Quantitative comparison of mRNA densities for NMDA subunits within brain regions of different ages of mice. Densities (counts per minute per milligram of tissue) of mRNA for the ζ1 (A, B), ε1 (C, D), and ε2 (E, F) subunits of the NMDA receptor in different cortical (A, C, E) and hippocampal and subcortical (B, D, F) regions in 3-, 10-, and 30-month-old mice. * indicates p < 0.05 for difference from 3-month-old mice. # indicates p < 0.05 for difference from 10-month-old mice. A–D,n = 12 for 3 and 10 month olds, n = 13 for 30 month olds.E, F,n = 11 for 3 month olds, 12 for 10 month olds, and 10 for 30 month olds. in, Cortical layers IV–VI; out, cortical layers II–III;Fron, frontal; Par, parietal;O/T, occipital/temporal; Ento, entorhinal; pyr, pyramidal cell layer;DGL, dentate granule cell layer; dors, dorsal blade; vent, ventral blade;Cerebell, cerebellum.