多巴胺受体激动剂治疗帕金森病最新进展

本文综述了多巴胺受体激动剂在帕金森病(PD)治疗中的最新进展,介绍了培高利特(pergolide)、吡贝地尔(piribedil)、普拉克索(pramipexole)和罗匹尼罗(ropinirole)等药物对帕金森病运动症状的改善及其对多巴胺能神经元保护的作用。     

比较多巴胺和左旋多巴对大鼠肝脏芳基硫酸转移酶和雌激素硫酸转移酶的诱导作用（英文）

硫酸转移酶是主要的II相药物代谢酶之一。芳基硫酸转移酶包括rSULT1A1和rSULT1E1,能够催化酚类化合物发生硫酸化。多巴胺是中枢神经系统重要的神经递质,并且能调控各种外周功能。本研究旨在探究多巴胺和左旋多巴对大鼠肝脏硫酸转移酶（rSULT1A1,rSULT1E1）的作用。分别给予雄性大鼠、雌性大鼠不同浓度多巴胺（0,2,10,100 mg/kg/d）及左旋多巴（0,5,25,125 mg/kg/d）。采用real-time PCR以及western blot方法测定rSULT1A1和rSULT1E1的mRNA和蛋白表达;采用PNPS以及放射性的方法测定rSULT1A1和rSULT1E1活性。结果表明：多巴胺增加两种性别大鼠肝脏中rSULT1A1的表达和活性,而对rSULT1E1无显著作用;左旋多巴仅对雄性大鼠肝脏的rSULT1E1有诱导作用,但对两种大鼠肝脏中rSULT1A1以及雌性大鼠的rSULT1E1未产生显著作用。研究结果说明多巴胺在外周和中枢神经系统对rSULTA1和rSULTE1的诱导作用是不同的。     

大鼠多巴胺D1受体介导二氢埃托啡位置偏爱效应

AIM: To study the influence of dopamine (DA) receptor antagonists upon the rewarding property of dihydroetorphine (DHE). METHODS: Conditioned place preference (CPP) paradigm was used to characterize the rewarding effect of DHE. DA receptor antagonists were injected administered subcutaneously or peritoneally and microinjected into nucleus accumbens (NAcc). RESULTS: DHE (0.05, 0.5, and 5.0 micrograms.kg-1, s.c.) produced place preference (P < 0.01). Both the DA receptor antagonist haloperidol and the selective D1 receptor antagonist Sch-23390 attenuated the place preference produced by DHE (0.5 microgram.kg-1, s.c.). l-Sulpiride and spiperone, selective D2 receptor antagonists, had no such effects. CONCLUSION: The D1 (but not D2) receptors in NAcc are crucial in the mediation of the rewarding effect of DHE.     

多巴胺受体激动剂在延缓和治疗帕金森病相关运动并发症中的临床应用

本文从多巴胺受体激动剂的分类、作用机制和临床应用等方面综述多巴胺受体激动剂在延缓和治疗帕金森病相关运动并发症中的价值。     

多巴胺D1ξχχ受体基因多态性与精神分裂症相关性研究

目的探讨精神分裂症与多巴胺D1受体（DRD1）基因多态性之间的关联。方法应用聚合酶链反应扩增技术,对中国汉族75例精神分裂症患者（患者组）和70例正常组（对照组）PCR扩增产物多态性检测,并进行关联分析。结果①正常组与患者组等位基因频数分布无显著性差异（χ2=17．72,P〉0．05）;②在138bp等位基因片段中,女性患者相对男性患者及对照组有较高的分布频率。结论DRD,基因多态性与精神分裂症无显著性关联,但性别不同可能影响精神分裂症的易感性。     

长期给予大鼠盐酸多巴胺对多巴胺受体激动剂诱导的肾皮质cAMP蓄积…

AIM: To study the effects of long-term application of dopamine HCl (DA) on the functional changes of dopamine receptor subtypes coupled to adenyl cyclase in rat renal cortex. METHODS: cAMP levels were measured by radioimmunoassay as an index of dopamine receptor function. RESULTS: Injection of DA (30 mg.kg-1.d-1, i.p. 30 d) reduced the fenoldopam (Fen) (100 mumol.L-1)-induced increments of cAMP production from the control group of +1.26 +/- 0.04 to the DA-treated group of +0.63 +/- 0.22 nmol.min-1/g tissue and the propyl-butyl-dopamine (PBDA) (100 mumol.L-1)-induced decrements of cAMP production in the presence of Sch-23390 (Sch) from the control group of -0.38 +/- 0.18 to the DA-treated group of -0.11 +/- 0.08 nmol.min-1/g tissue with, however, comparable percentile changes for the 2 groups. Sch blocked both Fen- and PBDA-induced increase in cAMP production, while domperidone (Dom) blocked the decreasing effects of PBDA on cAMP accumulation in the presence of Sch. CONCLUSION: Long-term application of DA produced a marked "down regulation" of both DA1 and DA2 receptors in rat renal cortex with, however, the responsiveness of the remaining receptors unchanged.     

氯代斯阔任对多巴胺受体的作用

比较四氢原小檗碱同类物和氢化苄基－四氢异喹啉类两类化合物对ＤＡ受体的作用强度，从而找出对ＤＡ受体作用更有效的化合物。用小牛纹状体膜蛋白对Ｄ１和Ｄ２受体进行放射受体结合分析并进行大鼠行为实验。     

外周作用的多巴胺受体药物治疗应用进展

多巴胺(Dopamine,DA)属天然儿茶酚胺类,除能激动肾上腺素受体外,还能激动多巴胺受体(Dopamine Receptor,DAR)。在体内,它既是合成去甲肾上腺素的前体物,又是中枢神经系统黑质—纹状体通路及中脑—边缘系统的独立递质。它对外周心血管系统及肾脏的作用有别于去甲肾上腺素和肾上腺素;在小剂量时先激动 DAR,在剂量加大时才激动β—受体和α—受体。因此,在循环休克、充血性心衰及肾脏疾病中广为应用。现有资料表明,外周 DAR 可以分为 DA_1和 DA_2两个亚型。DA_1R 主要分布于肾脏、肠系膜、冠脉和脑等血管平滑肌(突触后膜)上,激动时引起上述血管扩张,外周阻力降低,局部血流增加;另外,DA_1R 还存在于肾小管     

Acute effects of styrene inhalation on the neuroendocrinological system of rats and the different effects in male and female rats

There have been several epidemiological and experimental studies about styrene from the neuroendocrinological viewpoint. Some reported that styrene exposure affected the neuroendocrinological system and enhanced prolactin (PRL) secretion, but others have denied those effects. It was assumed that styrene exposure caused depletion of dopamine (DA), which is a PRL inhibitor, and that, in consequence, the PRL level increased. However, not only DA but also many other factors control PRL secretion. Therefore, the mechanism of hypersecretion of PRL has not yet been clearly elucidated. In addition, effects of styrene on the female reproductive system have been reported, but the susceptibility needs to be further studied. Therefore, to investigate what causes hypersecretion of PRL and how different the susceptibility is in males and females, we studied acute effects of styrene exposure on the neuroendocrinological system in male and female rats. Immediately after exposure to 150 ppm styrene vapor for 10 days (8 h/day), male and female rats were killed, and blood and brain samples were collected. The styrene concentration in blood, hormones such as PRL, growth hormone (GH) and thyroid-stimulating hormone (TSH) in plasma and neurotransmitters in various brain regions were measured. The styrene concentration in the blood of female rats was higher than that in male rats, and the PRL level was significantly increased in female exposed rats compared with controls. No significant change was observed in male rats. We did not observe any significant changes in DA, 5-hydroxytryptamine (5-HT) or their metabolites. Because neurotransmitters were not affected in either male or female rats, the mechanism enhancing PRL secretion remains unclear. These results suggest that styrene exposure may cause hypersecretion of PRL and that the sensitivity to styrene exposure of the female may be higher than that of the male.     

Effects of subchronic exposure to styrene on the extracellular and tissue levels of dopamine, serotonin and their metabolites in rat brain

At present, there is controversy over the neurotoxic potential of styrene. Several epidemiological and clinical studies have shown that styrene exposure causes alterations of central nervous system functions in humans. Neurotransmitters have been implicated in the pathogenesis of styrene neurotoxicity in rodents. Several studies carried out on postmortem brain tissue suggest that styrene may alter dopaminergic neurotransmission in rabbit or rat brain. Moreover, in vitro studies suggest that both styrene and styrene oxide inhibit the uptake of dopamine (DA) in purified synaptic vesicles prepared from rat brain striata. To date, biochemical studies on animals have explored global tissue levels of neurotransmitters with sub-acute exposures to styrene. However, extracellular levels of neurotransmitters are more closely related to behaviour than are global tissue levels. The present study determined changes in the extracellular concentrations of DA, serotonin (5-HT) and their acid metabolites, dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxyindolacetic acid (5-HIAA), in striatal dialysates from freely moving adult male rats after exposure to 750 and 1,000 ppm styrene, 6 h per day, 5 days per week for 4 weeks. We also determined the concentrations of DA, 5-HT and their acid metabolites in striatum, nucleus accumbens and prefrontal cortex obtained postmortem from similarly exposed rats. Exposure to 1,000 ppm of styrene caused a significant decrease in extracellular acid metabolite concentrations. Tissue levels of acid metabolites were also decreased to a lesser extent. The effects were observed 72 h after discontinuing exposure but had vanished 17 days later. There was no change in DA or 5-HT concentrations either in the dialysates or tissues. Exposure to 750 ppm styrene caused no changes in the concentrations of DA, 5-HT and their acid metabolites either in the dialysates or tissues. The possibility that the effect of styrene is mediated by monoamine oxidase (MAO) inhibition is discussed.     

Regional alterations of brain catecholamines by styrene exposure in rabbits

The regional distribution of dopamine, norepinephrine and homovanillic acid was assessed in adult male rabbits exposed to styrene vapours. The turnover of dopamine and norepinephrine was also measured in several brain regions by the decay in endogenous catecholamines after inhibition of tyrosine hydroxylase by -methyl-p-tyrosine. Styrene exposure produced a marked and dose-dependent decrease in striatal and tuberoinfundibular dopamine, associated with a consistent increase in homovanillic acid content in the same regions. Norepinephrine levels were unaffected by styrene exposure. The observed increase in catabolism of dopamine cannot be explained by the turnover time, which was not significantly different in the exposed as compared to the control rabbits. Competition of a styrene metabolite with dopamine for the vesicular storage capacity or a selective destruction of dopaminergic terminals are suggested as the possible mechanisms for styrene neurotoxicity.     

In vitro kinetics of styrene and styrene oxide metabolism in rat,mouse, and human

Styrene oxide (SO), a labile metabolite of styrene, is generally accepted as being responsible for any genotoxicity associated with styrene. To better define the hazard associated with styrene, the activity of the enzymes involved in the formation (monooxygenase) and destruction of SO (epoxide hydrolase and glutathione-S-transferase) were measured in the liver and lungs from naive and styrene-exposed male Sprague-Dawley rats and B6C3F1 mice (three daily 6-h inhalation exposures at up to 600 ppm styrene) and Fischer 344 rats (four daily 6-h inhalation exposures at up to 1000 ppm styrene), and in samples of human liver tissue. Additionally, the time course of styrene and SO in the blood was measured following oral administration of 500 mg styrene/kg body weight to naive Fischer rats and rats previously exposed to 1000 ppm styrene. The affinity of hepatic monooxygenase for styrene, as measured by the Michaelis constant (K _m), was similar in the rat, mouse, and human. Based on theV _max for monooxygenase activity and the relative liver and body size, the mouse had the greatest capacity and humans the lowest capacity to form SO from styrene. In contrast, human epoxide hydrolase had a greater affinity (i. e., lowerK _m) for SO than epoxide hydrolase from rats or mice while the apparent Vmax for epoxide hydrolase was similar in the rat, mouse, and human liver. However, the activity of epoxide hydrolase relative to monooxygenase activity was much greater in the human than in the rodent liver. Hepatic glutathione-S-transferase activity, as indicated by theV _max, was 6- to 33-fold higher than epoxide hydrolase activity. However, the significance of the high glutathione-S-transferase activity is unknown because hydrolysis, rather than conjugation, is the primary pathway for SO detoxification in vivo. Human hepatic glutathione-S-transferase activity was extremely variable between individual human livers and much lower than in rat or mouse liver. Prior exposure to styrene had no effect on monooxygenase activity or on blood styrene levels in rats given a large oral dose of styrene. In contrast, prior exposure to styrene increased hepatic epoxide hydrolase activity 1.6-fold and resulted in lower (0.1>P>0.05) blood SO levels in rats given a large oral dose of styrene. Qualitatively, these data indicate that the mouse has the greatest capacity and the human the lowest capacity to form SO. In addition, human liver should be more effective than rodent liver in hydrolyzing low levels of SO. Quantitative evaluation of the species differences in enzyme levels are being evaluated with the development of a physiologically based pharmacokinetic model for styrene that includes SO.     

Effects of styrene and styrene oxide on glutathione-related antioxidant enzymes

Styrene is both hepatotoxic and pneumotoxic in mice. Its mode of action is not clear, but it may be related to oxidative stress including a very large decrease in reduced glutathione (GSH). The current studies evaluated if: (1) the more toxic R-styrene oxide had a greater effect on reduced GSH levels than the less toxic S-styrene oxide, (2) the ratio of reduced to oxidized forms of glutathione was altered by styrene or styrene oxide, (3) other enzymes involved in the oxidant status of the cell, namely glutathione reductase, glutathione peroxidase and gamma-glutamylcysteine synthetase were altered, and (4) lipid peroxidation, as measured by the determination of malondialdehyde, increased. R-Styrene oxide (300mg/kg, ip) caused greater decreases in mouse liver and lung GSH than did S-styrene oxide (300mg/kg, ip). Styrene (600mg/kg, ip) caused decreases in both GSH and GSSG in both liver and lung. Styrene and styrene oxide did not cause significant increases in lipid peroxidation in either liver or lung. Styrene and styrene oxide had minimal effects on glutathione reductase and glutathione peroxidase in liver and lung. Styrene increased gamma-glutamylcysteine synthetase activity. The results suggest that while styrene and its metabolite styrene oxide cause significant decreases in GSH levels, they have little effect on the enzymes glutathione reductase and glutathione peroxidase and that in response to decreased glutathione levels there is an increase in its synthesis via induction of gamma-glutamylcysteine synthetase activity.     

Effect of styrene administration on rat testis

Styrene was administered through gavage to adult male rats for 60 days. At the lower dose of 200 mg/ kg/day no overt signs of testicular toxicity were observed, while at the higher dose of 400 mg/kg/day activities of some marker enzymes for testicular function were found to be altered significantly, along with a decrease in spermatozoa number. Histopathological studies revealed marked degeneration of seminiferous tubules and lumen devoid of sperms, further confirming testicular toxicity of styrene. The present study suggests an overall sensitivity of the male reproductive system towards styrene exposure.     

Dopamine D1 receptor agonists induce penile erections in rats

The dopamine receptor agonist apomorphine has been recently introduced in the treatment of erectile dysfunction. While it is well established that dopamine D2-like receptors play a crucial role in this effect, conflicting result are reported in the literature as for the role of dopamine D1-like receptors. The aim of this study was to determine the effect of systemic administration of dopamine D1-like receptor agonists on penile erection in rats. Male Wistar rats were treated with three different, and not structurally related, dopamine D1-like receptor agonists: the partial agonists SKF38393 ((+) 2,3,4,5-tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-benzazepine) and CY 208-243 ((-)-4,6,6a,7,8,12b-exahydro-7-methylindole [4,3-ab]fenantridine), and the full agonist A 77636 ((-)-(1R,3S)-3-Adamantyl-1-(aminomethyl)-3,4-dihydro-5,6-dihydroxy-1H-2-benzopyran hydrochloride). All three compounds dose-dependently increased the number of penile erections, with the full agonist A77636 showing a more pronounced effect with respect to the other two. Moreover, the dopamine D1-like receptor antagonist SCH 23390 ((R)-(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine) dose-dependently antagonised A77636 effect. These results show that systemic administration of dopamine D1-like receptor agonists induce penile erection in rats. This observation suggests that dopamine D1-like receptor agonists might be considered as a possible alternative to apomorphine in the treatment of erectile dysfunction, thus avoiding the typical side effects related to the stimulation of dopamine D2-like receptors such as nausea.     

Comparison of the susceptibility of wild-type and CYP2E1 knockout mice to the hepatotoxic and pneumotoxic effects of styrene and styrene oxide

Styrene causes both liver and lung damage in non-Swiss albino, CD-1, and other strains of mice. This is considered to be due to the bioactivation of styrene to styrene oxide by cytochromes P450, principally CYP2E1 and CYP2F2. If so, one would expect CYP2E1 knockout mice to be less susceptible to styrene-induced toxicity than wild-type mice. However, previous in vitro and in vivo studies demonstrated little difference in the metabolism of styrene to styrene oxide between wild-type and CYP2E1 knockout mice. These findings would suggest that there should be no difference in the toxic responses to styrene between these two strains. To determine which of these possibilities was correct, styrene (600 mg/kg) or styrene oxide (300 mg/kg) was administered i.p. 24 h prior to measurement of serum sorbitol dehydrogenase as a biomarker of hepatotoxicity or lactate dehydrogenase activity, protein, and cells in bronchoalveolar lavage fluid as biomarkers for pneumotoxicity. Styrene was more hepatotoxic in the wild-type mice than in the knockout mice suggesting CYP2E1 activity is important. Strain differences were not observed with styrene oxide indicating no difference in intrinsic susceptibility. For lung, the response was similar in both strains to both styrene and styrene oxide supporting the idea that CYP2F2 is important in the bioactivation of styrene in this tissue and that there is no strain difference in susceptibility to the active metabolite.     

Structure-toxicity relationship study of para-halogenated styrene analogues in CYP2E1 transgenic cells

Styrene is one of the most important industrial intermediates consumed in the world and is mainly used as a monomer for reinforced plastics and rubber. Styrene has been found to be hepatotoxic and pneumotoxic in humans and experimental animals. The toxicity of styrene is suggested to be metabolism-dependent. Styrene-7,8-oxide has been considered as the major metabolite responsible for styrene-induced cytotoxicity. The objective of the study was to investigate the correlation between cytotoxicity of styrene and chemical and biochemical properties of the vinyl group of styrene by development of structure activity relationships (SAR). 4-Fluorostyrene, 4-chlorostyrene and 4-bromostyrene were selected for the SAR study. Cytotoxicity of styrene and the halogenated styrene derivatives with an order of 4-bromostyrene>4-chlorostyrene>4-fluorostyrene≈styrene was observed in CYP2E1 transgenic cells. Similar orders in the efficiency of the metabolism of styrene and the halogenated styrene analogues to their oxides and in the electrophilicity of the corresponding oxides were observed. Additionally, the order of the potency of cellular glutathione depletion and the degree of protein adduction induced by styrene and the halogenated styrenes were consistent with that of their cytotoxicities. The wild-type cells were less susceptible to the toxicity of the corresponding model compounds than CYP2E1 cells. The present study provided insight into the roles of the biochemical and chemical properties of styrene in its cytotoxicity.     

Levodopa and receptor sensitivity modification in tardive dyskinesia

Tardive dyskinesia (TD), a syndrome of involuntary hyperkinetic movements, purportedly involves the development of dopamine (DA) receptor hypersensitivity following long-term receptor blockade with neuroleptic drugs. It has been proposed that througn a process of receptor hypersensitivity modification, TD can be treated by reversing the receptor hypersensitivity with DA agonists. Thirteen patients with TD were treated for 4–8 weeks with levodopa plus benserazide, a peripheral decarboxylase inhibitor (Madopar, Roche, Basel, Switzerland) over a wide dose range corresponding to 3.0–9.0 g/day levodopa. Drug effects was assessed by blind evaluations of randomly sequenced videotapes made before, during, and for 6 weeks following treatment. TD scores moderately increased during levodopa. After the drug was discontinued, TD scores returned to pretreatment baseline levels without further improvement in those patients receiving concurrent neuroleptic medications (N=9), but in the neuroleptic-free patients TD scores decreased 25% in three patients and were resolved in one younger patient. Psychological effects of depression or increased psychotic symptoms occurred at higher drug doses. These results do not support the proposal that receptor sensitivity modification with levodopa is an effective therapeutic approach to TD, though selected patient and drug treatment variables, including other DA agonists, are considerations for further investigation.