Reduced glucocorticoid binding site concentration in cortical neuronal perikarya from senescent rats

Isolated neuronal perikarya from cerebral cortices of senescent (24-26-month-old) male rats exhibit a 55-65% reduction in the concentration of specific cytosol glucocorticoid binding sites when compared to mature counterparts (12-13 months). Neuronal preparations from the two age groups are essentially identical with respect to yield, protein content, physiochemical integrity and purity as judged by enrichment for free glycine and reduction in carbonic anhydrase specific activity (relative to unfractionated cortical cell suspensions). Adrenalectomy does not alter the number of glucocorticoid binding sites in either group, and age differences do not appear due to differential partitioning of sites between nucleus and cytoplasm. It is suggested that loss of receptors from the cortical neuron population represents a possible mechanism by which glucocorticoid responsiveness may be decreased during aging.