The fate of synaptic input to NG2 glial cells: neurons specifically downregulate transmitter release onto differentiating oligodendroglial cells.
NG2-expressing oligodendrocyte precursor cells (OPCs) are ubiquitous and generate oligodendrocytes throughout the young and adult brain. Previous work has shown that virtually every NG2 cell receives synaptic input from many axons, but the meaning of this signaling is not understood. In particular, it is unclear whether neurons specifically synapse onto OPCs or whether OPCs merely trace adjacent neurotransmitter release sites and are not recognized by the presynaptic neuron. Here, we show with whole-cell recordings from distinct developmental stages of oligodendroglial cells in brain slices that synaptic input essentially disappears as soon as OPCs differentiate into premyelinating oligodendrocytes (NG2(-), DM20/PLP(+), O1(+)). Uncaging experiments and tracer loading revealed that premyelinating oligodendrocytes still express a substantial number of AMPA/kainate receptors and many processes, but spontaneous and stimulated synaptic currents are mostly absent. Nevertheless, in a minority of premyelinating cells, electrical stimulation evoked small synaptic currents with an unusual behavior: their amplitude compared well with the quantal amplitude in OPCs but they occurred asynchronously and with the remarkable latency of 40-100 ms, indicating that the presynaptic release machinery has become ineffective. Mature myelinating oligodendrocytes completely lack AMPA/kainate receptors and respond to uncaging and synaptic stimulation with glutamate transporter currents. Our data show that neurons selectively synapse onto only one of several coexisting developmental stages of glial cells and thereby indicate that neurons indeed specifically signal to OPCs and are able to modulate transmitter output by regulating the local release machinery in a manner specific to the developmental stage of the postsynaptic glial cell.
Kukley
Maria
M
Department of Neurosurgery, University Clinic Bonn, D-53105 Bonn, Germany.
Nishiyama
Akiko
A
Dietrich
Dirk
D
D018750:6-Cyano-7-nitroquinoxaline-2,3-dione / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects / Q000235:genetics; D000367:Age Factors; D000818:Animals; D000831:Animals, Newborn; D000941:Antigens / Q000378:metabolism*; D001224:Aspartic Acid / Q000494:pharmacology; D001640:Bicuculline / Q000494:pharmacology; D002454:Cell Differentiation / Q000502:physiology*; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics; D004558:Electric Stimulation / Q000379:methods; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000235:genetics; D018682:GABA Agents / Q000494:pharmacology; D018698:Glutamic Acid / Q000494:pharmacology; D049452:Green Fluorescent Proteins / Q000235:genetics; D006624:Hippocampus / Q000166:cytology* / Q000254:growth & development; D066298:In Vitro Techniques; D051379:Mice; D008822:Mice, Transgenic; D018991:Myelin Proteolipid Protein / Q000235:genetics / Q000378:metabolism; D009474:Neurons / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000378:metabolism*; D009557:Nipecotic Acids / Q000494:pharmacology; D009836:Oligodendroglia / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques / Q000379:methods; D011509:Proteoglycans / Q000378:metabolism*; D013234:Stem Cells / Q000502:physiology; D013569:Synapses / Q000187:drug effects / Q000502:physiology*; D000099216:Chondroitin Sulfate Proteoglycan 4
D018750:6-Cyano-7-nitroquinoxaline-2,3-dione; D000941:Antigens; D001224:Aspartic Acid; D001640:Bicuculline; D018691:Excitatory Amino Acid Antagonists; D018682:GABA Agents; D018698:Glutamic Acid; D049452:Green Fluorescent Proteins; D018991:Myelin Proteolipid Protein; D018377:Neurotransmitter Agents; D009557:Nipecotic Acids; D011509:Proteoglycans; D000099216:Chondroitin Sulfate Proteoglycan 4; C047516:Plp1 protein, mouse; C120673:benzyloxyaspartate; C045598:N-(4,4-diphenyl-3-butenyl)nipecotic acid