6-羟多巴胺纹状体内注射制作大鼠帕金森病模型的研究

目的 为拓宽6-OHDA损毁多巴胺能神经元所制备大鼠帕金森病模型的应用范围,采用多位点纹状体内注入6-OHDA的途径来制备模型。方法 研究用SD大鼠,两个针道内四点定位注射,每点注射3μg／μ16-OHDA3μl。结果 术后两周出现缓慢旋转,4周旋转行为达到7转／分并保持稳定;形态学染色可见损毁1周后注射侧黑质酪氨酸羟化酶免疫组化阳性细胞减少20％,2周后减少38％,3～4周减少70％以上,6周后损伤趋缓。高效液相-电化学法活体检测纹状体内多巴胺的代谢产物3、4-二羟基苯乙酸(DOPAC)和高香草酸(HVA),发现注射侧和非注射侧相比含量分别下降98．33％和96．05％;组织匀浆检测损毁侧黑质多巴胺含量下降了73％以上,3、4-二羟基苯乙酸(DOPAC)含量下降60％。结论 纹状体内注射6-OHDA能够制备帕金森病大鼠模型。     

阴虚动风证帕金森病异动症模型大鼠的氧化应激反应及复方地黄方的干预作用

目的探讨阴虚动风证帕金森病异动症(LID)大鼠氧化应激反应及复方地黄方的干预作用。方法采用6-羟基多巴胺(6-OHDA)偏侧损毁黑质制备帕金森病大鼠模型,进一步腹腔注射左旋多巴+苄丝肼(50 mg/kg左旋多巴和12.5 mg/kg苄丝肼)制备阴虚动风证帕金森病LID大鼠模型,并随机分为LID组、复方地黄方组,另取正常对照组、假手术组大鼠。每组6只。分别在4周、6周后进行神经行为学检测后,取纹状体,应用比色法分别测定各组大鼠纹状体内SOD、MDA、GSH、GSH-Px的含量。结果阴虚动风证帕金森病LID模型组大鼠纹状体内SOD、GSH、GSH-Px的含量均明显的减少,MDA的含量呈增加的趋势;而复方地黄方组大鼠纹状体内SOD、GSH、GSH-Px的含量均呈现增加的趋势,且随治疗时间的延长增加趋势更明显,MDA的含量呈现减少的趋势,且随治疗时间的延长减少的趋势更明显。结论复方地黄方较好地改善阴虚动风证LID大鼠的氧化应激反应,复方地黄方干预LID模型大鼠可能是通过清除自由基,减轻对细胞的损伤从而缓解帕金森病LID的症状。     

胎脑黑质脑内移植矫正PD鼠纹状体内脑啡肽mRNA过度表达

用６－ＯＨＤＡ损毁大鼠一侧黑质—纹状体通路可引起ＰＤ模型鼠脑纹状体内多巴胺匿乏．同时,亦可导致脑啡肽ｍＲＮＡ过度表达。我们用地高辛标记的ｃＲＮＡ探针对纹状体内脑啡肽ｍＲＮＡ含量进行了斑点杂交定量研究,发现损伤侧脑啡肽ｍＲＮＡ含量较健侧增高８０％,胎中脑移植到失神经支配的纹状体内,脑啡肽ｍＲＮＡ过度表达得以矫正至正常水平,说明胎多巴胺能神经元脑内移植能够调节脑啡肽基因表达,提供了移植物能与宿主发生神经整合、建立突触联系的间接证据。     

BDNF基因工程细胞对帕金森大鼠纹状体多巴胺及其代谢物影响的研究

目的:观察经侧脑室移植pIRESneo-EGFP-BDNF修饰骨髓间充质干细胞(MSCs)对帕金森病(PD)大鼠纹状体多巴胺(DA)及代谢产物的影响。方法:采用电穿孔法将pIRESneo-EGFP-BDNF转染至骨髓MSCs;制备PD大鼠模型,随机分为Sham组,PD组,MSCs组,脑源性神经生长因子(BDNF)组,经侧脑室移植MSCs或pIRESneo-EGFP-BDNF修饰骨髓MSCs,术后2周,4周,8周,腹腔注射阿朴吗啡(APO)诱导PD大鼠旋转行为;应用高效液相色谱测定各组大鼠纹状体内多巴胺(DA)、高香草酸(HVA)及二羟苯乙酸(DOPAC)。结果:移植术后2周,4周,8周BDNF组、MSCs组大鼠与PD组比较旋转次数明显减少(P<0.05),以BDNF组改善更为明显。移植细胞干预PD模型8周后BDNF组、MSCs组大鼠纹状体DA、HVA、DOPAC较PD组明显提高(P<0.01),以BDNF组更为显著。结论:经侧脑室移植pIRESneo-EGFP-BDNF修饰的骨髓MSCs干预PD大鼠模型,显著降低PD大鼠纹状体内DA代谢率,提高DA水平,改善PD大鼠的行为能力。     

海马多巴胺D1受体激活抑制谷氨酸介导的大鼠慢性应激性抑郁

本文旨在探讨在慢性应激性抑郁发生过程中多巴胺D1受体对谷氨酸及其离子型受体的影响。实验通过建立慢性不可预见性温和应激(chronic unpredictable mild stress,CUMS)抑郁模型,结合海马微量注射多巴胺D1受体激动剂SKF38393、非竞争性N-甲基-D-天冬氨酸(N-methyl-D-aspartic acid,NMDA)受体拮抗剂MK-801和α-氨基羟甲基异恶唑丙酸(α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid,AMPA)受体的拮抗剂NBQX,运用糖水偏爱测试、旷场实验和悬尾实验等方法检测动物的行为表现,采用高效液相色谱法(high-performance liquid chromatography,HPLC)和Western blot实验来检测海马内谷氨酸含量及其离子型受体关键亚基的表达。结果显示,与对照组相比,CUMS组大鼠表现出明显的抑郁样行为变化,且海马谷氨酸含量升高,其NMDA受体的NR1亚基与AMPA受体的GluR2/3亚基也明显下调;注射SKF38393后可明显改善应激引起的抑郁样行为,且海马谷氨酸含量显...     

不同剂量鱼藤酮对拟帕金森病模型大鼠行为学及纹状体多巴胺含量的影响

目的观察不同剂量鱼藤酮皮下注射对大鼠行为学及脑纹状体多巴胺含量的影响,探讨鱼藤酮拟帕金森病大鼠模型的适宜造模条件。方法Lewis大鼠分别给予鱼藤酮不同剂量（1．0、1．5和2．0ms／ks／d）皮下注射共28d。应用旷场实验和斜板实验分别测定大鼠的运动功能和协调性,高效液相色谱一电化学法检测大鼠纹状体内多巴胺含量。结果模型组大鼠存活率随鱼藤酮注射剂量的升高呈逐渐下降趋势。鱼藤酮2．0mg／kg组大鼠体重最先明显降低,随着注射时间的延长,各模型组大鼠均出现显著的体重降低。旷场实验结果显示,各剂量鱼藤酮组大鼠跨格次数和站立次数均明显下降。斜板实验结果显示,鱼藤酮1．5mg／kg组大鼠在斜板的停留角度较对照组显著减小。鱼藤酮I．5ms／kg组大鼠脑纹状体内多巴胺含量显著降低。结论鱼藤酮1．5ms／kg皮下注射28d,大鼠出现明显的运动功能障碍和脑内多巴胺含量减少,而死亡率相对较低,因此是建立帕金森病大鼠模型的适宜剂量。     

眶额叶区5-HT与Glu、NO在急性强迫游泳应激抑郁症模型中的关系

目的：探讨眶额叶区5-羟色胺（5-HT）与谷氨酸（Glu）、一氧化氮（N0）在急性强迫游泳应激抑郁症模型中的相互作用。方法：雄性SD大鼠随机分为对照组及各种药物注射组,强迫游泳制造大鼠应激性抑郁模型,眶额叶区微量注射各组药物,敞箱实验及游泳测试观察大鼠的抑郁样行为表现。结果：①与对照组比,注射Glu使大鼠强迫游泳不动时间显著增加;注射NMDA受体拮抗剂（MK-801）使大鼠强迫游泳不动时间减少;与Glu组比,MK-801预注射后Glu注射使大鼠强迫游泳不动时间减少;②与5-HT组比,MK-801预注射后5-HT注射使大鼠强迫游泳不动时间增加;③与对照组比,注射L-精氨酸（L-Ars）使大鼠强迫游泳不动时间显著增加;注射NOS抑制剂（L-NAME）（10μg/μl）使大鼠强迫游泳不动时间减少;L-NAME（20μg／μl）注射使大鼠强迫游泳不动时间增加;L-NAME（40μg/μl）注射使大鼠强迫游泳不动时间增加;④与L-NAME（10μg/μl）组比较,5-HT1A受体拮抗剂spipemne预注射后LNAME（10μg／μl）注射使大鼠强迫游泳不动时间增加。结论：眶额叶（OFC）区Glu含量的增加能够诱发抑郁,其作用可能主要是通过NMDA受体实现的,Glu经NMDA受体引发抑郁的同时还可能通过调节突触后膜上5-HT1A受体减弱5-HT的抗抑郁作用;OFC区NO可通过调节5-HT神经元进而参与抑郁的发生。     

阴虚动风证帕金森病异动症大鼠大麻素CB1受体变化及复方地黄方的干预作用

目的探讨阴虚动风证帕金森病(PD)异动症(LID)大鼠纹状体内大麻素CB1受体的表达及复方地黄方的干预作用。方法采用6-羟基多巴胺(6-OHDA)偏侧损毁黑质制备帕金森病大鼠模型,进一步腹腔注射左旋多巴+苄丝肼(50 mg/kg左旋多巴和12.5 mg/kg苄丝肼)制备LID大鼠模型,并随机分为LID组、复方地黄方组,另取正常对照组、假手术组大鼠为对照,每组6只。分别在4周、6周进行神经行为学检测后,处死大鼠并取纹状体,应用Western blot法测定各组大鼠纹状体内大麻素CB1受体的表达情况。结果 LID大鼠随造模时间延长,AIM评分呈增加趋势(P0.05),旋转启动时间呈缩短趋势(P0.05),旋转持续时间呈增加趋势(P0.01),剂峰旋转圈数呈减少趋势(P0.05),复方地黄方可改善上述变化。LID大鼠大麻素CB1受体表达增加,且随造模时间延长呈现减少趋势(P0.01),而复方地黄方干预后大麻素CB1受体的表达呈现逐渐增加的趋势(P0.01)。结论LID模型大鼠大麻素CB1受体的含量明显升高,其变化能够较好的反映阴虚动风证的严重程度,复方地黄方干预LID模型大鼠可能是通过激活纹状体内大麻素CB1受体,抑制兴奋性氨基酸(主要是谷氨酸)的释放和诱导细胞发生级联反应来减弱神经元的兴奋性,从而起到减轻L-dopa的兴奋毒性的作用。     

帕金森大鼠黑质和纹状体BMP4及其mRNA表达的时程变化

目的：探讨帕金森（PD）大鼠模型体内脑黑质和纹状体内骨形成蛋白4（BMP4）及其mRNA表达的变化规律。方法：用六羟基多巴胺（6-OHDA）建立PD模型后,第2、4、6、8和10周时处死大鼠,取左侧黑质、纹状体,用免疫组化、酶联免疫、荧光定量PCR技术从蛋白水平和基因水平检测BMP4及其mRNA表达。结果：BMP4及其mRNA表达基本一致,其BMP4及mRNA表达均呈双峰,其蛋白表达在纹状体内第2周和6周时达高峰、在黑质内第2周和8周时达高峰,其mRNA表达在纹状体内第2周和8周时达高峰、在黑质内第4周和8周达高峰,差异均有统计学意义（P〈0.05）。结论：PD大鼠模型体内,BMP4及其mRNA不呈现稳定的低表达,而是有波动性,明确BMP4及其mRNA处于稳定低表达的时间后,为下一步的治疗实验时间点的选择上奠定了基础。     

力竭运动及恢复期大鼠纹状体5-HT、DA及其代谢物浓度的动态变化研究

目的:观察一次性力竭运动过程及恢复期大鼠纹状体细胞外液中多巴胺(DA)和5-羟色胺(5-HT)及其代谢物浓度的动态变化规律。方法:采用活体微透析结合毛细管电泳-激光诱导技术,连续观察清醒大鼠在一次性力竭运动过程及恢复期纹状体细胞外液中酪氨酸(Tyr)、5-HT、5-羟吲哚乙酸(5-HIAA)、色氨酸(Trp)和DA浓度的动态变化。结果:大鼠纹状体细胞外液中Trp、5-HT、5-HIAA水平运动初期均未见显著变化(P>0.05),运动后期、力竭及恢复期均显著高于安静水平(P<0.05,P<0.01);DA、Tyr水平在运动后期、力竭及恢复期显著高于安静水平(P<0.05,P<0.01);DA/5-HT运动初期显著升高(P<0.05,P<0.01),运动后期出现下降趋势,力竭前15 min降至最低点,而恢复期略有回升,但运动后期、力竭及恢复期与安静状态相比均无显著差异。结论:力竭运动过程中大鼠纹状体细胞外液中DA和5-HT的动态变化具有阶段性特征,运动疲劳过程中状体内DA和5-HT两种神经递质的代谢水平均显著增强,而其中以5-HT的作用占优。     

Study by the intracerebral microdialysis method of the effects of atypical neuroleptics and anxiolytics on striatal release and metabolism of dopamine in awake rats]

Using brain microdialysis in awake rats effects of risperidone, ritanserin, buspirone, sulpiride and 5-methoxy-N,N-dimethyltryptamine (MeODMT) on striatal dopamine (DA) release and metabolism were studied. Risperidone, sulpiride and buspirone increased levels of DA, dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA). Ritanserin failed to affect DA release, while increased DOPAC and HVA levels. MeODMT had no effect on striatal DA release and metabolism. Possible interaction between DA and serotonin systems is discussed.     

Systemic administration of d-amphetamine induces long-lasting oxidative stress in the rat striatum

The long-term effect of d-amphetamine (AMPH) on the induction of oxidative stress was examined in vivo in the rat brain. In this study, 2,3-dihydroxybenzoic acid (2,3-DHBA) and malonaldehyde (MDA) were used as the index of the hydroxyl radical and lipid peroxidation, respectively. The levels of 2,3-DHBA, MDA and dopamine (DA) in striatal homogenates were examined 7 days following injection of a single large dose of AMPH (7.5 mg/kg, i.p.) in rats pretreated with desipramine (10 mg/kg, i.p.), an agent that inhibits the metabolism of AMPH. Our results showed that 2,3-DHBA and MDA levels were significantly increased by AMPH, whereas DA and its metabolites, DOPAC and HVA were depleted in the striatum. Pretreatment with the glutamate NMDA receptor subtype antagonist MK-801 (1 mg/kg, i.p.) attenuated the increases of 2,3-DHBA and MDA, and provided partial protection against the long-lasting loss of DA produced by AMPH. Overall, the results demonstrate that AMPH could induce sustained production of free radical and oxidative damage, and lead to DA terminal degeneration in the striatum of the rat.     

Intracerebral dialysis: direct evidence for the utility of 3-MT measurements as an index of dopamine release

Intracerebral dialysis was used to monitor the in vivo efflux of striatal dopamine (DA), homovanillic acid (HVA), dihydroxyphenylacetic acid (DOPAC) and 3-methoxytyramine (3-MT) in the pentobarbital anesthetized rat. In untreated rats, there were low levels of extra-cellular DA and 3-MT which were increased 15-fold by treatment with amphetamine. Under basal and drug-stimulated conditions, 3-MT concentrations were maintained at approximately 30% of the extracellular DA levels. These data agree with in vivo turnover estimates which indicate that 20 to 30% of DA turnover is through the 3-MT pool in the striatum. In contrast, extracellular DOPAC and HVA levels were reduced only slightly by amphetamine and with a delayed onset. Our data support the hypothesis that striatal DOPAC is an accurate index of intraneuronal DA metabolism and that 3-MT is an index of the extracellular concentration of DA.     

Influence of Selective Inhibition of Monoamine Oxidase A or B on Striatal Metabolism of l-DOPA in Hemiparkinsonian Rats

Abstract: The effect of selective inhibition of monoamine oxidase (MAO) subtypes A and B on striatal metabolism of DOPA to dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), and 4-hydroxy-3-methoxyphenylacetic acid (homovanillic acid; HVA) was studied in halothane-anesthetized rats 3 weeks after unilateral 6-hydroxydopamine lesion of the substantia nigra. Implantation of bilateral microdialysis probes allowed simultaneous quantitation of metabolite production on lesioned and control sides. The DOPA was administered as a 15-min bolus of 1 m M solution in the striatal microdialysate. Rats were pretreated with the selective MAO-A inhibitor clorgyline, or the selective MAO-B inhibitors deprenyl or TVP-101 [2,3-dihydro- N -2-propynyl-1 H -inden-1-amine-(1 R )-hydrochloride]. Intrastriatal infusion of DOPA caused an increased efflux of DA, DOPAC, and HVA, which was greater on the intact side. Clorgyline, but not deprenyl or TVP-101, increased post-DOPA DA efflux on both intact and lesioned sides. Clorgyline also caused a marked suppression of post-DOPA DOPAC and HVA effluxes, whereas only mild effects were produced by the MAO-B inhibitors. There was no evidence for a differential effect of MAO-B inhibition on efflux of DA or metabolites in the lesioned as compared with the control striatum. The results indicate a major role for MAO-A in DA metabolism both intra- and extraneuronally in the rat striatum.     

Enhancement of Brain Dopamine Metabolism by Tyrosine During Immobilisation: An In Vivo Study Using Repeated Cerebrospinal Fluid Sampling in Conscious Rats

Central dopamine (DA) and 5-hydroxytryptamine (5-HT) metabolism was monitored in conscious, freely moving rats by determination of levels of the DA metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) and the 5-HT metabolite 5-hydroxyindoleacetic acid (5-HIAA) in CSF samples withdrawn repeatedly from the cisterna magna and treated with acid to hydrolyse DOPAC and HVA conjugates. The effect of tyrosine on DA metabolism was investigated. Time courses of metabolite concentrations in individual rats in a quiet room showed that tyrosine (20, 50, or 200 mg/kg i.p.) was without significant effect; brain changes were essentially in agreement. However, the increases of CSF DOPAC and HVA levels that occurred on immobilisation for 2 h were further enhanced by tyrosine (200 mg/kg). The associated increases of 5-HIAA level were unaffected. The corresponding increases of DA metabolite concentrations in the brains of immobilised rats given tyrosine were less marked than the CSF changes and only reached significance for "rest of brain" DOPAC. The CSF studies revealed large interindividual variation in the magnitude and duration of the effects of immobilisation on transmitter amine metabolism. These results may help toward the elucidation of possible relationships between the neurochemical and behavioural effects of stress.     

Effect of Theanine,r-Glutamylethylamide,on Brain Monoamines and Striatal Dopamine Release in Conscious Rats

Theanine, r-glutamylethylamide, is one of the major components of amino acids in Japanese green tea. Effect of theanine on brain amino acids and monoamines, and the striatal release of dopamine (DA) was investigated. Determination of amino acids in the brain after the intragastric administration of theanine showed that theanine was incorporated into brain through blood-brain barrier via leucine-preferring transport system. The concentrations of norepinephrine, 3,4-dihydroxyphenylacetic acid (DOPAC) and 5-hydroxyindole acetic acid (5HIAA) in the brain regions were unaffected by the theanine administration except in striatum. Theanine administration caused significant increases in serotonin and/or DA concentrations in the brain, especially in striatum, hypothalamus and hippocampus. Direct administration of theanine into brain striatum by microinjection caused a significant increase of DA release in a dose-dependent manner. Microdialysis of brain with calcium-free Ringer buffer attenuated the theanine-induced DA release. Pretreatment with the Ringer buffer containing an antagonist of non-NMDA (N-methyl-D-aspartate) glutamate receptor, MK-801, for 1 hr did not change the significant increase of DA release induced by theanine. However, in the case of pretreatment with AP-5, (±)-2-amino-5-phosphonopentanoic acid; antagonist of NMDA glutamate receptor, the theanine-induced DA release from striatum was significantly inhibited. These results suggest that theanine might affect the metabolism and/or the release of some neurotransmitters in the brain, such as DA.     

Methamphetamine-elicited alterations of dopamine- and serotonin-metabolite levels within μ-opioid receptor knockout mice: a microdialysis study

μ-Opioid receptors (μ-ORs) modulate methamphetamine (MA)-induced behavioral responses, increased locomotor activity and stereotyped behavior in the mouse model. We investigated the changes in dopamine (DA) and serotonin (5-HT) metabolism in the striatum following either acute or repeated MA treatment using in vivo microdialysis. We also studied the role of μ-ORs in the modulation of MA-induced DA and 5-HT metabolism within μ-OR knockout mice. Subsequent to either acute or repeated intraperitoneal administration of MA, wild-type mice revealed decreases in extracellular concentrations of 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), and 5-hydroxyindoleacetic acid (5-HIAA) in a dose-dependent manner. Moreover, wild-type mice had reductions in basal concentrations of DOPAC and HVA following repeated MA treatment with a higher dose. The effects of acute, repeated or challenge MA administration upon extracellular levels of DOPAC and HVA within μ-OR knockout mice significantly differed from the wild-type controls. The duration of recovery to the basal levels of extracellular DA and 5-HT metabolites induced by MA were much longer in wild-type mice than for μ-OR knockout mice. These findings suggest that μ-ORs play a modulatory role in MA-induced DA and 5-HT metabolism in the mouse striatum. This possible mechanism of MA-induced behavioral change as modulated by μ-OR merits further study.     

The influence of substance P central administration on ethanol intake in rats chronically exposed to alcohol

The influence of central substance P (SP) administration on alcohol intake and brain dopamine metabolism within mesocortico-limbic and nigrostiatal systems of rats exposed to ethanol, was studied. During 6 months, the rats consumed 15% ethanol solution instead of water. Central administration of SP (3 mcg/kg) decreased alcohol consumption by 41% in alcohol-preference animals. After long-term ethanol exposure ratios DOPAC/DA and HVA/DA were reduced in striatum and accumbens. SP in dose 3 mcg/kg increased content of DOPAC by 17% and HVA by 23% as well as DOPAC/DA by 9%, HVA/DA by 19% in accumbens. Whereas in striatum only increased DOPAC (28%) and HVA (29%) were observed as compared with saline-treated rats.     

Endogenous Glutamate Increases Extracellular Concentrations of Dopamine, GABA, and Taurine Through NMDA and AMPA/Kainate Receptors in Striatum of the Freely Moving Rat: A Microdialysis Study

Abstract: Interactions between glutamate (Glu), dopamine (DA), GABA, and taurine (Tau) were investigated in striatum of the freely moving rat by using microdialysis. Intrastriatal infusions of the selective Glu uptake inhibitor l - trans -pyrrolidine-3,4-dicarboxylic acid (PDC) were used to increase the endogenous extracellular [Glu]. Correlations between extracellular [Glu] and extracellular [DA], [GABA], and [Tau], and the effects of a selective blockade of ionotropic Glu receptors, were studied. PDC (1, 2, and 4 m M ) produced a dose-related increase in extracellular [Glu]. At the highest dose of PDC, [Glu] increased from 1.55 ± 0.35 to 6.11 ± 0.88 µ M . PDC also increased extracellular [DA], [GABA], and [Tau]. The increasing [Glu] was correlated significantly with increasing [DA], [GABA], and [Tau]. PDC also decreased extracellular concentrations of DA metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and 4-hydroxy-3-methoxyphenylacetic acid (HVA). Perfusion with the NMDA-receptor antagonist 3-[( R )-2-carboxypiperazin-4-yl]-propyl-1-phosphonic acid (1 m M ) or the AMPA/kainate-receptor antagonist 6,7-dinitroquinoxaline-2,3-dione (DNQX) (1 m M ) attenuated the increases produced by PDC (4 m M ) on [DA], [GABA], and [Tau], and decreases in [DOPAC] and [HVA]. DNQX also attenuated the increases in [Glu] induced by PDC. These data show that endogenous Glu plays a role in modulating the extracellular concentrations of DA, GABA, and Tau in striatum of the freely moving rat.     

Effects of Catechol-O-Methyltransferase Inhibitors and L-3,4-Dihydroxyphenylalanine With or Without Carbidopa on Extracellular Dopamine in Rat Striatum

Abstract: The effects of two new catechol- O -methyltransferase (COMT) inhibitors, OR-611 and Ro 40-7592, in combination with L-3,4-dihydroxyphenylalanine (L-dopa) with or without carbidopa on extracellular levels of dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), 3- O -methyldopa (3-OMD), and 5-hydroxyindoleacetic acid in rat striatum were studied. A dose of 10 mg/kg i.p. of Ro 40-7592 alone, in contrast to the same dose of OR-611, decreased the dialysate level of HVA and increased that of DOPAC; this dose was thus used to differentiate between the effects of central and peripheral COMT inhibition. L-Dopa (50 mg/kg i.p.) alone slightly increased extracellular levels of DA, DOPAC, and HVA. The effects of L-dopa were potentiated by carbidopa (50 mg/kg i.p.), and even 3-OMD levels in dialysate samples became detectable. Both OR-611 and Ro 40-7592 significantly further increased the DA and DOPAC efflux from striatum produced by L-dopa. This increase was more pronounced when carbidopa was added to the treatment. OR-611 did not modify the effect of L-dopa or carbidopa/L-dopa on dialysate HVA levels, whereas Ro 40-7592 markedly reduced those levels. Both OR-611 and Ro 40-7592 very clearly suppressed dialysate 3-OMD levels produced by carbidopa/L-dopa. Ro 40-7592 was more effective than OR-611 in potentiating the effects of L-dopa or carbidopa/L-dopa. These in vivo data show that the new COMT inhibitors markedly inhibit the O -methylation of L-dopa and increase its availability to brain, which is reflected as increased DA formation. A significant effect can be achieved even by inhibiting only the peripheral COMT activity. The data suggest that COMT inhibitors may be of clinical importance as adjuncts in the treatment of Parkinson's disease.