Glucocorticoid Receptor Expression in the Different Cell Types of the Neonatal Rat Hippocampus and Cortex

Glucocorticoids (GCs) are crucial regulators of organism homeostasis and function. Despite severe consequences, glucocorticoid therapy in neonates is widely used antenataly for accelerating fetal lung maturation in cases of preterm birth. GC action is mediated by glucocorticoid receptors, ligand-activated transcription factors. Despite broad range of information concerning GR expression in the brain, not so much known about GR expression in the neonatal brain in aspects of cell specificity and identity. In this work, we performed comparative study of GR expression together with panel of main neuronal and astrocytic cell markers in the neonatal rat brain. We immunohistochemically studied GR expression in the hippocampal CA1 field and entorhinal cortex together with cortical projection neuron markers Satb2 and Nurr1, interneuron marker calretinin, and astrocytic marker GFAP. The highest colocalization coefficients were observed for GR with calretinin. With projection neuron markers, which are also transcription factors, colocalization coefficients increased to the same values as for GR-calretinin 6h after dexamethasone injection and GR were translocated to the nucleus. Our analysis showed that in the neonatal rat brain GR are more localized in neurons than in astrocytes.