Fig. 1: Acute novelty stress decreases food intake, induces anxiety and activates NPY^DRN/vlPAG neurons.

a Acute novelty stress paradigm. Group-housed mice were individually transferred into new cages without padding to induce acute novelty stress. 4-h (b), 4–24-h (c) and 24-h (c) food intake under acute novelty stress and non-stress conditions. n = 10 cages (50 mice) for non-stress group and n = 50 mice for novelty stress group. In this study, the food intake of group-housed mice was calculated by dividing the total food per cage by mice number in the cage. In (b) Two-way ANOVA with post-hoc Šídák’s multiple comparisons test. In (c) Two-sided unpaired Student’s t test. d The levels of serum corticosterone before and 1 h after novelty stress. Two-sided paired Student’s t test. e Representative elevated plus maze (EPM) traces of non-stress and novelty stress groups. The gray shades indicate the closed arms. f Percentages of open-arm time in the EPM. Two-sided unpaired Student’s t test with Welch’s correction. g Representative open field test (OFT) traces of non-stress and novelty stress groups. The gray shades indicate the center arena. h Percentages of time, travel distance in the center area and total travel distance of OFT. Two-sided unpaired Student’s t test. i 2-h novelty stress induced Fos (purple) signals in NPY^DRN/vlPAG neurons (green) from Npy^GFP mice. Representative images (i) and quantitative data (j). In (i), blue represents DAPI staining and arrows indicate Fos⁺NPY⁺ neurons. The rightmost panels are magnified images. In (j), for percentage among Fos⁺ neurons, two-sided unpaired Student’s t test; For percentage among NPY⁺ neurons, two-sided unpaired Student’s t test with Welch’s correction. k Fiber photometry recording setup. l NPY^DRN/vlPAG calcium signals in mice individually transferred to a novel cage without padding for 1 min and back to home cages. Two-way ANOVA with post-hoc Šídák’s multiple comparisons test. Right: Average calcium changes when mice were in new cages (20–40 s) and home cages (80–100 s). Two-sided paired Student’s t test. Data are shown as mean ± SEM. Unless specified, ‘n’ refers to mice number. Source data are provided as a Source Data file.