Developmental regulation of voltage-activated Na+ and Ca2+ currents in rat retinal ganglion cells

THE developmental regulation of voltage-gated Na+ and Ca2+ current expression was investigated in rat retinal ganglion cells (RGCs) using whole cell patch clamp recordings. Experiments were performed on retinal whole mounts and slices from embryonic day 14 (E14), the developmental stage where RGCs start to differentiate from their precursor cells, to postnatal day 25 (P25) where the retina is fully differentiated and the animals have opened their eyes. No voltage-activated ion currents could be detected earlier than E17. From E17/18 on, small voltage-gated Na+ and Ca2+ currents could be measured which increased remarkably in amplitude until P16. Analysis of current kinetics and application of specific calcium channel antagonists revealed an alteration in the contribution of different Ca2+ current components to the voltage-activated wholecell Ca2+ current in RGCs during development.