Testosterone and estrogen affect neuronal differentiation but not proliferation in early embryonic cortex of the rat: the possible roles of androgen and estrogen receptors

We examined the effect of testosterone (T) and 17 beta-estradiol (E) on dif ferentiation and proliferation of cultured neurons from the cortex of 14-da y-rat embryos (E14) using immunocytochemistry. We found that the cultures r eceiving E had significantly more neurons with longer neurites than the con trol cultures, while both fewer and less differentiated neurons were seen a fter 24 h of incubation with T. However, neither T nor E changed the number of cells positive for BrdU, a proliferation marker. We also found that the androgen receptor (AR) was markedly expressed in the neurons, whereas the expression of estrogen receptor (ERalpha) was barely detectable. These resu lts suggest that E and T differ in effect on differentiation, while neither affect proliferation in early developmental cortex. Furthermore, since the AR is expressed in the cortical neurons by E14, the inhibitory effect of T on differentiation may be receptor-mediated, while the stimulatory effects of estrogen in the cortex do not appear to involve nuclear ERalpha at this developmental stage. Published by Elsevier Science Ireland Ltd.