title: Developmental variation of the permeability to Ca2+ of AMPA receptors in presumed hilar glial precursor cells.
abstract: Glial cells in the hilus of the dentate gyrus of the rat were investigated using the patch-clamp technique in acute slices of the hippocampal formation. According to their voltage-gated current patterns, two classes of glial cells--putative astrocytes and presumed glial precursor cells--were apparent. The glutamate receptor agonists kainate, glutamate, and alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) evoked inward currents at a holding potential of -70 mV in astrocytes and presumed glial precursor cells. Inward currents could also be induced in nucleated patches, indicating a direct action on glial receptors. In presumed hilar glial precursor cells, 6,7-dinitroquinoxaline-2,3-dione (DNQX; 10 microM) blocked the kainate-induced current, while it was partially inhibited by Zn2+ (2 mM) and Evans Blue (10 microM). Cyclothiazide (100 microM), in contrast, potentiated this current, indicating the presence of AMPA receptors. In 90% of the presumed glial precursor cells the excitatory amino-acid-evoked current voltage (I/V) relations were linear or outwardly rectifying and reversed close to 0 mV, which is characteristic for non-specific cation channels. To determine the permeability to Ca2+, I/V relations were determined in a Na(+)-free solution containing 40 mM Ca2+ and showed reversal potentials of a wide variation ranging from -63 mV to +1 mV with corresponding PCa/PCs permeability ratios of between 0.09 and 2.10. Statistical analysis revealed that the permeability to Ca2+ significantly decreased with an advance in age (r = -0.596; n = 21; P < 0.01). These data suggest that the Ca2+ influx mediated by the activation of AMPA receptors expressed in presumed hilar glial precursor cells is dependent on the developmental stage.
authors.affiliation: Department of General Zoology, University of Kaiserslautern, Germany.
authors.forename: K H
authors.initials: KH
authors.lastname: Backus
authors.forename: T
authors.initials: T
authors.lastname: Berger
mesh_terms: D000818:Animals; D015220:Calcium Channels / Q000378:metabolism*; D018891:Dentate Gyrus / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism*; D015536:Down-Regulation / Q000187:drug effects; D004594:Electrophysiology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D066298:In Vitro Techniques; D015640:Ion Channel Gating / Q000187:drug effects; D009457:Neuroglia / Q000378:metabolism*; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000378:metabolism; D051381:Rats; D018091:Receptors, AMPA / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015222:Sodium Channels / Q000378:metabolism; D013234:Stem Cells / Q000378:metabolism; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000494:pharmacology
chemical_list: D015220:Calcium Channels; D018690:Excitatory Amino Acid Agonists; D015221:Potassium Channels; D018091:Receptors, AMPA; D015222:Sodium Channels; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid