• The Korean Journal of Physiology and Pharmacology
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• 제15권2호
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• pp.95-100
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• 2011

DREAM (downstream regulatory element antagonistic modulator) is a calcium-binding protein that regulates dynorphin expression, promotes potassium channel surface expression, and enhances presenilin processing in an expression level-dependent manner. However, no molecular mechanism has yet explained how protein levels of DREAM are regulated. Here we identified group I mGluR (mGluR1/5) as a positive regulator of DREAM protein expression. Overexpression of mGluR1/5 increased the cellular level of DREAM. Up-regulation of DREAM resulted in increased DREAM protein in both the nucleus and cytoplasm, where the protein acts as a transcriptional repressor and a modulator of its interacting proteins, respectively. DHPG (3,5-dihydroxyphenylglycine), a group I mGluR agonist, also up-regulated DREAM expression in cortical neurons. These results suggest that group I mGluR is the first identified receptor that may regulate DREAM activity in neurons.

• International Journal of Oral Biology
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• 제36권2호
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• pp.71-78
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• 2011

Using whole cell current- and voltage-clamp recording we investigated the characteristics and pharmacology of group I metabotropic glutamate receptor (mGluR)-mediated responses in rat medial vestibular nucleus (MVN) neurons. In current clamp conditions, activation of mGluR I by application of the group I mGluR agonist (R,S)-3,5-dihydroxyphenylglycine (DHPG) induced a direct excitation of MVN neurons that is characterized by depolarization and increased spontaneous firing frequency. To identify which of mGluR subtypes are responsible for the various actions of DHPG in MVN, we used two subtype-selective antagonists. (S)-(+)- alpha-amino-a-methylbenzeneacetic acid (LY367385) is a potent competitive antagonist that is selective for mGluR1, whereas 2-methyl-6-(phenylethynyl)-pyridine (MPEP) is a potent noncompetitive antagonist that is selective for mGluR5. In voltage clamp conditions, DHPG application increased the frequency of spontaneous and miniature inhibitory postsynaptic currents (IPSCs) but had no effect on amplitude distributions. Antagonism of the DHPG-induced increase of miniature IPSCs required the blockade of both mGluR1 and mGluR5. DHPG application induced an inward current, which can be enhanced under depolarized conditions. DHPG-induced current was blocked by LY367385, but not by MPEP. Both LY367385 and MPEP antagonized the DHPG-induced suppression of the calcium activated potassium current ($I_{AHP}$). These data suggest that mGluR1 and mGluR5 have similar roles in the regulation of the excitability of MVN neurons, and show a little distinct. Furthermore, mGluR I, via pre- and postsynaptic actions, have the potential to modulate the functions of the MVN.

• 동의생리병리학회지
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• 제25권5호
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• pp.881-886
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• 2011

AMPA receptor (AMPAR)s are heterotetrameric structures made up from 4 units (GluR1-4) and are thought to underlie perception of persistent inflammatory pain. Complete Freund's adjuvant (CFA)-evoked inflammation induces synaptic GluR2 internalization, which is initiated by GluR2 phosphorylation, in dorsal horn neurons during the maintenance of CFA-induced hypersensitivity. The present study investigated whether electroacupuncture (EA) stimulation has any effect on GluR2 trafficking by using immunoblot and immunohistochemistry. We examined that CFA-induced dorsal horn GluR2 internalization was attenuated by EA treatment. EA treatment could also decrease the level of pGluR2 regardless of whether CFA injection was administrated or not. In addition, previous studies suggest that microglial cells are increased without morphological change in CFA injected animal. In our study, increases in microglial cells in CFA group were observed, whereas EA with or without CFA-injected group showed similar aspects with normal group. In conclusion, our results indicate that EA might blunt CFA-evoked inflammation by coordinating mechanisms at the upstream step of neuron activation and GluR2 phosphorylation.

• 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.

• 생명과학회지
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• 제20권1호
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• pp.1-8
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• 2010

본 연구자들의 앞선 연구에서는 햄스터 상구에서 AMPA 수용체의 아형인 GluR1과 GluR4의 분포와 눈 적출 이후 이들 수용체의 분포를 면역세포화학적 방법으로 연구하였다. 또한, 표지한 GluR1과 GluR4를 칼슘결합단백질인 calbindin D28K, calretinin, parvalbumin과 GABA로 표지하여 비교하였다. 본 연구에서 역행성이동추적물질(retrograde tracer)인 호스래디시퍼옥시다아제(horseradish peroxidase, HRP)를 상구의 각 주요 상행로와 하행로에 주입함으로써 GluR1- 면역반응 신경세포들과 GluR4- 면역반응 신경세포들이 투사신경세포(projection neurons)임을 밝혀내었다. Tecto-reticulospinal pathway (TRS)와 dorsal lateral geniculate nucleus (dLGN)으로 HRP 를 주입한후, 햄스터들은 회복을 위해 48시간 동안 살려둔 뒤 관류(perfusion)하였다. GluR- 면역반응 처리된 절편들은 역행성 표지된 신경세포를 지님을 확인하였다. HRP를 주입하였더니 단지 적은 수의 GluR1- 면역반응 신경세포들이 TRS (1.4%)와 dLGN (2.6%)으로 투사되었고, 반면에 많은 수의 GluR4- 면역반응 신경세포들이 TRS (32.7%)로 투사되었다. 사이/투사 신경세포(inter/projection neurons)들은 GluR 아단위들의 분류된 분포와 차별화된 양상을 보였고 이들의 이러한 분포는 칼슘결합단백질들과 GABA와는 겹쳐지지 않았으며, 일전에 발표했던 시각적 행동 반응에서 안구 적출 후 수용체 아단위들의 기능적 다양화와는 차별화된 양상을 보였다.

• 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.

• The Korean Journal of Physiology and Pharmacology
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• 제16권2호
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• pp.139-144
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• 2012

It has been reported that activation of metabotropic glutamate receptor 1 (mGluR1) can mediate endocannabinoid-induced short-term depression of synaptic transmission in cerebellar parallel fiber (PF)-Purkinje cell (PC) synapse. mGluR1 has signaling pathways involved in intracellular calcium increase which may contribute to endocannabinoid release. Two major mGluR1-evoked calcium signaling pathways are known: (1) slow-kinetic inward current carried by transient receptor potential canonical (TRPC) channel which is permeable to $Ca^{2+}$; (2) $IP_3$-induced calcium release from intracellular calcium store. However, it is unclear how much each calcium source contributes to endocannabinoid signaling. Here, we investigated whether calcium influx through mGluR1-evoked TRPC channel contributes to endocannabinoid signaling in cerebellar Purkinje cells. At first, we applied SKF96365 to inhibit TRPC, which blocked endocannabinoid-induced short-term depression completely. However, an alternative TRP channel inhibitor, BTP2 did not affect endocannabinoid-induced short-term depression although it blocked mGluR1-evoked TRPC currents. Endocannabinoid signaling occurred normally even though the TRPC current was mostly blocked by BTP2. Our data imply that TRPC current does not play an important role in endocannabinoid signaling. We also suggest precaution in applying SKF96365 to inhibit TRP channels and propose BTP2 as an alternative TRPC inhibitor.

• The Korean Journal of Physiology and Pharmacology
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• 제13권6호
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• pp.455-460
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• 2009

Glutamate-induced cobalt uptake reveals that non-NMDA glutamate receptors (GluRs) are present in rat taste bud cells. Previous studies involving glutamate induced cobalt staining suggest this uptake mainly occurs via kainate type GluRs. It is not known which of the 4 types of taste bud cells express subunits of kainate GluR. Circumvallate and foliate papillae of Sprague-Dawley rats (45~60 days old) were used to search for the mRNAs of subunits of non-NMDA GluRs using RT-PCR with specific primers for GluR1-7, KA1 and KA2. We also performed RT-PCR for GluR5, KA1, $PLC\beta2$, and NCAM/SNAP 25 in isolated single cells from taste buds. Taste epithelium, including circumvallate or foliate papilla, express mRNAs of GluR5 and KA1. However, non-taste tongue epithelium expresses no subunits of non-NMDA GluRs. Isolated single cell RT-PCR reveals that the mRNAs of GluR5 and KA1 are preferentially expressed in Type II and Type III cells over Type I cells.

• The Korean Journal of Pain
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• 제18권1호
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• pp.1-9
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• 2005

Background: Spinal metabotropic glutamate receptors (mGluRs) and opioid receptors are involved in the modulation of nociception. Although opioid receptors agonists are active for pain, the effects of the compounds for the mGluRs have not been definitely investigated at the spinal level. We examined the effects of the intrathecal mGluR compounds and morphine in the nociceptive test, and then we further clarified the role of the spinal mGluRs. In addition, the nature of the pharmacological interaction after the coadministration of mGluRs compounds with morphine was determined. Methods: Catheters were inserted into the intrathecal space of male SD rats. For the induction of pain, $50{\mu}l$ of 5% formalin solution or a thermal stimulus was applied to the hindpaw. An isobolographic analysis was used for the evaluation of the drug interaction. Results: Neither group I mGluR compounds nor group III mGluR compounds produced any antinociceptive effect in the formalin test. The group II mGluR agonist (APDC) had little effect on the formalin-induced nociception. The group II mGluR antagonist (LY 341495) caused a dose-dependent suppression of the phase 2 flinching response on the formalin test, but it did not reduce the phase 1 response of the formalin test nor did it increase the withdrawal latency of the thermal stimulus. Isobolographic analysis revealed a synergistic interaction after the intrathecal delivery of a LY 341495-morphine mixture. Conclusions: These results suggest that group II mGluRs are involved in the facilitated processing at the spinal level, and the combination of LY 341495 with morphine may be useful to manage the facilitated pain state.

• Molecules and Cells
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• 제21권3호
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• pp.418-427
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• 2006

Ionotropic glutamate receptors (iGluRs) are ligand-gated nonselective cation channels that mediate fast excitatory neurotransmission. Although homologues of the iGluRs have been identified in higher plants, their roles are largely unknown. In this work we isolated a full-length cDNA clone (RsGluR) encoding a putative glutamate receptor from small radish. An RsGluR:mGFP fusion protein was localized to the plasma membrane. In Arabidopsis thaliana overexpressing the fulllength cDNA, glutamate treatment triggered greater $Ca^{2+}$ influx in the root cells of transgenic seedlings than in those of the wild type. Transgenic plants exhibited multiple morphological changes such as necrosis at their tips and the margins of developing leaves, dwarf stature with multiple secondary inflorescences, and retarded growth, as previously observed in transgenic Arabidopsis overexpressing AtGluR3.2 [Kim et al. (2001)]. Microarray analysis showed that jasmonic acid (JA)-responsive genes including defensins and JA-biosynthetic genes were up-regulated. RsGluR overexpression also inhibited growth of a necrotic fungal pathogen Botrytis cinerea possibly due to up-regulation of the defensins. Based on these results, we suggest that RsGluR is a glutamate-gated $Ca^{2+}$ channel located in the plasma membrane of higher plants and plays a direct or indirect role in defense against pathogen infection by triggering JA biosynthesis.