title: Electrophysiologically "complex" glial cells freshly isolated from the hippocampus are immunopositive for the chondroitin sulfate proteoglycan NG2.
abstract: We have recently described a subgroup of isolated glial fibrillary acidic protein-positive (GFAP+) hippocampal astrocytes that predominantly express outwardly rectifying currents (which we term "ORAs" for outwardly rectifying astrocytes), which are similar to the currents already described for hippocampal GFAP- "complex glia." We now report that post-recording staining of cells that were first selected as "complex" by morphology and then confirmed by their electrophysiological characteristics were NG2+ approximately 90% of the time. Also, the morphology of freshly isolated NG2+ cells differs from that of isolated GFAP+ ORAs in having a smaller and round cell body with thinner processes, which usually are collapsed back onto the soma. Upon detailed examination, NG2+ cells were found to differ quantitatively in some electrophysiological characteristics from GFAP+ ORAs. The outward, transient K+ currents (IKa) in the NG2+ cells showed a slower decay than the IKa in ORAs, and their density decreased in NG2+ cells from older animals. The other two major cation currents, the voltage-activated Na+ and outwardly delayed rectifier K+ currents, were similar in NG2+ cells and ORAs. To further distinguish isolated complex cells from outwardly rectifying GFAP+ astrocytes, we performed immunocytochemistry for glial markers in fixed, freshly isolated rat hippocampal glia. NG2+ cells were negative for GFAP and also for the astrocytic glutamate transporters GLT-1 and GLAST. Thus the isolated hippocampal NG2+ glial cells, though having an electrophysiological phenotype similar to that of ORAs, are an immunologically and morphologically distinct glial cell population and most likely represent NG2+ cells in situ.
authors.affiliation: Center for Neuropharmacology and Neuroscience, Albany Medical College, Albany, New York 12208, USA.
authors.forename: Gary P
authors.initials: GP
authors.lastname: Schools
authors.forename: Min
authors.initials: M
authors.lastname: Zhou
authors.forename: Harold K
authors.initials: HK
authors.lastname: Kimelberg
mesh_terms: D027322:Amino Acid Transport System X-AG / Q000378:metabolism; D000779:Anesthetics, Local / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D000941:Antigens / Q000032:analysis* / Q000276:immunology; D002452:Cell Count; D002478:Cells, Cultured; D004553:Electric Conductivity; D005904:Glial Fibrillary Acidic Protein / Q000276:immunology; D006624:Hippocampus / Q000166:cytology* / Q000378:metabolism; D007150:Immunohistochemistry / Q000379:methods; D009457:Neuroglia / Q000145:classification / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D018408:Patch-Clamp Techniques / Q000379:methods*; D011509:Proteoglycans / Q000032:analysis* / Q000276:immunology; D051381:Rats; D013779:Tetrodotoxin / Q000494:pharmacology; D013997:Time Factors; D000099216:Chondroitin Sulfate Proteoglycan 4
chemical_list: D027322:Amino Acid Transport System X-AG; D000779:Anesthetics, Local; D000941:Antigens; D005904:Glial Fibrillary Acidic Protein; D011509:Proteoglycans; D013779:Tetrodotoxin; D000099216:Chondroitin Sulfate Proteoglycan 4