• Molecules and Cells
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• 제25권2호
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• pp.149-157
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• 2008

Dopamine is a major neurotransmitter in the mammalian central nervous system (CNS) that regulates neuroendocrine functions, locomotor activity, cognition and emotion. The dopamine system has been extensively studied because dysfunction of this system is linked to various pathological conditions including Parkinson's disease, schizophrenia, Tourette's syndrome, and drug addiction. Accordingly, intense efforts to delineate the full complement of signaling pathways mediated by individual receptor subtypes have been pursued. Dopamine D1-like receptors are of particular interest because they are the most abundant dopamine receptors in CNS. Recent work suggests that dopamine signaling could be regulated via dopamine receptor interacting proteins (DRIPs). Unraveling these DRIPs involved in the dopamine system may provide a better understanding of the mechanisms underlying CNS disorders related to dopamine system dysfunction and may help identify novel therapeutic targets.

• Animal cells and systems
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• 제3권2호
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• pp.103-113
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• 1999

Many in-depth reviews related to regulations of prolactin secretion are available. We will, therefore, focus on controversial aspects using personal opinion in this review. The neuroendocrine control of prolactin secretion from the anterior pituitary gland involves multiple factors including prolactin-release inhibiting factor (PIF) and prolactin releasing factor (PRF). The PIF exerts a tonic inhibitory control in the physiological conditions. The PIF should be able to effectively inhibit prolactin release or a lifetime, but the inhibitory action of dopamine cannot be sustained for a long period of time. Perifusion of a high concentration of dopamine (l ,000 nM) could not sustain inhibitory action on prolactin release but when a small amount of ascorbic acid (0.1 mM) is added in a low concentration of dopamine (3 nM) solution, prolactin release was inhibited for a long period. Ascorbate is essential for dopamine action to inhibit prolactin release. We have, therefore, concluded that the PIF is dopamine plus ascorbate. The major transduction system for dopamine to inhibit prolactin release is the adenylyl cyclase system. Dopamine decreases cyclic AMP concentration by inhibiting adenylyl cyclase, and cyclic AMP stimulates prolactin release. However, the inhibitory mechanism of dopamine on prolactin release is much more complex than simple inhibition of CAMP production. The dopamine not only inhibits cyclic AMP synthesis but also inhibits prolactin release by acting on a link(s) after the CAMP event in a chain reaction for inhibiting prolactin release. Low concentrations of dopamine stimulate prolactin release. Lactotropes are made of several different subtypes of cells and several different dopamine receptors are found in pituitary. The inhibitory and stimulatory actions induced by dopamine can be generated by different subtype of receptors. The GH$_4$ZR$_7$ cells express only the short isoform (D$_{2s}$) of the dopamine receptor, as a result of transfecting the D$_{2s}$ receptors into GH$_4$C$_1$ cells which do not express any dopamine receptors. When dopamine stimulates or inhibits prolactin release in GH$_4$ZR$_7$ cells, it is clear that the dopamine should act on dopamine D$_{2s}$ receptors since there is no other dopamine receptor in the GH$_4$ZR$_7$. Dopamine is able to stimulate prolactin release in a relatively low concentration while it inhibits in a high concentration in GH$_4$ZR$_7$. These observations indicate that the dopamine D$_2$ receptor can activate stimulatory and/or inhibitory transduction system depending upon dopamine concentrations.

• Archives of Pharmacal Research
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• 제19권6호
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• pp.520-528
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• 1996

The involvement of the cyclic AMP (cAMP) effector system in the release of endogenous dopamine and acetylcholine from the rat neostriatum was assessed. Forskolin, an activator of adenylate cyclase, was used to enhance cAMP production, and the consequence of this enhancement on the spontaneous and potassium stimulated release of dopamine and acetylcholine was evaluated. Neostriatal slices were prepared from Fischer 344 rats and after a preincubation period the release of each endogenous neurotransmitter was measured from the same slice preparation. To measure acetylcholine release the slice acetylcholinesterase (AChE) activity was inhibited with physostigmine, but the release from slices with intact AChE activity was also determined (choline, instead of acetylcholine was detected in the medium). Under both conditions forskolin induced a significant dose-dependent increase in the potassium-evoked release of dopamine. In the same tissue preparations the release of neither acetylcholine (AChE inhibited) nor choline (AChE intact) was affected by forskolin. The results indicate that the CAMP second messenger system might be involved in neuronal mechanisms that enhance neostriatal dopamine release, but stimulation of this second messenger by forskolin does not further enhance neostriatal acetylcholine release.

• EDISON SW 활용 경진대회 논문집
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• 제2회(2013년)
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• pp.13-24
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• 2013

Dopamine agonists and antagonists and its receptor play a critical role in the information transfer in the nervous system, and dopamine receptor-ligands interactions are deeply related to Parkinson's disease, schizophrenia and some other mental diseases. However, the only experimental 3D structure available for dopamine receptors is human D3 dopamine receptor. Therefore, it is important to create model of subtype dopamine receptor-ligands interactions. We report here the 3D structures of the human D1 and D2 dopamine receptor predicted by using GalaxyTBM, and its predicted binding site determined by using GalaxyDock. The highly conserved Asp on TM 3 and Phe on TM 6 have critical role in ligand binding. Also, highly conserved serines on TM 5 are essential for binding agonists and some kinds of antagonists. We identify differences between binding sites of agonists and antagonists of human D1 and D2 dopamine receptor, and find the reasons of selective binding of antagonists.

• The Korean Journal of Physiology and Pharmacology
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• 제7권3호
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• pp.187-191
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• 2003

$Na^+/H^+$ exchanger (NHE) has a critical role in regulation of intracellular pH (pHi) in the renal proximal tubular cells. It has recently been shown that dopamine inhibits NHE in the renal proximal tubules. Nevertheless, there is a dearth of information on the effects of long-term (chronic) dopamine treatment on NHE activities. This study was performed to elucidate the pHi regulatory mechanisms during the chronic dopamine treatments in renal proximal tubular OK cells. The resting pHi was greatly decreased by chronic dopamine treatments. The initial rate and the amplitude of intracellular acidification by isosmotical $Na^+$ removal from the bath medium in chronically dopamine-treated cells were much smaller than those in control. Although it seemed to be attenuated in $Na^+$-dependent pH regulation system, $Na^+$-dependent pHi recovery by NHE after intracelluar acid loading in the dopamine-treated groups was not significantly different from the control. The result is interpreted to be due to the balance between the stimulation effects of lower pHi on the NHE activity and counterbalance by dopamine. Our data strongly suggested that chronic dopamine treatment increased intrinsic intracellular buffer capacity, since higher buffer capacity was induced by lower resting pHi and this effect could attenuate pHi changes under extracellular $Na^+$-free conditions in chronically dopamine-treated cells. Our study also demonstrated that intracellular acidification induced by chronic dopamine treatments was not mediated by changes in NHE activity.

• Archives of Pharmacal Research
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• 제14권2호
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• pp.109-113
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• 1991

Two types of aggressive behavior were produced by selective breeding in ICR mimce. NC900 line mice exhibited high level of species-typical, isolation-induced aggression, conversely, NC100 line mice exhibited little aggression. The present study tested the hypothesis that these differences involved brain monoamine systems. Comparisons of microdissected samples from various brain regions showed that NC100 line mice had significantly lower concentrations of dopamine. DOPAC and HVA in the nucleus accumbens (NAB) and caudate nucleus (NCU) than NC900 line. Homogenate binding studies demonstrated that NC100 mice had significantly increased density of $D_1$ dopamine receptor, but not $D_2$ dopamine receptor in the caudate nucleus. These results support the hypothesis that central dopamine pathways play an important role in modulating the genetically selected differences in aggressive behavior, and of which intensity differs from TEX>$D_1$\;and\;$D_2$ dopamine receptors.

• Journal of Yeungnam Medical Science
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• 제17권2호
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• pp.108-122
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• 2000

Background: Models of attention deficit hyperactivity disorder(ADHD) that have proposed a hypodopaminergic state resulting in hypofunction of the prefrontal circuitry have assumed a unitary dopamine system, which largely ignores the distinct functional differences between mesocortical dopamine system and nigrostriatal dopamine system. Purpose: The author's goal was to develop a pathophysiological model for ADHD with greater explanotory power than dopaminergic hypofunction hypothesis in prefronal circuitry. Material and Methods: Published clinical findings on ADHD were integrated with data from genetic, pharmacological, neuroimaging studies in human and animals. Results: Molecular genetic studies suggest that three genes may increase the susceptibility to ADHD. The three candidate genes associated with ADHD are each involved in dopaminergic function, and this consistent with the neurobiologic studies implicating catecholamines in the etiology of ADHD. Pharmacological data also provide compelling support for dopamine and noradrenergic hypothesis of ADHD. Neuroimaging studies lend substantial support for the hypothesis that right-sided abnormalities of prefrontal-basal ganglia circuit would be found in ADHD. Conclusions: The present hypothesis takes advantage of the major differences between the two pertinent dopamine systems. Mesocortical dopamine system, which largely lacks inhibitory autoreceptors, is ideally positioned to regulate cortical inputs, thus improving the signal-to-noise ratio for biologically valued signals. In this circuit, therapeutic doses of stimulants are hypothesized to increase postsynaptic dopamine effects and enhance executive functions. By contrast, symptoms of hyperactivity/impulsivity in ADHD are hypothesized to be associated with relative overactivity of nigrostriatal circuit. This nigrostriatal circuit is tightly regulated by inhibitory autoreceptoors as well as by long distance feedback from the cortex, and slow diffusion of therapeutic doses of stimulant via oral administration is hypothesized to produce a net inhibition of dopaminergic neurotransmission and improves hyperactivity.

• 약학회지
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• 제39권2호
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• pp.161-168
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• 1995

Brain dopamine systems play a central role in the control of movement, hormone release, and many complex behavior. The action of dopamine at its synapse is terminated predominately by high affinity reuptake into presynaptic terminals by dopamine transporter (DAT). The dopamine transporter(DAT) is membrane protein localized to dopamine-containing nerve terminals and closely related with cocaine abuse, Parkinsonism, and schizophrenia. In present study, the recombinant plasmid pRc/CMV-DAT, constructed by subcloning of a cDNA encoding a bovine DAT into eukaryotic expression vector pRc/CMV, was stably transfected into CV-1 cells(monkey kidney cell line). The DAT activities in the cell lines selected by Geneticin$^{R}$ were determined by measuring the uptake of $[^3H]$-dopamine. The transfected cell lines showed 30-50 fold higher activities than untransfected CV-1 cell line, and this result implies that DAT is well expressed and localized in transfected cells. The transfected cells accumulated $[^3H]$-dopamine in a dose-dependent manner with a $K_{m}$ of 991.6nM. Even though high doses of norepinephrine, epinephrine, serotonin, and choline neurotransmitters inhibited the uptake of $[^3H]$-dopamine, DAT in transfected cell line was proven to be much more specific to dopamine. The psychotropic drugs such as GBR12909, CFT, normifensine, clomipramine, desipramine, and imipramine inhibited significantly the dopamine uptake in tissue culture cells stably transfected with DAT cDNA. Radioactive in situ hybridization was done to map the cellular localization of DAT mRNA-containing cells in the adult rat central nervous system. The strong hybridization signals were detected only in the substantia nigra pars compacta and ventral tegmental area. The restricted anatomical localization of DAT mRNA-containing cells confirms the DAT as a presynaptic marker of dopamine-containing cells in the rat brain.

• The Korean Journal of Physiology
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• 제20권2호
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• pp.192-198
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• 1986

dopamine이 십이지장구를 포함한 소장의 운동성에 미치는 영향, cholecystokinin이 dopamine의 작용에 미치는 영향 그리고 이들 작용의 신경성 기전을 알아보고자 다음과 같은 실험을 실시하였다. ether로 마취한 토끼 54마리에서 십이지장구, 십이지장, 공장 그리고 회장을 적출하고 절편(길이 1cm)을 만들어 Krebs-Ringr 용액이 채워진 기록 용기에 넣고 자발적인 등장성 수축을 기록하였다. Krebs-Ringr 용액에는 5% $Co_2$를 함유하는 $O_2$를 계속 공급하였으며, 용액의 온도가 $37^{\circ}C$를 유지하도록 하였다. 자발적 수축이 시작하고 20분이 경과한 다음 dopamine($10^{-4}M$), CCK-8($10^{-8}M$), dopamine($10^{^6}M$)등을 투여하면서 수축성을 관찰하여 다음과 같은 결과를 얻었다. 1) dopamine은 소장의 모든 부위에서 자발적 수축성을 억제하였으며, 이러한 dopamine의 작용은 회장을 제외한 다른 부위에서 tetrodotoxin에 의하여 유의하게 감소하였다. 2) domperidone은 소장의 모든 부위에서 dopamine의 억제작용에 길항적으로 작용하였으며, tetrodotoxin을 전처치하면 회장을 제외한 다른 부위에서 domperidone의 길항작용은 완전히 소실되었다. 3) CCK-8는 소장의 모든 부위에서 dopamine의 작용을 감소시켰으며, tetrodotoxin을 전처치하면 CCK-8의 작용은 유의하게 감소되었다. 이상의 결과로 미루어 보아 dopamine은 십이지장구를 포함한 모든 소장의 수축성을 억제하며, CCK-8는 dopamine의 억제 작용을 감소시키는데, 이러한 작용들은 장관내 신경계를 거쳐서 간접적으로 일어나는 것으로 생각된다.

• 대한약리학회지
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• 제27권1호
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• pp.7-12
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• 1991

쥐(태령 14일) 뇌간 세포배양에서 발달과정에 따른 Tyrosine hydroxylase(TH) 활성 및 dopamine의 양적 증가를 전기화학 HPLC를 이용하여 측정하였다. TH 활성 및 dopamine의 양은 배양 7일까지 점차 증가하였다. 배양 7일째에 여러 약물들의 dopamine 대사에 대한 영향을 조사하였다. TH 억제제인 ${\alpha}-methyl-p-tyrosine$ 및 aromatic amiono acid decarboxylase 억제제인 NSD-1015는 효과적으로 dopamine을 고갈시켰다. Dopamine은 reserpine에 의해 고갈되었고, parglyine에 의해 증가되었다. 일주일 배양한 세포의 배양액에 tetrodotoxin$(0.1\;{\mu}M$)을 7일간 투여하였을 때 TH 활성은 현저히 감소하였다. 이상의 결과들은 배양세포의 dopamine 대사가 뇌 dopamine 대사를 충실히 반영함을 나타낸다. 뇌간 세포의 배양에서 HPLC-전기화학검출을 이용한 TH 활성 및 dopamine의 측정은 중추 dopamine계의 약리 및 독성 연구에 유용하리라 사료된다.