9729643 McCarthy Throughout the mammalian lifespan, the central nervous system is a target organ for the actions of steroid hormones. This is most clearly illustrated in the developing brain where exposure to gonadal steroid hormones permanently change its structure and function. Indeed, differences in behavior between males and females result from differential exposure to androgens and estrogens during a sensitive period of development. The hypothalamus is one of the critical brain regions where steroids modulate neuronal activity. While most of the research is directed towards understanding the mechanisms by which steroids hormones interact with neurons, the brain is also packed with non-neuronal glial cells. Recently, it has become clear that glial cells modulate neural development and activity, and can undergo remodeling in response to fluctuation in gonadal steroid levels. Dr. McCarthy has reported that there are enormous changes in the morphology of glia in the hypothalamus after exposure to testosterone during the first few days after birth. She will now determine the significance of these morphological changes by further characterizing the steroid modulation of neonatal glia in regards to steroid sensitivity, specificity, and site of action. Moreover, Dr. McCarthy will use state of the art microscopy to analyze the mechanism of neuronal-glial communication with sexual dimorphic regions within the hypothalamus. These studies will determine how changes in the shape of glial cells impact on that of the nearby neurons and alters brain development. Understanding how gonadal steroids influence the developing brain helps us to understand the etiology of neurological disorders that effect males and females differently as well as serving as an excellent model for examining the complex process of normal brain development and neural plasticity. The results will also help us elucidate how the basic structure of the brain is related to behavior.
