As shown in Figure 5, C57BL/6J mice, which have a higher degree of depression than BALB/c mice, had fewer c-Fos-positive cells in the NAc Core regions (Core; p = 0.0007, Mann–Whitney test, Shell; t(7) = 1.670, p = 0.1388, unpaired t-test). This evidence concerns the gene FOS and depressive disorder.