GnRH signaling is necessary for the establishment of vasopressin and RP3V TH sexual dimorphism. Vasopressin immunoreactivity in the LS of adult intact male (A), intact female (B), and wild-type (C) and GnRHR-KO (D) male mice GDX on P41–P45 and treated with a testosterone capsule for 14 d. E, Quantitative analyses (mean ± SEM) of the density of vasopressin fibers in the LS in intact wild-type male and female mice, and GDX+T wild-type and GnRHR-KO male mice. TH immunoreactivity in the RP3V of adult intact male (F), intact female (G), and wild-type (H) and GnRHR-KO (I) male mice GDX on P41–P45 and treated with a testosterone capsule for 14 d. J, Quantitative analyses (mean ± SEM) of the number of TH-immunoreactive neurons in the RP3V in wild-type intact male and female mice and GDX + T wild-type and GnRHR-KO male mice (n = 4–5/group). Scale bar, 100 μm. Groups were compared using one-way ANOVA with post hoc Student–Newman–Keuls comparisons. Bars labeled with different letters are significantly different from each other at either p < 0.05 or p < 0.01 (see text). LV, lateral ventricle; 3V, third ventricle.