as fimbria-fornix transected 1st, 3rd, 5th, 7th and 14th day group, respectively. Then hippocampi were isolated and total RNA was extracted. Semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) method was used in detection of the expression of BLBP mRNA in hippocampus after the right side of rats′fimbria-fornix transection. The relative expression level of BLBP mRNA was indicated by the ratio of the optical density value of BLBP to that of GAPDH. The Stata8.0 software was used in one-factor analysis of variance and comparison between every two groups. (2)Western Blot: Thirty-six SD rats were randomly divided into 6 groups, 6 rats in each group. One group served as normal control and the others served as fimbria-fornix transected 1st, 3rd, 5th, 7th and 14th day group, respectively. Then hippocampi were isolated and the extracts were gained from the fimbria-fornix transected and the normal hippocampi. The expression product of BLBP was detected by Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblot. The relative expression level of BLBP protein was indicated by the ratio of the integral optical density value of BLBP to that ofβ-actin. The Stata8.0 software was used for one-factor analysis of variance and comparison between every two groups. (3)Immunohistochemistry: Thirty-six SD rats were randomly divided into 6 groups, 6 rats in each group. One group served as normal control and the others served as fimbria-fornix transected 1st, 3rd, 5th, 7th and 14th day group, respectively. The rats were perfused and fixed, then cryostat sections of hippocampus were prepared for BLBP immunohistochemistry. Three sections were taken from each rat in first, middle and back hippocampus.The number and gray scale volume of BLBP positive cells in 0.075㎜ 2 aera of hilus and subgranular layer of dentate gyrus were measured, respectively. Paired t-test was used for the number and the gray scale volume of BLBP positive cells with Stata8.0 software. Results: (1)RT-PCR: In normal group, The relative expression level of BLBP mRNA was 0.057±0.019. On the 1st day, the expression level of BLBP mRNA was 0.065±0.013. It started to increase on the3rd day (0.256±0.54) after transection, and the peak appeared on the 5th day (0.719±0.124). Then it started to decrease on the 7th day(0.459±0.099)and closed to the normal level on the 14th day(0.082±0.016). Statistical analysis showed that there were not only statistically significant differences between the normal control group and the 3rd, 5th and 7th day group after transection (P<0.01), but also between the 5th day group and the 3rd, 7th and 14th day group after transection (P<0.01). (2)Western Blot: On the 1st day, the expression level of BLBP protein was 0.602±0.051, which appeared no statistically significant differences by comparing with the normal control group (P>0.05). It started to increase on the 3rd day (1.151±0.078) after transection, and the peak appeared on the 5th day (1.458±0.132). Then it started to decrease on the 7th day(1.043±0.058)and closed to the normal level on the 14th day(0.869±0.088). Statistical analysis showed that except the 1st day, there were statistically significant differences between all the other groups and the control group group (P<0.01); there were also statistically significant differences between each two groups (P<0.01 or =0.01), except between the 3rd day group and the 7th day group , between the 7th day and the 14th day (P>0.05). (3) Immunohistochemistry: The present results showed that few BLBP positive cells were expressed in both sides of each region and subgranular layer of hippocampus in control group. After the fimbria-fornix transection, no significant difference was observed in both sides on the 1st day. Compared with the normal side, more BLBP positive cells with deeper staining were found in the subgranular layer of the transected side on the 3rd day. The number and the color of the larger-body positive cells with growing neurite in subgranular layer of transected side were detected much more than those in normal side and appeared to the peak on the 5th day. Then it started to decrease 7 days later and closed to the normal level on the 14th day. But, the number of the BLBP positive cells showed little difference in both sides of hilus on the 3rd and 5th day after transection, while the color was more deeper in the fimbria-fornix transected side. Seven days later, it also decreased slowly and closed to pre-transection leve1 on the 14th day. Conclusion: The expression level of BLBP mRNA and protein increase after fimbria-fornix transection. The expression of BLBP mRNA and protein are changed with time, that is, those increase at first and then decrease to normal level, and reach peak on the 5th day. BLBP positive cells are expressed in pyramidal layer of hippocampus , subgranular layer and hilus of dentate gyrus in both sides, which are significantly higher in transected side than those in normal side; there are few increased BLBP-positive radial glial cells in hilus of fimbria-fornix transected side by compareing with the normal side, while BLBP-positive radial glial cells markedly increase in subgranular layer, the cell bodys become larger, and the processes grow longer, which show an "activation" phenomenon. The results suggest that the scaffolds of BLBP-positive radial glial cells might conduce to the neural stem cells migration and the differentiation to the neurons.
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