(a) The region of the preoptic area (labeled here as MPO) used for the analysis is shown, with the region of interest indicated with a green outline. (b) A representative image of BrdU nuclear labeling in the POA of a DMSO female pup whose dam was injected with BrdU on E14. The region of interest outlined in green (a) is shown at ×20 magnification in (b). White scale bar = 25 μm. The brain map shown in (a) was modified from Paxinos (1991). BrdU, bromo-2-deoxy-5-uridine; DMSO, dimethyl sulfoxide; E14, Embryonic Day 14; MPO, medial preoptic area; POA, preoptic area