ON THE ROLE OF GLUCOCORTICOID RECEPTORS IN BRAIN PLASTICITY

1. The mapping of glucocorticoid receptors (GR) in the rat central ner vous system (CNS) has demonstrated their widespread presence in large numbers of nerve and glial cell populations also outside the classical stress regions. 2. The present paper summarizes the evidence that glu cocorticoids via GR in the CNS can act as lifelong organizing signals from development to aging. The following examples are given, (a) In th e prepubertal and adult offspring, prenatal corticosterone treatment c an produce long-lasting changes in striatal dopaminergic communication , (b) In adulthood, the evidence suggests complex regulation by adreno cortical hormones of neurotrophic factors and their receptors in the h ippocampal formation. (c) In aging, the strongly GR-immunoreactive pyr amidal cell layer of the CA1 hippocampal area appears to be preferenti ally vulnerable to neurotoxic actions of glucocorticoids, especially i n some rat strains.3. Strong evidence suggests that each nerve cell in the CNS is supported by a trophic unit, consisting of other nerve cel ls and filial cells, blood vessels, and extracellular matrix molecules , Due to multiple actions on nerve and glial cell populations of the d ifferent trophic units, the glucocorticoids may exert either an overal l trophic or a neurotoxic action. It seems likely that with increasing age, the endangering actions of glucocorticoids on nerve cells prevai l over the neurotrophic ones, leading to reduced nerve cell survival i n some trophic units.