Immunolocalization of CaMKII and NR2B in hippocampal subregions of rat during postnatal development

Although the expression of CaMKII and synaptic-associated proteins has been widely studied, the temporospatial distribution of CaMKII and NMDAR subunits in different hippocampal subregions during postnatal development still lacks detailed information. In this study, we used immunofluorescent staining to assess CaMKII and NR2B expressions and the relationship between them in CA1, CA3, and DG of rat hippocampus on postnatal (P) days: P0, P4, P7, P10, P14, P21, P28, and P56. The results showed that from P0 to P56, CaMKII expression increased gradually, while NR2B expression decreased gradually, and the time points of their expression peak differed in CA1, CA3, and DG during postnatal development. Although the expression of CaMKII was negatively correlated with NR2B in CA1 and DG, the coexpression of CaMKII with NR2B existed in CA1, CA3, and DG during postnatal development. Interestingly, after P21, CaMKII expression and the coexpression of CaMKII with NR2B became obvious in the Stratum lucidum of CA3. The specific temporospatial distribution pattern of CaMKII with NR2B might be related to the different physiological functions during postnatal development. Discovery of the alteration of the relationship between expression of CaMKII and NMDAR subunits may be helpful for understanding mechanisms and therapy of neurodegenerative diseases.