Age related changes in learning and memory: The role of steroid hormones and neurotrophin expression in hippocampus
Description
This work consisted of three parts. In part I the performance of young and old Fisher 344xBrown Norway F1 hybrid rats was tracked in three mazes that are commonly used to detect age-related cognitive decline. In addition to testing whether aged rats of this strain showed deficits in these mazes, behavioral studies also evaluated how similar the mazes were in detecting age-related deficits, and the degree to which physical infirmities biased performance in each of the three mazes. After behavioral tests were complete, animals were killed to evaluate age-related changes in hippocampal morphology and neurotrophin gene expression. Correlations between histology, gene expression, and behavior were examined to discover how performance in each of the mazes reflected age-related changes in the hippocampus In part II changes in cognitive function were monitored in rats that were treated for three months with stress-equivalent concentrations of glucocorticoids. The behavior of glucocorticoid-treated animals was monitored in the same three mazes used in part I. Data were analyzed in order to discover whether glucocorticoid-induced behavioral deficits were specific to particular mazes, and whether the same physical biases that influence aged animals in these mazes also affect glucocorticoid-treated animals In part III, the spatial memory abilities were observed in orchidectomized and intact rats that received glucocorticoid injections or vehicle for thirty days. Animals were tested every six days in the radial arm maze in order to determine if and when behavioral alterations occurred, and whether castration had a significant effect on the incidence and extent of the behavioral alterations. Animals were also tested after glucocorticoid injections had stopped to see how important the active presence of glucocorticoids were to behavioral alterations, and whether castration affected the pattern of behavior after glucocorticoid withdrawal