Development of resting membrane potentials of embryonic murine spinal cord cells evaluated by flow cytometric analysis.

The membrane electrical properties of embryonic murine spinal cord cells of embryonic day-10 (E10) to E14 were studied using a voltage-sensitive oxonol dye combined with fluorescence-activated cell sorting techniques. This period of development corresponds to the time when neurons differentiate from their neuroblast precursors. Bovine oligodendrocytes were also investigated in these studies as they have an exclusive K+ dependence on resting membrane potential (RMP). Fluorescence emission histograms of spinal cord cells on E11-E14 exhibited little difference, suggesting that the RMP of cells of these ages were similar. Applications of Leiuris toxin, batrachotoxin, veratrine and veratridine, which modify sodium channel gating, produced shifts in the fluorescence histograms of cells on E12, E13 and E14 indicating membrane depolarization. The results indicated that RMP of spinal cord cells do not change appreciably between E11 and E14 and that the initial appearance of a voltage-dependent Na+ conductance occurs at E12.