Fig. 1

Cell proliferation in the early developing hippocampus is modulated by estradiol signaling in a sex-specific manner. Neonatal male rats have twice as many proliferating cells as females in the dentate gyrus and CA1 regions. Inhibition of estradiol synthesis or estrogen receptor (ER) antagonism decreases proliferation in males to the same levels as females, but neither testosterone nor estradiol will further increase proliferation in males above baseline. Both testosterone and estradiol increase the number of proliferating cells in females to the same level as males, while inhibition of estradiol synthesis and ER antagonism has no effect