ONTOGENY OF SEX-DIFFERENCES IN THE MAMMALIAN HYPOTHALAMUS AND PREOPTIC AREA

1. There are numerous sites in the nervous system where steroid hormon es dramatically influence development. Increasing interest in mechanis ms in neural development is providing avenues for understanding how go nadal steroids alter the ontogeny of these regions during sexual diffe rentiation. 2. An increasing number of researchers are examining effec ts of gonadal steroids on neurite outgrowth, cell differentiation, cel l death, cell migration, and synaptogenesis. The interrelated timing o f these events may be a key aspect influenced by gonadal steroids thro ughout development. 3. The preoptic area and hypothalamus are characte ristically heterogeneous in terms of cell type (e.g., different neurop eptides) and cell derivation. Perhaps a major reason for the ontogeny of sexual differences in the preoptic area and hypothalamus lies in th e convergence of many different cell types from diverse sources (i.e., proliferative zones surrounding the lateral and third ventricles, and the olfactory placodes) that can be influenced in an interactive mann er by gonadal steroid mechanisms. 4. The characterization of multiple mechanisms (e.g., trophic, migratory, apoptotic, fate, etc.,) that con tribute to permanent changes in brain structure and ultimately functio n is essential for unraveling the process of sexual differentiation.