• The Korean Journal of Physiology and Pharmacology
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• v.1 no.6
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• pp.699-705
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• 1997

Although it is known that neuronal cell death during development occurs by apoptosis, the mechanisms underlying excitatory amino acid-induced neuronal cell death remain poorly understood. In this study we have examined the mechanism by which L-glutamate, an excitatory amino acid neurotransmitter, induces cell death in PC12 cell lines. To characterize cell death, we employed sandwich enzyme-linked immunosorbent assay(ELISA) method for cellular DNA fragmentation, DNA agarose gel electrophoresis and chromatin staining by acridine orange and ethidium bromide after treating the PC12 cells with L-glutamate. L-Glutamate caused dose-dependent cell death with a maximum at 24 hrs after the treatment. These cellular fragmentation was blocked by pretreatment of MK-801, a noncompetitive N-methyl-D-aspartic acid(NMDA) receptor antagonist, and nerve growth factor(NGF). Analysis of DNA integrity from L-glutamate-treated cells revealed cleavage of DNA into regular sized fragments, a biochemical hallmark of apoptosis. The PC12 cells that were induced to die by L-glutamate treatment exhibited classical chromatin condensation under the light microscopy after acridine orange and ethidium bromide staining. These results suggest that apoptosis is one of the key features that are involved in L-glutamate-induced excitotoxic cell death in PC12 cells, and these cell death are mediated by NMDA receptor and depend on NGF.

• The Korean Journal of Physiology and Pharmacology
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• v.21 no.1
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• pp.55-64
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• 2017

Progressive memory impairment such as that associated with depression, stroke, and Alzheimer's disease (AD) can interfere with daily life. In particular, AD, which is a progressive neurodegenerative disorder, prominently features a memory and learning impairment that is related to changes in acetylcholine and abnormal ${\beta}$-amyloid ($A{\beta}$) deposition in the brain. In the present study, we investigated the effects of dehydroevodiamine HCl (DHED) on cognitive improvement and the related mechanism in memory-impaired rat models, namely, a scopolamine-induced amnesia model and a $A{\beta}_{1-42}$-infused model. The cognitive effects of DHED were measured using a water maze test and a passive avoidance test in the memory-impaired rat models. The results demonstrate that DHED (10 mg/kg, p.o.) and Donepezil (1 mg/kg, p.o.) ameliorated the spatial memory impairment in the scopolamine-induced amnestic rats. Moreover, DHED significantly improved learning and memory in the $A{\beta}_{1-42}$-infused rat model. Furthermore, the mechanism of these behavioral effects of DHED was investigated using a cell viability assay, reactive oxygen species (ROS) measurement, and intracellular calcium measurement in primary cortical neurons. DHED reduced neurotoxicity and the production of $A{\beta}$-induced ROS in primary cortical neurons. In addition, similar to the effect of MK801, DHED decreased intracellular calcium levels in primary cortical neurons. Our results suggest that DHED has strong protective effects against cognitive impairments through its antioxidant activity and inhibition of neurotoxicity and intracellular calcium. Thus, DHED may be an important therapeutic agent for memory-impaired symptoms.

• The Korean Journal of Physiology and Pharmacology
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• v.8 no.6
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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.

• The Korean Journal of Physiology and Pharmacology
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• v.18 no.2
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• pp.135-141
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• 2014

The downregulation of A-type $K^+$ channels ($I_A$ channels) accompanying enhanced somatic excitability can mediate epileptogenic conditions in mammalian central nervous system. As $I_A$ channels are dominantly targeted by dendritic and postsynaptic processings during synaptic plasticity, it is presumable that they may act as cellular linkers between synaptic responses and somatic processings under various excitable conditions. In the present study, we electrophysiologically tested if the downregulation of somatic $I_A$ channels was sensitive to synaptic activities in young hippocampal neurons. In primarily cultured hippocampal neurons (DIV 6~9), the peak of $I_A$ recorded by a whole-cell patch was significantly reduced by high KCl or exogenous glutamate treatment to enhance synaptic activities. However, the pretreatment of MK801 to block synaptic NMDA receptors abolished the glutamate-induced reduction of the $I_A$ peak, indicating the necessity of synaptic activation for the reduction of somatic $I_A$. This was again confirmed by glycine treatment, showing a significant reduction of the somatic $I_A$ peak. Additionally, the gating property of $I_A$ channels was also sensitive to the activation of synaptic NMDA receptors, showing the hyperpolarizing shift in inactivation kinetics. These results suggest that synaptic LTP possibly potentiates somatic excitability via downregulating $I_A$ channels in expression and gating kinetics. The consequential changes of somatic excitability following the activity-dependent modulation of synaptic responses may be a series of processings for neuronal functions to determine outputs in memory mechanisms or pathogenic conditions.

• The Korean Journal of Pharmacology
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• v.32 no.2
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• pp.139-150
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• 1996

The effects of adenosine analogues on the electrically-evoked norepinephrine(NE) release and the influence of ischemia on the effects were studied in the rat hippocampus. Slices from the rat hippocampus were equilibrated with $0.1{\mu}M$ $[^3H]-norepinephrine$ and the release of the labelled product, $[^3H]-NE$, was evoked by electrical stimulation(3 Hz, 2 ms, 5 $VCm^{-1}$ and rectangular pulses for 90 sec), and the influence of various agents on the evoked tritium-outflow was investigated. Ischemia(15min with 95% $N_2$ +5% $CO_2$) increased both the basal and evoked NE release. These increases were abolished by addition of glucose into the superfused medium, and they were significantly inhibited either by $0.3\;{\mu}M$ tetrodotoxin pretreatment or by removing $Ca^{++}$ in the medium. MK-801$(1{sim}10\;{\mu}M)$, a specific NMDA receptor antagonist, and glibenclamide $(1\;{\mu}M)$, a $K^+-channel$ inhibitor, neither alter the evoked NE release nor affected the Ischemia-Induced increases in NE release. However, polymyxin B(0.03 mg), a specific protein kinase C inhibitor, inhibited the effect of ischemia on the evoked NE release. Adenosine and $N^6-cyclopentyladenosine$ decreased the NE release in a dose-dependent manner in ischemic condition, though the magnitude of inhibition was far less than those in normal (normoxic) condition. Also the treatment with $5{\mu}M$ DPCPX, a potent $A_1-adenosine$ receptor antagonist did not affect the ischemia-effect. These results suggest that the evoked-NE release is potentiated by ischemia, and this process being most probably mediated by protein kinase C, and that the decrease of NE release mediated through $A_1-adenosine$ receptor is significantly inhibited in ischemic state.

• The Korean Journal of Physiology and Pharmacology
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• v.19 no.3
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• pp.275-281
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• 2015

Orthostatic hypotension is most common in elderly people, and its prevalence increases with age. Attenuation of the vestibulo-sympathetic reflex (VSR) is commonly associated with orthostatic hypotension. In this study, we investigated the role of glutamate on the vestibulo-solitary projection of the VSR pathway to clarify the pathophysiology of orthostatic hypotension. Blood pressure and expression of both pERK and c-Fos protein were evaluated in the nucleus tractus solitarius (NTS) after microinjection of glutamate into the medial vestibular nucleus (MVN) in conscious rats with sodium nitroprusside (SNP)-induced hypotension that received baroreceptor unloading via sinoaortic denervation (SAD). SNP-induced hypotension increased the expression of both pERK and c-Fos protein in the NTS, which was abolished by pretreatment with glutamate receptor antagonists (MK801 or CNQX) in the MVN. Microinjection of glutamate receptor agonists (NMDA or AMPA) into the MVN increased the expression of both pERK and c-Fos protein in the NTS without causing changes in blood pressure. These results indicate that both NMDA and AMPA receptors play a significant role in the vestibulo-solitary projection of the VSR pathway for maintaining blood pressure, and that glutamatergic transmission in this projection might play a key role in the pathophysiology of orthostatic hypotension.

• The Korean Journal of Physiology and Pharmacology
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• v.21 no.6
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• pp.675-686
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• 2017

Orthostatic hypotension (OH) is associated with symptoms including headache, dizziness, and syncope. The incidence of OH increases with age. Attenuation of the vestibulosympathetic reflex (VSR) is also associated with an increased incidence of OH. In order to understand the pathophysiology of OH, we investigated the physiological characteristics of the VSR in the disorder. We applied sodium nitroprusside (SNP) to conscious rats with sinoaortic denervation in order to induce hypotension. Expression of pERK in the intermediolateral cell column (IMC) of the T4~7 thoracic spinal regions, blood epinephrine levels, and blood pressure were evaluated following the administration of glutamate and/or SNP. SNP-induced hypotension led to increased pERK expression in the medial vestibular nucleus (MVN), rostral ventrolateral medullary nucleus (RVLM) and the IMC, as well as increased blood epinephrine levels. We co-administered either a glutamate receptor agonist or a glutamate receptor antagonist to the MVN or the RVLM. The administration of the glutamate receptor agonists, AMPA or NMDA, to the MVN or RVLM led to elevated blood pressure, increased pERK expression in the IMC, and increased blood epinephrine levels. Administration of the glutamate receptor antagonists, CNQX or MK801, to the MVN or RVLM attenuated the increased pERK expression and blood epinephrine levels caused by SNP-induced hypotension. These results suggest that two components of the pathway which maintains blood pressure are involved in the VSR induced by SNP. These are the neurogenic control of blood pressure via the RVLM and the humoral control of blood pressure via epinephrine release from the adrenal medulla.

• Archives of Pharmacal Research
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• v.29 no.8
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• pp.677-684
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• 2006

Morphine has been used widely on the treatment of many types of chronic pain. However the development of tolerance to and dependence on morphine by repeat application is a major problem in pain therapy. The purpose of the present study was to investigate whether combined administration of nalbuphine with morphine affects the development of tolerance to and dependence on morphine. We hypothesize that the use of nalbuphine, ${\kappa}-agonist$ may prove to be useful adjunct therapy to prevent morphine-induced undesirable effects in the management of some forms of chronic pain. Morphine (10 mg/kg) was injected to rats intraperitoneally for 5 day. The variable dose of nalbuphine (0.1, 1.0 and 5.0 mg/kg) was administered (i.p.) in combination with morphine injection. The development of morphine tolerance was assessed by measuring the antinociceptive effect with the Randall-Selitto apparatus. The development of dependence on morphine was determined by the scoring the precipitated withdrawal signs for 30 min after injection of naloxone (10 mg/kg, i.p.). Nalbuphine did not attenuate antinociceptive effect of morphine in rats. Interestingly, combined administration of morphine with nalbuphine (10:1) significantly attenuated the development of dependence on morphine. The elevation of $[^3H]MK-801$ binding in frontal cortex, dentate gyrus, and cerebellum after chronic morphine infusion was suppressed by the coadministration of nalbuphine. In addition, the elevation of NR1 expression by morphine was decreased by the coadministration of nalbuphine in rat cortex. These results suggest that the coadministration of nalbuphine with morphine in chronic pain treatment can be one of therapies to reduce the development of tolerance to and dependence on morphine.

• Biomolecules & Therapeutics
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• v.25 no.3
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• pp.249-258
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• 2017

To examine the effect of biflorin, a component of Syzygium aromaticum, on memory deficit, we introduced a scopolamine-induced cognitive deficit mouse model. A single administration of biflorin increased latency time in the passive avoidance task, ameliorated alternation behavior in the Y-maze, and increased exploration time in the Morris water maze task, indicating the improvement of cognitive behaviors against cholinergic dysfunction. The biflorin-induced reverse of latency in the scopolamine-treated group was attenuated by MK-801, an NMDA receptor antagonist. Biflorin also enhanced cognitive function in a naïve mouse model. To understand the mechanism of biflorin for memory amelioration, we performed Western blot. Biflorin increased the activation of protein kinase C-${\zeta}$ and its downstream signaling molecules in the hippocampus. These results suggest that biflorin ameliorates drug-induced memory impairment by modulation of protein kinase C-${\zeta}$ signaling in mice, implying that biflorin could function as a possible therapeutic agent for the treatment of cognitive problems.

• Journal of Physiology & Pathology in Korean Medicine
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• v.37 no.2
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• pp.36-44
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• 2023

Essential oils and aromatherapy have traditionally been used for the treatment of anxiety and depression with few side effects. This study aimed to investigate the effects of essential oils from six herbal prescriptions known to be effective in treating anxiety and depression in Korean medicine. The neuroprotective and anti-neuroinflammatory effects of six essential oils, including Gamisachil-tang (GMSCT), Guibi-tang (GBT), Sihogayonggolmoryeo-tang (SYM), Danchisoyosan (DCSYS), Sihosogansan (SHSGS), and Soyosan (SYS), were examined in PC12 and BV2 cells. In corticosterone (CORT)-stimulated PC12 cells, all six essential oils ameliorated the CORT-induced decrease in cell viability at a concentration of 10 ㎍/ml. GMSCT, GBT, and SHSGS recovered CORT-induced cytotoxicity at concentrations of 1 ㎍/ml and 10 ㎍/ml. In lipopolysaccharide (LPS)-stimulated BV2 cells, GBT (10 ㎍/ml) decreased interleukin (IL)-1β production, whereas SHSGS (1 ㎍/ml) inhibited tumor necrosis factor (TNF)-α production. In the MK-801-induced anxiety in zebrafish, electroencephalogram (EEG) assessment indicated that GMSCT and SHSGS induced recovery in the delta and beta power densities and reduced theta/beta and delta/beta ratios. DCSYS and SYS decreased theta power density and theta/beta ratio, whereas GBT and SYM showed no effects on EEG signals. In the tail suspension test (TST) in mice, GBT, DCSYS, SHSGS, and SYS exhibited antidepressant-like effects by decreasing immobility time. These results suggest that the essential oils from the six herbal prescriptions, except SYM, may have beneficial effects on anxiety and/or depression. Further studies should be conducted to investigate the molecular signaling pathways that mediate the effects of these essential oils on anxiety and depression.