CX3CR1−/− mice show decreased hippocampal neurogenesis in a gene-dose dependent manner (a, b). Unbiased stereology revealed a significant decrease in the number of DCX+ cells in the SGZ of adult male CX3CR1−/− and CX3CR1+/− mice compared to wild-type mice (p< 0.001). CX3CR1−/− were also significantly different from CX3CR1+/− (p<0.05) (a). Quantification of the number of cells that were proliferating during the preceeding 24 hours as determined by the incorporation of BrdU, was significantly fewer in the CX3CR1−/− and CX3CR1+/− mice compared to wild-type (p<0.001). CX3CR1−/− were also significantly different from CX3CR1+/− (p<0.05) (b). Wild-type (WT, white bar), CX3CR1+/− (gray bar), CX3CR1−/− (black bar). All data are presented as mean ± SEM p < 0.01