Objective

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To identify areas of NG2 cells and astrocytes

Objective

To examine whether the neuron‐NG2 cell

synapses have adequate LTP components

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Hippocampal slice preparation

• Rats (P14 ‐ 17 days) were anaesthetized with

sodium pentobarbital.

• Decapitation ==> removed the brain

• Transverse slices (400 μmthick) were cut with

a vibratome

• Slices were visualized with infrared optics

using an upright microscope equipped with

DIC optics.

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Electrophysiology

• Whole‐cell patch recordings were made from glial

cells in SR cells in SR

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Electrophysiology

• Field EPSPs were recorded from the dendrites of CA1

pyramidal cells.

• 30‐40% of the maximum response.

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Calcium fluorescence imaging

• Oregon Green 488 BAPTA‐1 or Rhod‐2

• After obtaining the whole‐cell configuration, 15 min

were allowed for intracellular diffusion of the dyes.

• Imaging was performed using a two‐photon confocal

laser scanning microscope

• Relative changes in fluorescence (ΔF/F)

• Calcium elevation in NG2 cells was evoked by local

application of glutamate via a microtube .

• TTX , bicuculline, APV, nifedipine, and CTZ .

• In some experiments, SC stimulation‐induced Ca 2+

elevation

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large transient A‐type currents (I A ) and

delayed rectifier K + currents (I K )

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small tetrodotoxin (TTX)–sensitive Na + currents

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no detectable voltage‐dependent Ca 2+ currents

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• rise time, 0.71 ±0.06 ms;

•decay time, 2.13 ± 0.17 ms;

•N=11

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The EPSCs exhibited short‐term plasticity similar to

The EPSCs exhibited short‐term plasticity similar to

that induced at neuronal synapses


NG2 cell properties

• NG2 cells and astrocytes revealed two distinct

nonoverlapping cell populations

• A relatively high input resistance

• Large transient A‐type currents (I A )

• Small tetrodotoxin (TTX)–sensitive Na + currents

• No detectable voltage‐dependent Ca 2+ currents

• Electrical stimulation of SCs elicited inward currents

• Exhibited short‐term plasticity

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Glutamate

• Glutamate is the most abundant fast excitatory

neurotransmitter in the mammalian nervous system.

• Nerve impulses trigger release of glutamate from the

pre‐synaptic cell.

•There are two basic types of neural receptors:

ionotropic, and metabotropic.

Type

ionotropic

ionotropic

ionotropic

metabotropic

Name

NMDA receptor

Kainate receptor

AMPA receptor

mGluR

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• APV, the NMDARs antagonist

• PhTx, a specific blocker of CaPARs

• Kynurenic acid (Kyn), a broad‐spectrum blocker of

ionotropic glutamate receptors

• DNQX, the antagonist of non‐NMDARs

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• APV, the NMDARs antagonist

• DNQX, the antagonist of non‐NMDARs

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Calcium fluorescence imaging

• glutamate‐induced currents and Ca 2+ elevations were largely

abolished by DNQX (non‐ NMDAR antagonist)

• significantly reduced by NAS (CaPAR blocker)

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NG2 cells show Ca 2+ permeable AMPAR current

• PhTx, a specific blocker of CaPARs

• DNQX, the antagonist of non‐NMDARs

• APV, the NMDARs antagonist

• Kynurenic acid (Kyn), a broad‐spectrum blocker of

ionotropic glutamate receptors

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Glia‐ LTPs and Blockers

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TBS VS Tetanic

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Example EPSC recordings from an NG2 cell

showing similar PPR recorded before and after

TBS application

No presynaptic p change in glutamate release probability

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Summary of the rectification of EPSCs examined

before and after TBS induction in NG2 cells

loaded with or without spermine

TBS induced an increased rectification of EPSCs

Loading NG2 cells with spermine caused more rectification

of SC‐induced EPSCs

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• The conversion of CaPARs into Ca 2+ impermeable

receptors at Bergmann glial cells , results in the

retraction of glial processes that ensheath

synapses and multiple innervations of Purkinje

cells by climbing fibers.

(Iino M et al.,2001)

• Ischemia also down‐regulate GluR2 expression in

OPCs and neurons,leading to the expression of

CaPARs and enhanced glutamate toxicity after

ischemia.

(Pellegrini‐Giampietro D E et al.,1997)

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• Thus, an adequate level of activity by CaPARs is

important for maintaining normal synaptic

structure and function.

• Glutamate receptor activation is linked to the

proliferation i and differentiation i i of OPCs.

(Gallo V et al.,1996)

• NG2 cells can differentiate into neurons both in

vitro and in vivo.

(Nunes M C et al.,2003 ; Aguirre A et al.,2004)

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• Like astrocytes, NG2 cells may also secrete

neuroactive factors to regulate neuronal

functions.

• Rapid neuron‐NG2 cell signaling may allow rapid

feedback regulation of neuronal functions by

Ca 2+ ‐dependent secretion of neuroactive factors,

• The strength of such feedback regulation will

increase after the induction of gLTP.

(Yang Y et al.,2003 ; Zhang J M et al.,2003 ; Araque A et al.,2001 )

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Conclusion

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