Sex steroids and the development of the newborn mouse hypothalamus and preoptic area in vitro: III. Effects of estrogen on dendritic differentiation.

Gonadal steroids have previously been shown to enhance neuritic outgrowth from mouse preoptic area explants in vitro. To examine effects within the explant proper, dendritic fields of Golgi-stained neurons of estradiol-treated and untreated cultures were compared quantitatively. Neurons of gonadal steroid-treated cultures had significantly more dendrites arising from the cell body. Since bifurcation probability did not differ between the treatments, the primary effect of estradiol treatment appears to be induction of dendritic branches from the soma. This indicates that intra-explant dendrites, like extra-explant neurites, proliferate in response to estradiol treatment and suggests the involvement of hormone-stimulated dendrogenesis in sexual differentiation of the brain.