The relative amount (mean ± sem) of PR-ir in the MPOA on P0, P5, P10, P15, P20, and P25 in male (M) and female (F) mice that were either WT or ArKO. *, Post hoc comparisons indicated a significant (P < 0.05) sex difference in WT mice at the ages indicated. Post hoc comparisons also indicated significant (P < 0.05) differences between WT vs. ArKO females (F over brackets) and between WT and ArKO males (M over brackets) at the ages shown.