• 한국식물학회:학술대회논문집
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• 한국식물학회 2001년도 춘계학술발표대회:발표눈문요지록
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• pp.11-11
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• 2001

• 약학회지
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• 제43권4호
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• pp.535-540
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• 1999

Glutamate (Glu) receptor-mediated excitoxicity has been implicated in many acute and chronic types of neurological disorders. Exposure of mature rat cortical neurons (15-18 days in culture) to the various concentrations of Glu resulted in a marked neuronal death, whereas immature rat cortical neurons (4∼5 days in culture) were resistant to the Glu-induced toxicity. Glu receptor subtype-specific agonists showed differential extent of toxicity in the immature neurons. The neurons treated with NMDA or kainate (KA) did not exhibit damage. However, quisqualate (QA) treatment induced a considerable cell death (36.1%) in immature enurons. The non-NMDA antagonist DNQX did not reduce this response. Interestingly, the QA-induced toxicity was potentiated by spermine in a concentration-dependent manner. Again, the spermine-enhanced damage was not altered by the polyamine antagonist ifenprodil. Taken together, unlike NMDA or KA, QA can induce neurotoxicity in immature rat cortical neurons and the QA-induced toxicity was potentiated by spermine. The lack of antagonizing effects of DNQX and ifenprodil on QA-induced toxicity and the potentiated toxicity by spermine, respectively, implies that both QA receptor and the polyamine site of NMDA receptor may not mediate the neurotoxicity observed in this study, and that a distinct mechanism(s) may be involved in excitotoxicity in immature neurons.

• International Journal of Oral Biology
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• 제42권2호
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• pp.55-61
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• 2017

Recent studies indicate that mitochondria are an important source of reactive oxygen species (ROS) in the spinal dorsal horn. In our previous study, application of malate, a mitochondrial electron transport complex I substrate, induced a membrane depolarization, which was inhibited by pretreatment with ROS scavengers. In the present study, we used patch clamp recording in the substantia geletinosa (SG) neurons of spinal slices, to investigate the cellular mechanism of mitochondrial ROS on neuronal excitability. DNQX (an AMPA receptor antagonist) and AP5 (an NMDA receptor antagonist) decreased the malate-induced depolarization. In an external calcium free solution and addition of tetrodotoxin (TTX) for blockade of synaptic transmission, the malate-induced depolarization remained unchanged. In the presence of DNQX, AP5 and AP3 (a group I metabotropic glutamate receptor (mGluR) antagonist), glutamate depolarized the membrane potential, which was suppressed by PBN. However, oligomycin (a mitochondrial ATP synthase inhibitor) or PPADS (a P2 receptor inhibitor) did not affect the substrates-induced depolarization. These results suggest that mitochondrial substrate-induced ROS in SG neuron directly acts on the postsynaptic neuron, therefore increasing the ion influx via glutamate receptors.

• 대한의생명과학회지
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• 제11권3호
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• pp.319-326
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• 2005

It is well known that oxidative stress of reactive oxygen species (ROS) may be a causative factor in the pathenogenesis of bone disorder on osteoblast or osteoclast. The purpose of this study was to evaluate the cytotoxicity of oxidative stress, protective effect of glutamate receptor antagoinst against ROS-induced osteotoxicity, secretion of tumor necrosis factor $(TNF)-\alpha$ and the expression of c-fos gene in the cultured rat osteoblasts and osteoclasts. Cell viability by MTS assay or !NT assay, activity of glutathione peroxidase (GPx), lipid peroxidation (LPO) activity, protein synthesis by sulforhodamine B (SRB) assay, alkaline phosphatase (ALP) activity, lactate dehydrogenase (LDH) activity, MTS assay for NMDA (N-methyl-D-aspartate) receptor antagonist or AMPA/kainate receptor antagonist, measurement for $TNF-\alpha$, and c-fos gene expression were performed after these cells were treated with or without various cocentrations of xanthine oxidase (XO), hypoxanthine (HX), D-2-amino-5-phosphonovaleric acid (APV), 7-chlorokynurenic acid (CKA), 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and 6,7-dinitroquinoxaline-2,3-dione (DNQX), respectively. In this study, XO/HX showed decreased cell viability and glutathione peroxidase (GPx) activity, but it showed increased LPO activity, $TNF-\alpha$ secretion and c-fos expression. APV and CKA incresed protein sythesis and ALP activity. While, CNQX or DNQX did not show any protective effect in LDH activity or cell viability. From these results, XO/HX showed cytotoxic effect in cultured rat osteoblast or osteoclast, and also NMDA receptor antagonist such as APV or CKA was effective in blocking XO/HX-induced osteotoxicity in these cultures.

• The Korean Journal of Physiology and Pharmacology
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• 제1권4호
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• pp.355-366
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• 1997

Although cerebellar Purkinje cells display spontaneous electrical activity in vivo and in slice experiments, the mechanism of the spontaneous activity generation has not been clearly understood. The aim of this study was to investigate whether cerebellar Purkinje cells of postnatal rats generate spontaneous electrical activity without synaptic inputs. Dissociated cerebellar Purkinje cells were used for reducing synaptic inputs in the present study. Cerebellar Purkinje cells with dendrites were dissociated from postnatal rats using enzymatic treatment followed by mechanical trituration. Spontaneous electrical activities were recorded from dissociated cells without any stimulus using whole-cell patch clamp configuration. Two types, spontaneously firing or quiescent, of dissociated Purkinje cells were observed in postnatal rats. Both types of cells were identified as Purkinje cells using immunocytochemical staining technique with anti-calbindin after recording. Spontaneously active cells displayed two patterns of firing, repetitive and burst firings. Two thirds of dissociated Purkinje cells displayed repetitive firing and the rest of them did burst firing under same recording condition. Repetitive firing activities were maintained even after further isolation using either physical or pharmacological techniques. Neither high magnessium solution nor excitatory synaptic blockers, AP-5 and DNQX, block the spontaneous activity. These results demonstrate that spontaneous electrical activity of isolated cerebellar Purkinje cells in postnatal rats is generated by intrinsic membrane properties rather than synaptic inputs.

• Archives of Pharmacal Research
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• 제22권1호
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• pp.35-43
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• 1999

Overstimulation of both kainate (KA) and N-methyl-D-aspartate (NMDA) receptors has been reported to induce excitatoxicity which can be characterized by neuronal damage and formation of reactive oxygen free radicals. Neuroprotective effect of melatonin against KA-induced excitotoxicity have been documented in vitro and in vivo. It is, however, not clear whether melationin is also neuroportective against excitotoxicity mediated by NMDA receptors. In the present work, we tested the in vivo protective effects of striatally infused melatonin against the oxidative stress and neuronal damage induced by the injection of KA and NMDA receptors into the rat striatum. Melatonin implants consisting of 22-gauge stainless-steel cannule with melatonin fused inside the tip were placed bilaterally in the rat brain one week prior to intrastriatal injection of glutamate receptor subtype agonists. Melatonin showed protective effects against the elevation of lipid peroxidation induced by either KA or NMDA and recovered Cu, Zn-superoxide dismutase activities reduced by both KA and NMDA into the control level. Melatonin also clearly blocked both KA- and NMDA-receptor mediated neuronal damage assessed by the determination of choline acetyltransferase activity in striatal monogenages and by microscopic observation of rat brain section stained with cresyl violet. The protective effects of melatonin are comparable to those of DNQX and MK801 which are the KA- and NMDA-receptor antagonist, respectively. It is suggested that melatonin could protect against striatal oxidative damages mediated by glutamate receptors, both non-NMDA and NMDA receptors.

• 동의생리병리학회지
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• 제17권4호
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• pp.996-1001
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• 2003

It is well known that oxidative stress of reactive oxygen species(ROS) may be a causative factor in the pathogenesis of bone disorder. The purpose of this study was to evaluate the cytotoxicity of oxidative stress. Cell viability by MTS assay or INT assay, activity of glutathione peroxidase(GPx), lipid peroxidation(LPO) activity and cell viablity. And also protctive effect of glutamate receptors against ROS-induced osteotoxicity was examined by protein synthesis, alkaline phosphatase (ALP) activity and lactate dehydrogenase (LDH) activity in cultured rat osteoblasts and osteoclasts. XO/HX decreased cell viability and GPx activity, protein synthesis and ALP activity, but increased LPO activity and LDH activity. In the protective effect, N-methyl-D-aspartate (NMDA) receptor antagonists or AMPA/kainate receptor antagonists such as D-2-amino-5-phosphonovaleric acid (APV), 7-chlorokynurenic acid (CKA), 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and 6,7-dinitroquinoxaline-2,3-dione (DNQX), NMDA receptor antagonists but AMPA/kainate receptor antagonists showed protective effect on xanthine oxidase (XO) and hypoxanthine (HX) in these cultures by the increse of protein synthesis, ALP activity.

• Archives of Pharmacal Research
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• 제18권3호
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• pp.153-158
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• 1995

The levels of extracellualr glutamate, intracellular $Ca^{2+}\;([Ca2+]_i)$ and cGMP were determined for 1 h with the excitatory amino acids, N-methyl-D-aspartate (NMDA) or kainate in cultured cerebellar granule cells. Both NMDA and kainate produced a time-dependent release of glutamate, and kainate was more potent than NMDA in glutamate elevation. The elevation of extracellular glutamate was not purely governed by intracellular $Ca^{2+}$ concentration. However, in opposite to the time-dependent elevation of glutamate, the elevation of cGMP by NMDA and kainate were at maximum level in short-time (1 min) incubation then remarkably decreased with longer incubation times. Post-applications (30 min after agonist) of EAA antagonist did not block EAAs-induced glutamate elevation. However, NMDA antagonist, phencyclidine (PCP), blocked NMDA-induced cGMP elevation at pre- or post-application, but kainate antagonist, 6,7-dinitroquinoxaline-2,3-dione (DNQX), paradoxically augmented kainate-induced cGMP elevation for 1 h incubation. These results show that NMDA or kainate induces time-dependent elevations of extracellular glutamate, while the elevations of cGMP by these EAAs are remarkably decreased with longer incubation times. However, NMDA- arid kainate-indcued glutamate release was blocked by pre-application of each receptor antagonist but not by post-application while EAA-induced $[Ca^{2+}]_i$ was blocked by post-application of antagonist. These observations suggest that EAA-induced elevation of $[Ca^{2+}]_i$ is not parallel with elevation of glutamate release or cGMP.