title: AMPA-type glutamate receptors in glial precursor cells of the rat corpus callosum: ionic and pharmacological properties.
abstract: Glial cells in fiber tracts express various functional transmitter receptors, e.g., got glutamate. However, little is known about their biophysical and pharmacological profile. Using the in situ patch-clamp technique, kainate- and AMPA-induced conductance changes of glial precursor cells in the rat corpus callosum were investigated to study these aspects. Precursor cells were identified by their voltage-gated currents and were easily discernable from astrocytes and oligodendrocytes. Kainate induced two overlying effects in these cells: the activation of a cationic current and the block of potassium conductances. Cesium in the pipette solution blocked potassium conductances nearly completely and the ionic profile of the kainate-induced cationic current could be studied in detail. Full replacement of the sodium in the bath by calcium resulted only in a small kainate-induced (calcium) inward current flow, but the kainate-induced outward current carried by Cs+ was less affected reflecting a weak calcium permeability. The kainate response could be blocked by 6,7-dinitroquinoxaline-2,3-dione (DNQX) and millimolar zinc concentrations. Co-application of micromolar concentrations of zinc slightly enhanced the kainate-induced current, while Evans Blue was without any significant effect. Cyclothiazide increased the kainate response by a factor of x6 while concanavalin A did not enlarge it. The AMPA-induced current was amplified by a factor of x39 by cyclothiazide. The present data suggested the expression of weakly calcium-permeable AMPA receptors on glial precursor cells in the rat corpus callosum. Only a small fraction of the agonist-induced current could be seen without the appropriate blockers of receptor desensitization. An additional expression of kainate-preferring glutamate receptors could not be shown.
authors.affiliation: Institute of Anatomy, University of Freiburg, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Berger
mesh_terms: D000818:Animals; D001581:Benzothiadiazines / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002712:Chlorides / Q000494:pharmacology; D003208:Concanavalin A / Q000494:pharmacology; D003337:Corpus Callosum / Q000166:cytology*; D004232:Diuretics; D005070:Evans Blue / Q000494:pharmacology; D007608:Kainic Acid / Q000494:pharmacology; D009457:Neuroglia / Q000378:metabolism* / Q000648:ultrastructure; D018408:Patch-Clamp Techniques; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D018091:Receptors, AMPA / Q000502:physiology*; D018092:Kainic Acid Receptors / Q000502:physiology; D049993:Sodium Chloride Symporter Inhibitors / Q000494:pharmacology; D017967:Zinc Compounds / Q000494:pharmacology
chemical_list: D001581:Benzothiadiazines; D002118:Calcium; D002712:Chlorides; D003208:Concanavalin A; D004232:Diuretics; D005070:Evans Blue; D007608:Kainic Acid; D011810:Quinoxalines; D018091:Receptors, AMPA; D018092:Kainic Acid Receptors; D049993:Sodium Chloride Symporter Inhibitors; D017967:Zinc Compounds; C056723:FG 9041; C016837:zinc chloride; C004639:cyclothiazide