We trained and tested young (6-8months; n=13), middle-aged (12-14months; n=41), and aged (22-24months; n=24) male Fischer 344 rats in a rapid acquisition water maze task and then quantified 27 stress hormones, cytokines and chemokines in their serum, hippocampi and frontal cortices using bead assay kits and xMAP technology. Middle-aged and aged rats learned the location of the hidden platform over training trials more slowly than their young counterparts. After training, young rats outperformed middle-aged and aged rats on both immediate and 24h retention probe trials and about half of the middle-aged and aged (aging) rats exhibited impaired performances when tested on the retention probe trial 24h later. The concentrations of many serum, hippocampal and cortical analytes changed with age often in networks that may represent age-sensitive signaling pathways and the concentrations of some of these analytes correlated with water maze learning and/or memory scores. Serum GRO/KC and RANTES levels, hippocampal GM-CSF levels and cortical IL-9 and RANTES levels were significantly higher in rats categorized as memory-impaired versus elite agers based upon their 24h probe trial performances. Our data add to the emerging picture of how age-related changes in immune and neuroimmune system signaling impacts cognition.
Keywords: Aging; Chemokines; Cytokines; Hippocampus; Inflammation; Memory; Neuroinflammation; Water maze; xMAP technology.
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