Genetic and epigenetic regulation of NMDA receptor expression in the rat visual cortex

The susceptibility of cortical networks to use-dependent modifications decl ines with age (critical period) and this decline of neuronal plasticity dur ing development is paralleled by the shortening of NMDA receptor EPSCs. We showed previously in the somatosensory cortex that the shortening of NMDA r eceptor kinetics correlates with a developmentally-regulated increase in th e NR2A subunit expression. Here we examine whether this developmental regul ation of NR2A expression is related to the duration of critical periods and whether it is influenced by experience. Functional NMDA receptors and thei r molecular characteristics are studied in identified layer IV neurons of r at visual cortex. In this structure the time course of the critical period differs from that in the somatosensory cortex and can be changed by sensory deprivation, thus permitting examination of correlations between the time course of receptor expression and the duration of the critical period. We f ind that the developmental expression of the NR2A subunit is delayed compar ed with the somatosensory cortex, in agreement with the prolonged critical period in the visual cortex. Moreover, sensory deprivation further delays t he developmental change in the NMDA receptor subunit composition, demonstra ting the activity dependence of this process and strengthening the correlat ion between changes in subunit composition and the time course of the criti cal period.