(A–J) Coronal sections through the adult brain of male and female mice harboring the aromatase-IPIN allele stained for βgal (A–F) or PLAP activity (G–J). There are more aromatase+ cells in the male BNST and MeA, and in the female caudal hypothalamus (CH). PLAP+ fibers occupy a larger volume in the male AH (white arrow) and in the region (arrows) surrounding the VMH (dashed outline). (K–O) Nissl stained sections depicting locations of the BNST, MeA, CH, AH, and VMH. (P) Quantitation of sexual dimorphism in cell number (βgal+) and fiber tracts (PLAP+) of neurons expressing aromatase. Mean ± SEM; n ≥ 3; * p ≤ 0.015, ** p ≤ 0.005. Scale bars equal 500 μm (A, B) and 250 μm (C–J).