Schlinger 9602139 It is widely recognized that the gonadal steroid hormones have profound effects on the developing brain and on the function of the adult central nervous system. Interestingly, in both males and females of many species, estrogens exert some of the most dramatic effects. However, it is not always clear how estrogens reach estrogen-sensitive brain regions nor is it clear how estrogens act to influence neuronal growth or function. In the brain of some species, there is a remarkable neural circuit that controls the organism's ability to learn during development and to translate the learned information into behavior as an adult. Estrogens are implicated in the initial growth of this circuitry during early development, in the neural mechanisms underlying learning, and in the activation of adult behavior. All estrogens are derived from androgens, a reaction catalyzed by the enzyme aromatase. In males, circulating androgens are converted to estrogens locally in the brain. It is these estrogens that act to masculinize the developing brain and then activate masculine adult brain function. In some species, aromatase is present in the neural circuitry underlying learning, which may be associated with the effects of estrogen on learning. Dr. Schlinger is continuing his investigations into the role of aromatase and estrogen on estrogen-dependent learning and behavior, and will conduct cross-species experiments to characterize the effects of estrogen more clearly. By clarifying properties of steroid synthesis and function in brain, we will gain a better understanding of how activities of the neural and endocrine systems are coordinated in regulating neural function. In addition, these investigations provide a mechanism to further foster species survival in natural environments and gain a better understanding of events crucial to reproduction in the wild.
