FIG. 5.
Progressive neuronal cell loss is attenuated in the dentate gyrus (DG) of CD1−/− mice after traumatic brain injury (TBI). (A–C) Unbiased stereological quantification of neuronal cell loss in the CA1 (A), CA2/3 (B), and DG (C) sub-regions of the hippocampus at 24 h, 7 days, and 21 days. Neuronal loss was observed in the CA1 and CA2/3 regions within 7 days of the injury, with no significant further loss at 21 days. Progressive neuronal loss was observed in the DG, and CD1−/− mice had attenuated neuronal loss in this region at 21 days (*p=0.004 versus CD1+/+ mice). Analysis by one-way analysis of variance (ANOVA) was done with Tukey's post-hoc corrections in A–C for comparisons across different time points. One-tailed paired Student's t-test was done for comparison to the CD1+/+ group at each time point (ap<0.01 versus sham animals; bp<0.001 versus the 24-h groups; cp<0.01 versus the 7-day groups; mean±standard error of the mean; n=3–4/group). (D) Linear regression analysis comparing TBI-induced neuronal loss in the DG with latency to reach the submerged platform on day 17 post-injury of the Morris Water Maze (MWM). Pearson's correlation (p<0.0001; r2=0.90). (E) Linear regression analysis comparing TBI-induced neuronal loss in the DG with time spent in the target quadrant in the probe trial of the MWM (p<0.0001 by Pearson's correlation; r2=0.96). (F) Linear regression analysis was done comparing TBI-induced neuronal loss in the DG with the discrimination index (D.I. %) in the novel object recognition test (p<0.0001 by Pearson's correlation; r2=0.96).