Quantification of BrdU-positive cells in p75NTR (+/+) and (-/-) mice. Dentate gyrus volume and numbers of BrdU-positive cells were measured in coronal sections harvested from p75 NTR (+/+) and (-/-) mice. Tissues were obtained one day following the 6-day BrdU injection protocol. (A) Cell counts (as determined by stereological estimates (as described in Methods) in p75 NTR (-/-) mice (n = 14 mice) were significantly decreased compared to those in p75 NTR (+/+) mice (n = 9). *** p < 0.001 between groups, using Student-Newman-Keuls test after ANOVA. For each mouse the cell counts in right and left dentate gyri were averaged. (B) No difference in volume of the granular cell layer was detected between p75 NTR (+/+) and (-/-) mice (mean ± SE; n = 6 mice per group).