Development of GLAST(+) Astrocytes and NG2(+) Glia in Rat Hippocampus CA1: Mature Astrocytes Are Electrophysiologically Passive

Glia show marked heterogeneity in terms of electrophysiology in the developing brain, and two major types can be identified based on GFAP or NG2 expression. However, it remains to be determined if such an electrophysiological diversity holds for the adult brain and how GFAP and NG2 lineage glia are associated with different electrophysiological phenotypes during the course of development. To address these fundamental questions, we performed in situ whole cell recording from morphologically identified glia from the rat hippocampal CA1 region from postnatal (P) days 1–106 and double-stained postrecorded cells with GLAST and NG2 antibodies. We found glia express mostly voltage-gated outward K+ currents and also have inward Na+ currents in the newborn (P1–P3), but these are no longer present after P22. They consist equally of GLAST(+) and NG2(+) cells in the newborn, but are mainly NG2(+) in juvenile animals (P4–P21). Glia showing voltage-gated outward and inward K+ currents are also present at P1, peak at P5...