Abstract
Sex steroids play an important role in regulating neuroendocrine and sexual behavior. These responses to sex steroids are primarily specific to the steroid receptor-containing neuronal system. The circuitries involved in neuroendocrine and behavioral functions are under the direct control of gonadal steroids throughout life.
In perinatal animals, gonadal steroids affect brain sexual differentiation by regulating the number of target neurons, stimulating axonal and dendritic growth, modifying synaptic connectivity and maintaining neuronal survival. These steroidal actions in perinatal animals are organizational and irreversible, whereas they are activational in adult animals.
Neuronal plasticity to gonadal steroids in the neuroendocrine brain is detectable at different sequences of the developmental process and after aging. At the synaptic level, some evidence suggests that estrogen prevents age-dependent decreases of synaptic density in certain neuronal groups, presumably by facilitating neuronal plasticity.
