Fig. 1: Calb1 expression in the vHC regulates stress susceptibility.

a Experimental timeline of sample collection, chronic SD exposure, and the SI test. b Schematic illustration of sample collection from the vHC. A guide cannula was implanted into the vHC (left), and a metal wire (cyan) was then inserted through the cannula to collect a tissue sample (right). c Trajectories of representative susceptible (left) and resilient (right) mice in the SI test. The orange regions represent the interaction zone. d Heatmap showing hierarchical clustering of gene expression patterns collected from the vHC before SD stress. After SD stress exposure, three stress susceptible and four stress resilient mice were identified in subsequent SI tests and their gene expression patterns were compared. The 80 genes that showed a more than 2-fold difference in expression with a P value < 0.05 (corresponding to e) between the two groups are shown. e Volcano plot showing the fold change in the expression of and P value of individual genes in stress susceptible mice compared with stress resilient mice. The vertical dotted lines represent a 2-fold difference, and the horizontal dotted line represents the significance cutoff (one-sided Student’s t-test, P  =  0.05). The red and blue dots indicate significantly upregulated and downregulated genes, respectively, in stress-susceptible mice. f qPCR analysis of the expression levels of Calb1 (n = 13 and 9 mice). Box plots show center line as median, box limits as upper and lower quartiles, whiskers as minimum to maximum values. Z = 2.00, *P = 0.045, two-sided Mann–Whitney U test. g Structures of the AAV constructs. h Experimental timeline of virus injection. i Representative images showing the expression of Calb1 (green) and mCherry (shRNA, red) in the vHC in AAV-shCalb1-injected mice. The white boxes in the top panels are magnified in the bottom panels and show knockdown of Calb1 in shRNA-expressing ventral hippocampal neurons. j Same as i but for AAV-shScr-injected mice, showing highly overlapping expression of Calb1 and shRNA. k SI ratios of non-SD, SD mice, and SD mice injected with AAV-shCalb1 and AAV-shScr into the vHC (n = 12, 73, 12, and 8 mice). Each dot represents one mouse. Non-SD versus SD, Z = 3.73, **P = 5.7 × 10⁻⁴; SD versus AAV-shCalb1, Z = 4.23, **P = 2.3 × 10⁻⁵; SD versus AAV-shScr, Z = 0.82, P > 0.99, two-sided Mann–Whitney U test followed by Bonferroni correction.