Dexamethasone Reduces Cytokine mRNA Levels and Microglial Activity in the Brainstem of Newborn Rats

During the perinatal period of ontogeny, microglia performs functions of a critical key-regulator of the angio-, neuro-, and synaptogenesis processes. Under normal development, without inflammation induction, administration of the glucocorticoid hormone dexamethasone (0.2 mg/kg) caused a rapid decrease in the mRNA levels of both pro- and anti-inflammatory cytokines in the brainstem of neonatal rat pups. A decrease in the expression of the Il1b and Tnfa genes was observed within 1 h, and Il10 and Tgfb1, 4 h after the administration of the hormone to 3-day-old rat pups. Suppression of cytokine mRNA levels was accompanied by a decrease in the number of cells expressing the microglia marker protein IBA1 in the locus coeruleus region of the brainstem in 6 h after glucocorticoid administration. The identified features of the dexamethasone action can weaken the participation of microglia in the processes of neuroplasticity in the developing brain, which may be one of the reasons for long-term changes in brain functioning.