THE DEVELOPMENT OF NEURAL VISININ-LIKE CA2-BINDING PROTEIN-2 IMMUNOREACTIVITY IN THE RAT NEOCORTEX AND HIPPOCAMPUS()

Neural visinin-like Ca2+-binding protein 2 (NVP2) immunoreactivity in the rat neocortex and hippocampus was barely detectable by immunoblot analysis on postnatal day 1 (P1), but increased during postnatal weeks 2-3, reaching a plateau on P28. Immunohistochemical analysis revealed moderate immunoreactivity firstly on P7 in some subsets of the hippoc ampal interneurons and in the hippocampal pyramidal cells and dentate granule cells. Immunoreactivity of the interneurons decreased during p ostnatal weeks 2-3 and disappeared by P28. In contrast, immunoreactivi ty of the cortical and hippocampal pyramidal cells and dentate granule cells abruptly increased during postnatal week 2. The distinctly immu noreactive cells were distributed throughout the neocortex, especially in the cortical plate, and the stratum pyramidale of Ammon's horn and granular layer of the dentate gyrus on P14. Immunoreactivity was homo geneously concentrated in the cell bodies and proximal dendrites at th is stage, whereas thereafter immunoreactivity in the neuropil graduall y increased, and underwent a relative decrease in the cell bodies. By P28, the higher and granular immunoreactivity in the neuropil covered whole layers of the neocortex, Ammon's horn and the dentate gyrus, the same as in adults. Differential expression of NVP2 in different neuro n populations may reflect the differential functional consequences for neuronal development.