Adrenalectomy increases neurogenesis but not PSA-NCAM expression in aged dentate gyrus

Ageing is accompanied by a decline in neurogenesis and in polysialylated is oforms of neural cell adhesion molecule (PSA-NCAM) expression within the hi ppocampus and by elevated basal levels of circulating corticosterone. In a companion study, we demonstrated that suppression of corticosterone by adre nalectomy increased neurogenesis and PSA-NCAM expression in the dentate gyr us of adult rats. Here we show that adrenalectomy increased neurogenesis in this structure in old rats, as measured by the incorporation of 5-bromo-2' -deoxyuridine in neuronal progenitors. This effect was prevented by cortico sterone replacement. In contrast, PSA-NCAM expression remained unchanged in comparison with controls. Thus, in the aged brain, stem cells are still pr esent and able to enter the cell cycle. This may point to ways of protectin g or treating age-related cognitive impairments.