Glucocorticoids are hormones secreted from the adrenal glands of animals and human beings. These hormones are known to influence brain function and behavior in both adult and developing organisms. The hippocampus, a brain area involved in memory and learning, is a particularly important target site of glucocorticoid action. Previous research has demonstrated that altered glucocorticoid levels early in life significantly modify the development of the hippocampus, yet few studies have examined the functional consequences of these changes in brain organization. Dr. Meyer will perform experiments in which young laboratory rats will be exposed to either very low glucocorticoid levels (by surgically removing their adrenal glands) or high levels (produced by injection of hormones into non-operated animals). Appropriate control procedures will also be performed. All subjects will subsequently be tested in a spatial-learning task, the Morris water maze, that critically depends on the hippocampus for normal performance. Separate animals from each group will be studied at different ages, thereby enabling Dr. Meyer to detect disturbances in the normal developmental appearance of spatial-learning ability. These experiments will provide important new information about the role of glucocorticoids in normal behavioral development as well as the potential deleterious effects of early exposure to high levels of hormones, as sometimes occurs in human clinical situations.
