• The Korean Journal of Physiology and Pharmacology
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• v.19 no.2
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• pp.177-181
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• 2015

The subfornical organ (SFO) is one of circumventricular organs characterized by the lack of a normal blood brain barrier. The SFO neurons are exposed to circulating glutamate ($60{\sim}100{\mu}M$), which may cause excitotoxicity in the central nervous system. However, it remains unclear how SFO neurons are protected from excitotoxicity caused by circulating glutamate. In this study, we compared the glutamate-induced whole cell currents in SFO neurons to those in hippocampal CA1 neurons using the patch clamp technique in brain slice. Glutamate ($100{\mu}M$) induced an inward current in both SFO and hippocampal CA1 neurons. The density of glutamate-induced current in SFO neurons was significantly smaller than that in hippocampal CA1 neurons (0.55 vs. 2.07 pA/pF, p<0.05). To further identify the subtype of the glutamate receptors involved, the whole cell currents induced by selective agonists were then compared. The current densities induced by AMPA (0.45 pA/pF) and kainate (0.83 pA/pF), non-NMDA glutamate receptor agonists in SFO neurons were also smaller than those in hippocampal CA1 neurons (2.44 pA/pF for AMPA, p<0.05; 2.34 pA/pF for kainate, p< 0.05). However, the current density by NMDA in SFO neurons was not significantly different from that of hippocampal CA1 neurons (1.58 vs. 1.47 pA/pF, p>0.05). These results demonstrate that glutamate-mediated action through non-NMDA glutamate receptors in SFO neurons is smaller than that of hippocampal CA1 neurons, suggesting a possible protection mechanism from excitotoxicity by circulating glutamate in SFO neurons.

• Toxicological Research
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• v.22 no.3
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• pp.275-282
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• 2006

In previous our studies, we have reported that eugenol derived from Eugenia caryophyllata(Myrtaceace) exhibits acute N-methyl-D-aspartate(NMDA)- and oxygen/glucose deprivation-induced neurotoxicity in primary cortical cultures and protects hippocampal neurons from global ischemia. In this study, we investigated whether the extracts and fractions of E. caryophyllata or eugenol shows the neuroprotective effects against delayed neuronal injury evoked by NMDA or ${\alpha}$-amino-3-hydroxy-5-methylisoxazole propionate(AMPA), and oxidative damage induced by arachidonic acid-, hydrogen peroxide-, $FeCl_2$/ascorbic acid-, and buthionine sulfoximine(BSO) in primary cortical cultures. We examined the neurotoxicity of eugenol itself in cultures and inhibitory effect of eugenol on NMDA- or kainate(KA)-induced convulsion in BALB/c mice. Each water, methanol extract and methanol fraction of E. caryophyllata was significantly attenuated NMDA-induced delayed neurotoxicity, respectively. Eugenol exhibited a significant inhibitory action against the convulsion evoked by NMDA and KA, and reduced delayed or brief neurotoxicity induced by NMDA, AMPA, and various oxidative injuries. These results suggest that eugenol derived from E. caryophyllata may contribute the neuroprotection against delayed-type excitotoxicity and excitotoxins-mediated convulsion through the amelioration of oxidative stress.

• Journal of Physiology & Pathology in Korean Medicine
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• v.20 no.6
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• pp.1672-1677
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• 2006

Sarcodon aspratus is the mushroom of Telephoracea which was been classified into Alphllophorales. The aqueous extract of Sarcodon aspratus in known to have anti-tumor activity, immune modulatory effect, and anti-oxidative action. The descending pain control system consists of three major components: the periaqueductal gray (PAG) of the midbrain, the rostroventral medulla including the nucleus raphe magnus, and the spinal dorsal horn. Glutamate is the primary excitatory neurotransmitter in the brain. Glutamate ionotropic receptors are classified as N-methyl-D-aspartate (NMDA) receptor, ${\alpha}$-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptor, and kainate receptor. In the present study, the modulation of Sarcodon aspratus on the ion currents activated by glutamate, NMDA, AMPA, and kainate in the acutely dissociated PAG neurons was investigated by nystatin-perforated patch-clamp technique under boltage-clamp condition. Sarcodon aspratus increased glutamate- and NMDA-induced ion currents were not increased by Sarcodon aspratus. The present results show that Sarcodon aspratus may activate the descending pain control system in rat PAG neurons through NMDA receptor.

• The Korean Journal of Physiology and Pharmacology
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• v.7 no.6
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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.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2009.11a
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• pp.190-192
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• 2009

Kainic acid (KA), an agonist for kainate and AMPA receptors, is an excitatory neurotoxic substance. Vitamin E such as alpha-tocopherol and alpha-tocotrienol is a chain-breaking antioxidant, preventing the chain propagation step during lipid peroxidation. In the present study, we have investigated the neuroprotective effects of alphatocopherol and alpha-tocotrienol on KA-induced neuronal death using organotypic hippocampal slice culture (OHSC). After 15h KA treatment, delayed neuronal death was detected in CA3 region. Alpha-tocopherol and alpha-tocotrienol increased cell survival and reduced the number of TUNEL-positive cells in CA3 region. These data suggest that alpha-tocopherol and alpha-tocotrienol treatment have protective effects on KA-induced cell death

• Proceedings of the Korean Biophysical Society Conference
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• 2003.06a
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• pp.40-40
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• 2003

Spontaneous firing rate and patterns of dopaminergic neurons in midbrain are key factors in determining the level of dopamine at target loci as well as in the mechanisms such as reward and motor coordination. Although glutamate, as a major afferent, is reported to enhance firing rate, the detailed actions of NMDA-, AMPA/kainate-, and metabotropic glutamate receptors (mGluR) on filing patterns are not clear. Thus we have investigated the role of glutamate receptors on the spontaneous firing activities using the network-free, acutely isolated dopamine neurons from substantia nigra pars compacta(SNc) of the 9-14 days rat. The isolated cells showed spontaneous regular firings of near 2.5 Hz, whose rate was enhanced by glutamate at submicromolar levels (0.3 $\square$M) but abolished by high concentrations more than 10 $\square$M.

• Journal of Physiology & Pathology in Korean Medicine
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• v.18 no.2
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• pp.586-595
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• 2004

Kamidojuk-San (KDJS) is known to be effective for treating cardiovascular diseases such hypertension, and clinically applied for the treatment of cerebral palsy or stoke patients. Yet, the overall mechanisms underlying its activity at the cellular levels are not known. Using experimental animal system, we investigated whether KDJS has protective effects on cells in cardiovascular and nervous systems. KDJS was found to rescue death of cultured primary neurons induced by AMPA, NMDA and kainate as well as BSO and Fe/sup 2+/ treatments. Moreover, KDJS treatment promoted animal's recovery from coma induced by a lethal dose of KCN treatment, and improved survival in animals exposed to lethal dose of KCN. Neurological examinations further showed that KDJS reduced the time which is required for animals to respond in terms of forelimb and hindlimb movements. To examine its physiological effects on cardiovascular and nervous systems, we induced ischemic injury in hippocampal neurons and cerebral neurons by middle cerebral artery (MCA) occlusion. Histological examination revealed that KDJS significantly protected neurons from ischemic damage. Thus, the present data suggest that KDJS may play an important role in protecting cells of cardiovascular and nervous systems from external noxious stimulations.

• Biomedical Science Letters
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• v.11 no.3
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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.

• Journal of Physiology & Pathology in Korean Medicine
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• v.18 no.1
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• pp.265-273
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• 2004

KBPTS is the fortified prescription of Bang-pung-tong-sung-san (BPTS) by adding Spatholobi Clulis and Salviae Miltiorrzae Radix. BPTS prescription has been used in Qriental medicine for the treatments of vascular diseases including hypertension, stroke, and arteriosclerosis, and nervous system diseases. Yet, the overall mechanism underlying its activity at the cellular levels remains unknown. To investigate the protective role of KBPTS on brain functions, noxious stimulations were applied to neurons in vitro and in vivo. KBPTS pretreatment in cultured cortical neurons of albino ICR mice rescued death caused by AMPA, NMDA, and kainate as well as by buthionine sulfoximine (BSO) and ferrous chloride (Fe/sup 2+/) treatments. Furthermore, KBPTS promoted animal's recovery from coma induced by a sublethal dose of KCN and improved survival by a lethal dose of KCN. To examine its physiological effects on the nervous system, we induced ischemia in the Sprague-Dawley rat's brain by middle cerebral artery (MCA) occlusion. Neurological examination showed that KBPTS reduced the time which is required for the animal after MCA occlusion to respond in terms of forelimb and hindlimb movement$. Histological examination revealed that KBPTS reduced ischemic area and edema rate and also protected neurons in the cerebral cortex and hippocampus from ischemic damage. Thus, the present data suggest that KBPTS may play an important role in protecting neuronal cells from external noxious stimulations.

• The Journal of Korean Medicine
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• v.24 no.3
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• pp.72-83
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• 2003

Objective : The goal of the present study was to investigate the protective effect of Gamiheechum-tang (Jiaweixiqian-tang; GHCT) on brain tissue damage from chemical or ischemic insults. Methods : Levels of cultured cortical neuron death caused by toxic chemicals were measured by LDH release assay. Neuroprotective effects of GHCT on brain tissues were examined in vivo by ischemic model of middle cerebral artery (MCA) occlusion. Results : Animal groups treated with GBCT showed significantly decreased hypertension, and reduced levels of aldosterone, dopamine, and epinephrine in the plasma. GHCT treatments ($l0-200\mu\textrm{g}/ml$) significantly decreased cultured cortical neuron death mediated by AMPA, kainate, BSO, or Fe2+ when measured by LDH release assay. Yet, cell death mediated by NMDA was effectively protected by GHCT at the highest concentration examined ($200\mu\textrm{g}/ml$). In the in vivo experiment examining brain damage by MCA occlusion, affected brain areas by ischemic damage and edema were significantly less in animal groups administered with GHCT compared to the non-treated control group. Neurological examinations of forelimbs and hindlimbs showed that GHCT treatment improved animals' recovery from ischemic injury. Moreover, the extent of injury in cortical and hippocampal pyramidal neurons in ischemic rats was much reduced by GHCT, whose morphological features were similarly observed in non-ischemic animals. Conclusion : The present data suggest that GBCT may play an important role in protecting brain tissues from chemical or ischemic injuries.