Project 2 - Aging is associated with a decline in cognitive performance. PFC shows particularly large functional deterioration with age. The molecular mechanisms responsible for this decline are poorly understood. Our preliminary data suggests that aging is associated with increased cAMP signaling in the PFC. Antagonizing cAMP signaling in the PFC improves working memory performance and increasing cAMP signaling in the PFC causes further declines in working memory. We have also shown that HCN1 and 2 channels are expressed on dendritic spines where cAMP can affect channel opening and reduce the magnitude of synaptic inputs. Aged PFC shows reduced expression of RNA for PDE4A which would be expected to cause increased cAMP levels. Western blots demonstrate increased HCN1 expression in aged PFC. We hypothesize that cAMP levels increase with aging and that the deleterious effects of cAMP are mediated by HCN ion channels. To test this hypothesis we will measure cAMP levels in the prefrontal cortex of young, aging, and aged rats. We will then overexpress PDE4A using viral methods and measure working memory performance. We predict that increasing PDE4A expression to that seen in young animals will improve working memory performance in aged rats. We will then examine the role of HCN channels by overexpressing or knocking down HCN 1/2 expression and measure working memory. We predict that reducing HCN expression will reverse the effects of aging on PFC function and that overexpression will cause further deterioration. We will use cDNA microarrays and protein profiling approaches to examine RNA and protein expression changes associated with aging in the PFC to generate additional hypotheses. Genes identified in this manner will be targeted for overexpression and knockdown studies. We believe that this work will identify components of the cAMP signaling pathway that underlie decreased working memory performance associated with aging. Lay language: Certain cognitive capacities become less efficient with aging. One such capacity known as working memory plays an important role in carrying out tasks associated with daily living and is mediated by the prefrontal cortex. We have determined that age-related changes in cyclic AMP signaling in the prefrontal cortex may cause reduced working memory performance. This proposal seeks to uncover the molecular mechanisms responsible for these changes.
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