Potentiation of NMDA receptor-mediated synaptic responses by microglia.
To study the influence of microglia on glutamatergic synaptic transmission in the acute phase of neuronal injury, we first examined the effects of primary cultured microglia transferred onto the organotypic cortical slice cultures. In these microglia-transferred cortical slice cultures, stimulation of the subcortical white matter induced fast excitatory postsynaptic potentials followed by N-methyl-D-aspartate (NMDA) receptor-mediated plateau-like potentials that were never observed in control slice cultures. A similar potentiation of NMDA receptor-mediated postsynaptic responses was also observed by an application of a microglial-conditioned medium (MCM, 10% v/v) in acute cortical slices. These effects of MCM disappeared after boiling or incubation with proteinase K. After fractionation of MCM by anion-exchange chromatography, the enhancing activity of each fraction was quantitated electrophysiologically. When each fraction was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the fraction 24 which showed the most potent enhancing activity on NMDA receptor-mediated responses contained a relatively strong protein band with a molecular mass of approximately 70 kDa. MCM also enhanced both glutamate- and NMDA-induced inward currents recorded from acutely isolated cortical neurons. It was also noted that glutamate and NMDA induced transient large inward currents during an application of MCM, which were never observed in the control condition. These observations strongly suggest that NMDA receptor-mediated responses can be potentiated by both heat- and protease-labile (presumably 70-kDa proteins) molecules released from microglia.
Moriguchi
Shigeki
S
Laboratory of Oral Aging Science, Faculty of Dental Sciences, Kyushu University, Maidashi 3-1-1, Fukuoka 812-8582, Japan.
Mizoguchi
Yoshito
Y
Tomimatsu
Yoshiro
Y
Hayashi
Yoshinori
Y
Kadowaki
Tomoko
T
Kagamiishi
Yoshifumi
Y
Katsube
Nobuo
N
Yamamoto
Kenji
K
Inoue
Kazuhide
K
Watanabe
Shigenori
S
Nabekura
Junichi
J
Nakanishi
Hiroshi
H
D000818:Animals; D000831:Animals, Newborn; D001921:Brain / Q000378:metabolism* / Q000503:physiopathology; D001930:Brain Injuries / Q000378:metabolism / Q000503:physiopathology; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000494:pharmacology; D004558:Electric Stimulation; D004660:Encephalitis / Q000378:metabolism / Q000503:physiopathology; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology; D018698:Glutamic Acid / Q000378:metabolism / Q000494:pharmacology; D008297:Male; D017628:Microglia / Q000378:metabolism* / Q000637:transplantation; D008970:Molecular Weight; D016202:N-Methylaspartate / Q000494:pharmacology; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009924:Organ Culture Techniques; D017729:Presynaptic Terminals / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D018091:Receptors, AMPA / Q000378:metabolism; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism*; D009435:Synaptic Transmission / Q000502:physiology*
D017077:Culture Media, Conditioned; D009419:Nerve Tissue Proteins; D018091:Receptors, AMPA; D016194:Receptors, N-Methyl-D-Aspartate; D018698:Glutamic Acid; D016202:N-Methylaspartate