Stereotypical physiological properties emerge during early neuronal and glial lineage development in the embryonic rat neocortex

Abstract

Surface immunolabeling was used together with membrane potential and/or Ca2+ indicator dyes to characterize physiological properties emerging among precursors, neuroglial progenitors and differentiating neurons during neurogenesis of embryonic rat neocortex. Cells were immunoidentified with tetanus toxin (TnTx), which binds to gangliosides expressed by neurons, and anti-A2B5, which reacts with gangliosides expressed by neuroglial progenitors. Microdissection of the neocortex into ventricular/subventricular zone (VZ/SVZ) and cortical plate/subplate (CP/SP) regions further resolved the TnTx/A2B5-immunoidentified cells into pre- and post-migratory subpopulations. Quantitative immunocytochemistry revealed mainly proliferative (BrdU+) and immature (nestin+) elements among TnTx-A2B5- precursors and TnTx-A2B85+ progenitors in the VZ/SVZ, and the appearance of neuron-specific antigens among post-mitotic TnTx+ subpopulations of the CP/SP. Flow cytometry of acutely prepared cells in suspension and dual-imaging of cells in culture revealed that ionotropic amino acid receptors and metabotropic acetylcholine receptors closely paralleled the emergence of voltage-dependent Na+ and Ca2+ channels and Na+-Ca2+ exchange activity among TnTx+ neuronal progenitors migrating from VZ/SVZ to CP/SP. During this period, TnTx-A2B5- precursors and TnTx-A2B5+ neuroglial progenitors from VZ/SVZ predominantly exhibited Ca2+ responses to ATP. Thus, stereotypical and contrasting physiologies emerge among embryonic cortical cells in vivo as they initially progress from proliferating precursors and progenitors along neuronal and glial cell lineages.