• 생물정신의학
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• 제20권1호
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• pp.1-5
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• 2013

Glutamate receptors are important components of synaptic transmission in the nervous system. Especially, ${\alpha}$-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors mediate most abundant excitatory synaptic transmission in the brain. There is elaborate mechanism of regulation of AMPA receptors including protein synthesis/degradation, intracellular trafficking, exocytosis/endocytosis and protein modification. In recent studies, it is revealed that functional dysregulation of AMPA receptors are related to major psychiatric disorders. In this review, we describe the structure and function of AMPA receptors in the synapse. We will introduce three steps of mechanism involving trafficking of AMPA receptors to neuronal membrane, lateral diffusion into synapses and synaptic retention by membrane proteins and postsynaptic scaffold proteins. Lastly, we will describe recent studies showing that regulation of AMPA receptors is important pathophysiological mechanism in psychiatric disorders.

• Archives of Pharmacal Research
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• 제24권6호
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• pp.613-617
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• 2001

The present study examined the hypothesis that NMDA, AMPA/Kainate, and metabotropic (mGlu) glutamate receptors contribute to a behavioral stimulation induced by activation of dopamine receptors by comparing responses in apomorphine-induced cage climbing behaviors in mice. MK-801, CNQX, and MCPG were served as the NMDA receptor, AMPA/Kainate receptor, and mGlu receptor antagonist, respectively, to elucidate the glutamatergic modulation in apomorphine-induced eopaminergic activation in mice. Drugs were administered intracerebroventricularly (i.c.v.) into the mouse brain 15 min before the apomorphine treatment (2 mg/kg, s.c.). 1.c.v. injection of MK-801 inhibited the apomorphine-induced cage climbing behavior dose-dependently. However, treatments with CNQX and MCPG did not any significant change in apomorphine-induced cage climbing behavior in mice. These results suggest that stimulation of NMDA type of glutamate receptors could contribute to the dopaminergic sti mutation, but not AMPA/Kainate and mGlu type glutamate receptors.

• The Korean Journal of Physiology and Pharmacology
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• 제13권3호
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• pp.209-214
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• 2009

The striatum receives glutamatergic afferents from the cortex and thalamus, and these synaptic transmissions are mediated by ${\alpha}$-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) and N-methyl D-aspartate (NMDA) receptors. The purpose of this study was to characterize glutamate receptors by analyzing NMDA/AMPA ratio and rectification of AMPA and NMDA excitatory postsynaptic currents (EPSCs) using a whole-cell voltage-clamp method in the dorsal striatum. Receptor antagonists were used to isolate receptor or subunit specific EPSC, such as (DL)-2-amino-5-phosphonovaleric acid (APV), an NMDA receptor antagonist, ifenprodil, an NR2B antagonist, CNQX, an AMPA receptor antagonist and IEM-1460, a GluR2-lacking AMPA receptor blocker. AMPA and NMDA EPSCs were recorded at - 70 and + 40 mV, respectively. Rectification index was calculated by current ratio of EPSCs between + 50 and - 50 mV. NMDA/AMPA ratio was 0.20${\pm}$0.05, AMPA receptor ratio of GluR2-lacking/GluR2-containing subunit was 0.26${\pm}$0.05 and NMDA receptor ratio of NR2B/NR2A subunit was 0.32${\pm}$0.03. The rectification index (control 2.39${\pm}$0.27) was decreased in the presence of both APV and combination of APV and IEM-1460 (1.02${\pm}$0.11 and 0.93${\pm}$0.09, respectively). These results suggest that the major components of the striatal glutamate receptors are GluR2-containing AMPA receptors and NR2A-containing NMDA receptors. Our results may provide useful information for corticostriatal synaptic transmission and plasticity studies.

• The Korean Journal of Physiology and Pharmacology
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• 제6권2호
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• pp.113-119
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• 2002

Long-term potentiation (LTP) at hippocampal CA3-CA1 synapses is often associated with increases in quantal size, traditionally attributed to enhanced availability or efficacy of postsynaptic glutamate receptors. However, augmented quantal size might also reflect increases in neurotransmitter concentration within the synaptic cleft since AMPA-type glutamate receptors are not generally saturated during basal transmission. Here we report evidence that peak cleft glutamate concentration $([glu]_{cleft})$ increases during LTP, as indicated by a lessening of the blocking effects of rapidly unbinding antagonists of AMPA. The efficacy of slowly equilibrating antagonists remained unchanged. The elevated $[glu]_{cleft}$ helps support the increased quantal amplitude of AMPA-type EPSCs (excitatory postsynaptic currents) during LTP.

• The Korean Journal of Physiology and Pharmacology
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• 제7권2호
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• pp.53-57
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• 2003

The glutamate receptors (GluRs) are key receptors for modulatory synaptic events in the central nervous system. It has been reported that glutamate increases the intracellular $Ca^{2+}$ concentration ($[Ca^{2+}]_i$) and induces cytotoxicity. In the present study, we investigated whether the glutamate-induced $[Ca^{2+}]_i$ increase was associated with the activation of ionotropic (iGluR) and metabotropic GluRs (mGluR) in substantia gelatinosa neurons, using spinal cord slice of juvenile rats (10${\sim}21 day). $[Ca^{2+}]_i$ was measured using conventional imaging techniques, which was combined with whole-cell patch clamp recording by incorporating fura-2 in the patch pipette. At physiological concentration of extracellular $Ca^{2+}$, the inward current and $[Ca^{2+}]_i$ increase were induced by membrane depolarization and application of glutamate. Dose-response relationship with glutamate was observed in both $Ca^{2+}$ signal and inward current. The glutamate-induced $[Ca^{2+}]_i$ increase at holding potential of -70 mV was blocked by CNQX, an AMPA receptor blocker, but not by AP-5, a NMDA receptor blocker. The glutamate-induced $[Ca^{2+}]_i$ increase in $Ca^{2+}$ free condition was not affected by iGluR blockers. A selective mGluR (group I) agonist, RS-3,5-dihydroxyphenylglycine (DHPG), induced $[Ca^{2+}]_i$ increase at holding potential of -70 mV in SG neurons. These findings suggest that the glutamate-induced $[Ca^{2+}]_i$ increase is associated with AMPA-sensitive iGluR and group I mGluR in SG neurons of rats.

• 생명과학회지
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• 제15권3호
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• pp.505-512
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• 2005

신경흥분독성과 간질발작발현은 glutamate 수용체활성과 연관이 있다고 알려져 있다. a-amino-3-hydroxy-5-methyl-4-isoxazole-propionate (AMPA), kainate 수용체에 대한 glutamate 활성을 포함하는 다양한 기전을 가진 항전간제인 Topiramate는 신경보호작용을 가진다는 증거가 제시되어 Topiramate가 간질발작 후 해마의 glutamate 수용체 발현에 미치는 효과를 관찰하였다. 흰쥐에 kainate를 복강 내 주사하여 간질중첩증을 유발시킨 후 Topiramate를 1주일 주사하였다 Apop tag in situ detection kit를 이용하여 세포손상을 관찰한 결과 kainate 유발 간질중첩증 1주일 후 해마의 CA1, CA3에서 심각한 세포사를 보였으나, Topiramte 처리 군에서는 세포사가 현저히 감소하였다. 간질중첩증 이후 NMDA 수용체 아형 1,2a, 2b 발현이 현저히 증가했으나 Topiramate 처치에 의해 NMDA수용체의 발현에는 뚜렷한 변화가 없었다. AMPA수용체에서는 GluR1이 간질중첩증 이후 현저히 상향 조정되었고 GluR2는 현저히 하향조정 되었다 Topiramate 1주일 처리 시 간질중첩증으로 인해 변화된 CluR1과 GluR2의 발현이 역전되었다. 결론적으로 Topiramate는 간질중침증에 의한 CluR1/CluR2 발현비의 증가로 유발되는 흥분성 신경세포사를 억제시킴으로써 신경보호작용이 있는 것으로 보인다.

• The Korean Journal of Physiology and Pharmacology
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• 제8권6호
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• pp.301-305
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• 2004

This study examined the effects of N-methyl-D-aspartate (NMDA), ${\alpha}-amino$-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) and kainate on basal and electrically-evoked release of acetylcholine (ACh) from the rat hippocampal and striatal slices which were preincubated with $[^3H]choline$. Unexpectedly, the basal and evoked ACh release were not affected at all by the treatment with NMDA $(3{\sim}100{\mu}M)$, AMPA $(1{\sim}100{\mu}M)$ or kainate $(1{\sim}100{\mu}M)$ in hippocampal slices. However, in striatal slices, under the $Mg^{2+}-free$ medium, $30{\mu}M$ NMDA increased the basal ACh release with significant decrease of the electrically-evoked releases. The treatment with $1{\mu}M MK-801 not only reversed the $30{\mu}M$ NMDA-induced decrease of the evoked ACh release, but also attenuated the facilitatory effect of $30\;{\mu}M$ NMDA on the basal ACh release. The treatment with either $30\;{\mu}M$ AMPA or $100\;{\mu}M$ kainate increased the basal ACh release without any effects on the evoked release. The treatment with $10{\mu}M$ NBQX abolished the AMPA- or kainate-induced increase of the basal ACh release. Interestingly, NBQX significantly attenuated the evoked release when it was treated with AMPA, although it did not affect the evoked release alone without AMPA. These observations demonstrate that in hippocampal slices, ionotropic glutamate receptors do not modulate the ACh release in cholinergic terminals, whereas in striatal slices, activations of ionotropic glutamate receptors increase the basal ACh release though NMDA may decrease the electrically-evoked ACh release.

• 생명과학회지
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• 제19권8호
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• pp.1055-1061
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• 2009

${\alpha}$-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) 수용체는 중추신경계에 널리 발현하며, 연접부위에서 글루타메이트에 의한 흥분성 신경전달의 역할을 행한다. 이러한 수용체의 조절은 학습과 기억에 관여한다. 본 연구에서는 AMPA receptor subunit glutamate receptor-interacting protein 1 (GRIP1)과 결합하는 단백질로 armadillo family인 p0071/plakophilin-4을 분리하였다. GRIPl 단백질은 p0071/plakophilin-4 단백질의 C-말단과 결합하며, armadillo family 단백질 중 p0071/plakophilin-4 과만 결합한다. 효모 two-hybrid assay에서 GRIPl의 Postsynaptic density-95/Discs large/Zona occludens-1 (PDZ) 영역이 p0071/plakophilin-4 단백질과의 결합에 관여하며, p0071/plakophilin-4 단백질의 C-말단 아미노산인 "S-X-V" 배열이 결합에 필수적이었다. 이러한 결합은 뇌 균질액에서 Glutathione S-transferase (GST) pull-down assay와 공면역침강법으로 확인하였다. 이러한 결과들은 AMPA 수용체가 연접후막에 안정적으로 위치하는 새로운 역할을 시사한다.

• The Korean Journal of Physiology and Pharmacology
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• 제7권6호
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• pp.375-379
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• 2003

$Ca^{2+}$ influx appears to be important for triggering myoblast fusion. It remains, however, unclear how $Ca^{2+}$ influx rises prior to myoblast fusion. Recently, several studies suggested that NMDA receptors may be involved in $Ca^{2+}$ mobilization of muscle, and that $Ca^{2+}$ influx is mediated by NMDA receptors in C2C12 myoblasts. Here, we report that other types of ionotropic glutamate receptors, non-NMDA receptors (AMPA and KA receptors), are also involved in $Ca^{2+}$ influx in myoblasts. To explore which subtypes of non-NMDA receptors are expressed in C2C12 myogenic cells, RT-PCR was performed, and the results revealed that KA receptor subunits were expressed in both myoblasts and myotubes. However, AMPA receptor was not detected in myoblasts but expressed in myotubes. Using a $Ca^{2+}$ imaging system, $Ca^{2+}$ influx mediated by these receptors was directly measured in a single myoblast cell. Intracellular $Ca^{2+}$ level was increased by KA, but not by AMPA. These results were consistent with RT-PCR data. In addition, KA-induced intracellular $Ca^{2+}$ increase was completely suppressed by treatment of nifedifine, a L-type $Ca^{2+}$ channel blocker. Furthermore, KA stimulated myoblast fusion in a dose-dependent manner. CNQX inhibited not only KA-induced myoblast fusion but also spontaneous myoblast fusion. Therefore, these results suggest that KA receptors are involved in intracellular $Ca^{2+}$ increase in myoblasts and then may play an important role in myoblast fusion.

• 대한약리학회지
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• 제31권2호
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• pp.141-144
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• 1995

뇌간의 세로트닌 신경계는 내재성 하행성 동통억제계(endogenous descending pain inhibitory system)에 있어서 중추적인 역할을 하고 있다. 뇌간의 세로토닌 신경세포에 대한 glutamate 수용체 중 N-methyl-D-aspartic acid-(NMDA-) 및 non-NMDA 수용체 효현제들의 작용을 알아보기 위하여, 쥐의 태자(태생 14일)로부터 뇌간을 분리하여 10일 동안 배양한 후 5-hydroxytryptamine(5-HT)의 분비에 대한 각 glutamate 수용체 효현제들이 영향을 연구하였다. Glutamate를 $10\;{\mu}M$에서 $1000\;{\mu}M$까지 농도를 변화하여 30분 동안 배지에 가한 후, 배지내에 분비되는 세로토닌을 측정한 결과, 농도 의존적으로 세로토닌의 분비가 증가되었다. Glutamate 수용체 중에서 NMDA 수용체 효현제인 NMDA를 $10\;{\mu}M$에서 $1000\;{\mu}M$까지 농도를 변화하여 30분 동안 배지에 가한 후, 배지내에 분비되는 세로토닌을 측정한 결과, 농도 의존적으로 세로토닌의 분비가 증가되었다. Non-NMDA 수용체 효현제인 kainate 및 AMPA를 $3\;{\mu}M$에서 $300\;{\mu}M$까지 농도를 변화하여 배지에 처리한 결과, 각 효현제에 의해 농도 의존적으로 세로토닌의 분비가 증가됨을 관찰하였다. 이상의 연구결과, 쥐의 태자(태생 14일)로부터 분리하여 10일동안 배양한 뇌간의 세로토닌 신경세포에 있어서 glutamate, NMDA, kainate 및 AMPA 모두 5-HT의 분비를 자극함으로써, NMDA- 및 non-NMDA 수용체 모두 5-HT의 분비에 관여하고 있음을 나타낸다.