Developmental changes in distribution of NMDA receptor channel subunit mRNAs.

In situ hybridization analyses have revealed drastic changes in expression and distribution of five subunit mRNAs of the mouse NMDA receptor channel during brain development. The epsilon 1 subunit mRNA is expressed postnatally and widely in the brain. On the other hand, the epsilon 2 subunit mRNA is found throughout the entire embryonic brain, but its expression becomes restricted to the forebrain at postnatal stages. The epsilon 3 subunit mRNA appears postnatally and predominantly in the cerebellum, whereas the epsilon 4 subunit mRNA is abundantly expressed in the diencephalon and the brainstem at embryonic and neonatal stages. In contrast, the zeta 1 subunit mRNA distributes ubiquitously in the brain throughout development. These findings suggest that changes in the subunit composition of the NMDA receptor channel take place during brain development.