The activation profiles of MS neurons respond to body fluid changes. a, Fos-labeling strategy using a TRAP2 system. b, Experimental timelines for identifying brain activation induced by thirst or water satiety using a FosTrap assay in TRAP2 × Ai47 mice. c,d, Representative confocal images (c) and quantification (d) of Fos expression changes in upstream regions of the SFO under different conditions (n = 3 in…