• The Korean Journal of Physiology and Pharmacology
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• v.28 no.2
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• pp.165-181
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• 2024

The slow and regular pacemaking activity of midbrain dopamine (DA) neurons requires proper spatial organization of the excitable elements between the soma and dendritic compartments, but the somatodendritic organization is not clear. Here, we show that the dynamic interaction between the soma and multiple proximal dendritic compartments (PDCs) generates the slow pacemaking activity in DA neurons. In multipolar DA neurons, spontaneous action potentials (sAPs) consistently originate from the axon-bearing dendrite. However, when the axon initial segment was disabled, sAPs emerge randomly from various primary PDCs, indicating that multiple PDCs drive pacemaking. Ca²⁺ measurements and local stimulation/perturbation experiments suggest that the soma serves as a stably-oscillating inertial compartment, while multiple PDCs exhibit stochastic fluctuations and high excitability. Despite the stochastic and excitable nature of PDCs, their activities are balanced by the large centrally-connected inertial soma, resulting in the slow synchronized pacemaking rhythm. Furthermore, our electrophysiological experiments indicate that the soma and PDCs, with distinct characteristics, play different roles in glutamate-induced burst-pause firing patterns. Excitable PDCs mediate excitatory burst responses to glutamate, while the large inertial soma determines inhibitory pause responses to glutamate. Therefore, we could conclude that this somatodendritic organization serves as a common foundation for both pacemaker activity and evoked firing patterns in midbrain DA neurons.

• Animal cells and systems
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• v.15 no.4
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• pp.279-286
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• 2011

Hypoxic ischemia injury is a common cause of functional brain damage, resulting from a decrease in cerebral blood flow and oxygen supply to the brain. The main problems associated with hypoxic ischemia to the brain are memory impairment and dopamine dysfunction. Hypothermia has been suggested to ameliorate the neurological impairment induced by various brain insults. In this study, we investigated the effects of hypothermia on memory function and dopamine synthesis following hypoxic ischemia to the brain in rats. For this purpose, a step-down avoidance task, a radial eight-arm maze task, and immunohistochemistry for tyrosine hydroxylase (TH) and 5-bromo-2'-deoxyuridine (BrdU) were performed. The present results indicated that the hypoxic ischemia-induced disturbance of the animal's performances and spatial working memory was associated with a decrement in TH expression in the substantia nigra and striatum, and an increase in cell proliferation in the hippocampal dentate gyrus. Hypothermia treatment improved the animals' performance and spatial working memory by suppressing the decrement in TH expression in the substantia nigra and striatum and the increase in cell proliferation in the dentate gyrus. We suggest that hypothermia can be an efficient therapeutic modality to facilitate recovery following hypoxic ischemia injury to the brain, presumably by modulating the dopaminergic cell loss.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.16 no.2
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• pp.160-172
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• 2005

Attention-Deficit/Hyperactivity Disorder(ADHD) is the most common neurodevelopmental disorder in child psychiatry. The etiology or ADHD is not completely understood, but involved in genetical and/or neurocognitive deficits. This article reviews the current state of the literature pertaining to the neurodevelopmental aspects of ADHD. Although the neurodevelopment of ADHD remains unclear, emerging evidence documents its genetic and neurobiologic underpinnings. A pathophysiology of ADHD has not been fully characterized, although genetic, neurobiologic, neuroimaging, and neuropsychological studies of ADHD consistently implicates dysfunction in the fronto-subcortical network and abnormality in the dopaminergic and noradnergic systems. Furthermore some suggests that the timing of aberrant brain development in ADHD could be in early gestation and genetic and/or early environmental influences on brain development in ADHD are fixed, nonprogressive. Although many studies provide evidences for the important or psychosocial or environmental adversities in ADHD, they may be not specific predictors of ADHD but nonspecific triggers of an underlying predisposition or modifiers of the course of disorder.

• Journal of Oriental Neuropsychiatry
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• v.28 no.3
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• pp.145-156
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• 2017

Objectives: The purpose of this study is to review experimental studies of Parkinson's Disease in Korean medical journals, which have been published since 1990. Methods: Experimental studies related to Parkinson's disease published in Korean medical journals, registered with Korea research foundation, were searched. Articles were grouped into journal of publication, subject, and publication year. Experimental study subjects and models were analysed. Results and Conclusions: Twenty-two articles about experimental studies of Parkinson's Disease in Korean medical journals were included in our review. There were 13 articles in which herbs were used for treatment, 4 articles in which bee venom was used for treatment, 4 articles in which acupuncture was used for treatment, and 1 article in which pharmacopuncture was used for treatment. Most of the studies used experimental models of MPTP-induced Parkinson's disease and MTT assay was used to analyse cell toxicity and cell viability. Pole test, rotarod test, Morris water maze test, and forced swimming test were commonly used to analyse MPTP-induced behavioral deficits in animals. Analysis on experimental studies of Parkinson's disease was categorized into the subjects of dopaminergic cell protective effect, cell-apoptosis protectiveness, anti-inflammatory effect, and anti-oxidative effect.

• The Korean Journal of Physiology and Pharmacology
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• v.19 no.2
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• pp.89-97
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• 2015

The aim of this study was to investigate the involvement of dopaminergic receptors (DR) in behavioral sensitization, as measured by locomotor activity, and the over-expression of cocaine- and amphetamine-regulated transcript (CART) peptides after repeated administration of cocaine in mice. Repeated administrations of cocaine induced behavioral sensitization and CART over-expression in mice. The levels of striatal CART mRNA were significantly increased on the $3^{rd}$ day. CART peptides were over-expressed on the $5^{th}$ day in the striata of behaviorally sensitized mice. A higher proportion of $CART^+$ cells in the cocaine-treated mice were present in the nucleus accumbens (NAc) shell than in the dorsolateral (DL) part of caudate putamen (CP). The concomitant administration of both $D_1R$ and $D_2R$ antagonists, SCH 23390 ($D_1R$ selective) and raclopride ($D_2R$ selective), blocked cocaine induced-behavioral sensitization, CART over-expression, and cyclic adenosine 5'-monophosphate (cAMP)/ protein kinase A (PKA)/phospho-cAMP response element-binding protein (pCREB) signal pathways. SCH 23390 more predominantly inhibited the locomotor activity, CART over-expression, pCREB and PKA activity than raclopride. Cocaine induced-behavioral sensitization was also attenuated in the both $D_1R$ and $D_2R$ knockout (KO) mice, respectively. CART over-expression and activated cAMP/PKA/pCREB signal pathways were inhibited in the $D_1R$-KO mice, but not in the $D_2R$-KO mice. It is suggested that behavioral sensitization, CART over-expression and activated cAMP/PKA/pCREB signal pathways induced by repeated administration of cocaine could be more predominantly mediated by $D_1R$.

• Toxicological Research
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• v.6 no.1
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• pp.75-88
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• 1990

The characteristics of dopamine uptake, D-1 and D-2 receptors after acute and subacute cocaine administration were determind in striatum from WKY and SHR. Cocaine was administered either acutely (40 mg/kg, s.c.) or twice daily (20 mg/kg, s.c.) for 3 and 7 days in 9-wk old WKY and SHR. Rats were sacrificed 30 min, 2 or 24 h after the single injection and 18 h after the last administration to the subacutely treated group. The changes in dopamine uptake, dopamine uptake sites, D-1 and D-2 receptors were determined using $(^3H)$dopamine, $(^3H)$-GBR-12935, $(^3H)$SCH-23390 and $(^3H)$sulpiride, respectively. In acutely treated rats, significant increases in $V_{max}$of dopamine uptake were observed 30 min after the cocanine injection in both strains without changes in $K_m$ values. The in vitro $IC_{50}$for cocaine was significantly decreased 30 min in WKY and 2 h in SHR. However, that for in vitro GBR-12909 was significantly increased 30 min and 2 h in both strains. Also densities of $(^3H)$-GBR-12935 binding sites were significantly increased 30 min and 2 h without changes in their $K_d$. Significant increases in D-2 receptor density were observed 30 min, 2 or 24 h after acute injection in both strains without changes in their affinities. The density of D-1 receptor was significantly decreased 30 min after the injection in WKY, but not in SHR. In subacutely treated rats, a significant increase in $K_m$ of dopamine uptake was observed in 7-day treated SHR. The in vitro $IC_{50}$fot GBR-12909 was significantly increased in 3-day treated WKY. The density of D-1 receptors was significantly increased in 3- and 7-day treated WKY, but not in SHR. The affinity of both binding sites remained unchanged. The results suggest that cocanine administration alters dopamine uptake, characteristics of dopamine uptake sites and dopamine receptor binding characteristics in rat brain. Furthermore, D-1 and D-2 dopamine receptors appear to be differently regulated.

• BMB Reports
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• v.43 no.4
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• pp.225-232
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• 2010

Parkinson's Disease (PD) is a common neurodegenerative disease characterized by the progressive degeneration of nigrostriatal dopaminergic (DA) neurons. Although the causative factors of PD remain elusive, many studies on PD animal models or humans suggest that glial activation along with neuroinflammatory processes contribute to the initiation or progression of PD. Additionally, several groups have proposed that dysfunction of the blood-brain barrier (BBB) combined with infiltration of peripheral immune cells play important roles in the degeneration of DA neurons. However, these neuroinflammatory events have only been investigated separately, and the issue of whether these phenomena are neuroprotective or neurotoxic remains controversial. We here review the current knowledge regarding the functions of these neuroinflammatory processes in the brain. Finally, we describe therapeutic strategies for the regulation of neuroinflammation with the goal of improving the symptoms of PD.

• BMB Reports
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• v.51 no.11
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• pp.590-595
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• 2018

Parkinson's disease (PD) is a common chronic neurodegenerative disease mainly caused by the death of dopaminergic neurons. However, no complete pharmacotherapeutic approaches are currently available for PD therapies. 1-methyl-4-phenylpyridinium $(MPP^+)$-induced SH-SY5Y neurotoxicity has been broadly utilized to create cellular models and study the mechanisms and critical aspects of PD. In the present study, we examined the role of a novel azetidine derivative, 3-(naphthalen-2-yl(propoxy)methyl)azetidine hydrochloride (KHG26792), against $MPP^+$-induced neurotoxicity in SH-SY5Y cells. Treatment of KHG26792 significantly attenuated $MPP^+$-induced changes in the protein levels of Bcl-2 and Bax together with efficient suppression of $MPP^+$-induced activation of caspase-3 activity. KHG26792 also attenuated mitochondrial potential and levels of ROS, $Ca^{2+}$, and ATP in $MPP^+$-treated SH-SY5Y cells. Additionally, KHG26792 inhibited the induced production of nitric oxide and malondialdehyde. Moreover, the protective effect of KHG26792 is mediated through regulation of glutathione peroxidase and GDNF levels. Our results suggest a possibility that KHG26792 treatment significantly protects against $MPP^+$-induced neurotoxicity in SH-SY5Y cells and KHG26792 may be a valuable therapeutic agent for the treatment of PD induced by an environmental toxin.

• Korean Journal of Biological Psychiatry
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• v.3 no.2
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• pp.262-268
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• 1996

It has been known that clozapine is more selective mesolimbic dopamin $D_2$ receptor antagonist and related to 5-HT receptor. In this study, we wxamined the plasma homovanillic acid(HVA), serotonin(5-HT), and 5-hydroxyindoleacetic acid(5-HIM) levels in refractory schizophrenics during clozapine treatment. And we assessed the effects of clozapine on these plasma monoamine metabolites and their association with psychopathology and treatment response. Eight refractory schizophrenic patients(DSM-IV) have entered the study for 3 months during clozapine treatment. Patients were admitted to the inpatient sevice and withdrawn from all neuroleptics for 7-14 days but exceptionally occasional doses of lorazepam was given if needed for behavioral control. The dose of clozapine was titrated as tolerated to 800mg/day. The plasma HVA. 5-HIM and 5-HT levels were measured before treatment and following 2nd week, 4th week, 8th week, and 12th during treatment. Psychopathology was assessed with Brief Psychiatric Rating Scale (BPRS) and Positive and Negative Synrome Scale(PANSS) before and during clozapine treatment. During clozapine treatment, no statistically significant changes were found in plasma HVA, 5-HIM, 5-HT levels, and HVA/5-HIM ratio between baseline and following 2nd week, 4th week, 8th week, 12th week. However, the change in plasma 5-HIAA/5-HT ratio from baseline to 4th week was statistically significant. Generally, changes of plasma HVA, 5-HIAA, 5-HT levels and HVA/5-HIAA ratio were not associated with psychopathology but 5-HIAA was associated with in positive symptoms and general psychopathology of PANSS. These results suggest that clozapine has been found to have relatively weak dopaminergic blokade and stronger serotonergic antagonism.

• Korean Journal of Biological Psychiatry
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• v.4 no.1
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• pp.95-101
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• 1997

The recent hypothesis about the pathophysiology of schizophrenia has been centered mainly on two theories, i.e. dopamine hypothesis and serotonin hypothesis. We investigate the correlations between plasma monoamine metabolite concentrations and clinical symptoms in schizophrenic patients. The first purpose of our study was to examine whether the plasma levels of HVA(homovanillic acid) and 5-HIAA(hydroxyindoleacetic acid) are significantly different in schizophrenics, compared to normal controls. And, with the intention of clarifying the interaction between dopaminergic system and serotoninergic system, the ratio of HVA/5-HIAA also was measured. The second purpose was whether the basal(pre-treatment) levels of these metabolites show the correlation with clinical symptoms. Finally, third purpose was whether basal HVA and 5-HIAA levels can be held as a predictor of treatment response. We used Scale for the Assessment of Positive Symptoms(SAPS) and Scale for the Assessment of Negative Symptoms(SANS) as the clinical symptom rating scales. Our results were as followed, 1) only the level of basal plasma HVA was significantly differ in schizophrenics. 5-HIAA and HVA/5-HIAA were not. 2) basal HVA showed significant correlation with SAPS score, especially delusion subscale. 3) the higher was the basal HVA level, the more improvement in clinical symptoms was observed. The basal 5-HIAA level and the HVA/5-HIAA ratio did not show any significant findings. These results support the dopamine hypothesis of schizophrenia, but fail to examine on the possible involvement of serotonin in schizophrenia.