Entorhinal cortex lesions transiently alter glucocorticoid but not mineralocorticoid receptor gene expression in the rat hippocampus

Individual differences in hypothalamic-pituitary-adrenal activity in later life and hippocampal aging

Variation in magnitude of cognitive decline in later life is a central feature of human aging. The more severe forms of dementias, such as Alzheimer's disease, clearly define one end of the spectrum. However, among those showing no obvious signs of clinical dementia there are considerable individual differences. Thus, although evidence for learning, memory, and language loss appears in some individuals as early as 50-55 years of age, many people continue to function alertly well into their 90s. These individuals exemplify what Rowe and Kahn (1987) have termed "successful" aging. The wide variability in CNS aging, often a nuisance factor in studies, are becoming a major focus for brain aging research (e.g., Gage et al., 1984;Gallager and Pelleymounter, 1988; Aitken and Meaney, 1990; Issa et al., 1990). Our studies over the past few years have added support to the idea that individual differences in hypothalamic-pituitary-adrenal (HPA) activity can account for part of the variation seen in neurological function among the elderly. In this article we discuss the evidence for the idea that adrenal glucocorticoids can compromise hippocampal function and, thus, produce cognitive impairments, as well as the potential mechanisms for these effects.

Transcription factor AP-2 gene expression in adult rat hippocampal regions: effects of environmental manipulations

Environmental enrichment increases glucocorticoid receptor expression in hippocampal pyramidal neurons, but the molecular mechanisms are unknown. Several transcription factors are expressed in hippocampal neurons where they respond to environmental stimuli. In this study 12 adult male rats (n = 6 in each group) were exposed to enriched or isolated environment for 30 days. The expression of AP-2 mRNA, studied by in situ hybridization, was attenuated by environmental enrichment in the CA2 and CA3 subfields of the hippocampus. AP-2 may be involved in the environmental effect of glucocorticoid receptor gene expression in these neurons.