부산대학교 도서관

Abstract Resting membrane potential (RMP), K+ channel contribution to RMP and the development of excitability were investigated in the entire population of acutely dissociated embryonic (E) rat cortical cells over E11–22 using a voltage-sensitive fluorescent indicator dye and flow cytometry. During the period of intense proliferation (E11–13), two cell subpopulations with distinct estimated RMPs were recorded: one polarized at ∼–70 mV and the other relatively less-polarized at ∼–40 mV. Ca2+ o was critical in sustaining the RMP of the majority of less-polarized cells, while the well-polarized cells were characterized by membrane potentials exhibiting a ∼Nernstian relationship between RMP and [K+ ]o . Analysis of these two subpopulations revealed that > 80% of less-polarized cells were proliferative, while > 90% of well-polarized cells were postmitotic. Throughout embryonic development, the disappearance of Ca2+ o -sensitive, less-polarized cells correlated with the disappearance of the proliferating population, while the appearance of the K+ o -sensitive, well-polarized population correlated with the appearance of terminally postmitotic neurons, immuno-identified as BrdU– , tetanus toxin+ cells. Differentiating neurons were estimated to contain increased K+ i relative to less-polarized cells, coinciding with the developmental expression of Cs+ /Ba2+ -sensitive and Ca2+ -dependent K+ channels. Both K+ channels contributed to the RMP of well-polarized cells, which became more negative toward the end of neurogenesis. Depolarizing effects of veratridine, first observed at E11, progressively changed from Ca2+ o -dependent and tetrodotoxin-insensitive to Na+ o -dependent... [ABSTRACT FROM AUTHOR]