AMPA-kainate subtypes of glutamate receptor in rat cerebral microglia.
Microglial cells were isolated from rat cerebral cortex, and kainate (KA)-induced inward current was measured at a holding potential of -40 or -60 mV. 6-Cyano-7-nitroquinoxaline-2, 3-dione-sensitive KA-induced currents increased with increasing KA concentration. The half-activation concentration and Hill coefficient were 3.3 x 10(-4) M and 1.4, respectively. Although glutamate (Glu) and AMPA-induced currents were much smaller than that induced by KA, all KA-, Glu-, and AMPA-induced currents were greatly and consistently enhanced in the presence of cyclothiazide (CTZ). On the other hand, KA-induced currents were much less sensitive to potentiation by concanavain A, suggesting that the KA-induced response in rat microglia is predominantly mediated by AMPA-preferring receptors (subunits GluR1-GluR4). The current-voltage relationships of KA- and AMPA-CTZ-induced currents were almost linear or slightly outward rectifying. The reversal potential of KA-induced current shifted to negative potentials (from +4 to -40 mV) on switching from high Na(+) to high Ca(2+) external solution, indicating the low Ca(2+) permeability through the AMPA-KA receptor channel complexes. AMPA-KA receptor expression was studied with immunohistochemistry and reverse transcription-PCR, from which GluR2, GluR3, GluR4, and GluR5 were identified. Lower levels of mRNAs for GluR7 and KA-1-KA-2 were also indicated. Finally, activation of these receptors with KA or Glu significantly enhanced the production of tumor necrosis factor-alpha. These results suggest that primary cultured rat microglia possesses functional Glu receptor, which may mediate neuron to microglia communication in the physiological and pathological states.
Noda
M
M
Laboratory of Cellular and System Physiology, Graduate School of Medical Science, Kyushu University, Fukuoka 812-8582, Japan.
Nakanishi
H
H
Nabekura
J
J
Akaike
N
N
D000818:Animals; D000959:Antihypertensive Agents / Q000494:pharmacology; D001581:Benzothiadiazines / Q000494:pharmacology; D002118:Calcium / Q000493:pharmacokinetics; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D003208:Concanavalin A / Q000494:pharmacology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000494:pharmacology; D007608:Kainic Acid / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D017628:Microglia / Q000737:chemistry* / Q000166:cytology / Q000502:physiology; D018408:Patch-Clamp Techniques; D051381:Rats; D017208:Rats, Wistar; D018091:Receptors, AMPA / Q000032:analysis* / Q000235:genetics; D018092:Kainic Acid Receptors / Q000032:analysis* / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013268:Stimulation, Chemical; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000494:pharmacology
D000959:Antihypertensive Agents; D001581:Benzothiadiazines; D002118:Calcium; D003208:Concanavalin A; D018690:Excitatory Amino Acid Agonists; D018698:Glutamic Acid; D007608:Kainic Acid; D018091:Receptors, AMPA; D018092:Kainic Acid Receptors; D014409:Tumor Necrosis Factor-alpha; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; C004639:cyclothiazide