Expression of brain G sub(i) protein in the aging F344 rat following exposure to corticosterone

G protein expression has been shown to be modulated by circulating plasma corticosterone in young animals. A loss of G protein expression regulation by corticosterone in the elderly could explain declines in the function of G protein-coupled receptors and their effective signal transduction processes in the nervous system found in normal and pathological aging. In this study, adrenalectomized 3- and 18-months-old female Fischer 344 rats were exposed to low, moderate or high levels of plasma corticosterone to determine the effect of this hormone on G sub(i) protein expression in the hippocampus and frontal cortex. Basal G sub(i) protein expression, assessed by Western blot analysis, did not vary across age in either brain region. Hippocampal G sub(i) protein levels increased following moderate and high corticosterone administration in the 3-months old animals (125%; P < 0.05) but not in the 18-months old animals. In contrast, in the frontal cortex, G sub(i) protein expression increased significantly in the 18-months-old group (93%; P < 0.05) following exposure to high concentrations of corticosterone. These results suggest that steroid hormones, specifically corticosterone, may differentially modulate neurotransmitter-G protein coupling in an age-dependent manner.