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。     

帕金森病模型大鼠脑内多巴胺与铁含量的关系

实验采用原子吸收分光光度法,快速周期伏安法,高效液相电化学检测等方法,研究以6－羟基多巴（6－OHDA）制备的帕金森病（PD）模型大鼠黑质内铁含量的变化。铁对多巴胺（DA）能神经元的直接毒性作用以及铁离子螯合剂甲磺酸去铁胺的神经保护作用。结果发现：（1）PD大鼠损毁侧黑质内铁含量为非标准PD大鼠的3倍左右;（2）PD大鼠损毁侧纹状体内铁含量无明显改变;（3）单纯注射6－OHDA的大鼠其损毁侧纹状体（CPu)DA的释放量和含量均明显降低;（4）侧脑室预先注射甲磺酸去铁胺,再重复上述实验,损毁侧CPu DA释放量和含量均无明显改变;（5）单侧黑质内注射40ug FeCl3后,大鼠损毁侧CPu内DA释放量和含量显著降低。上述结果提示,6－OHDA可导致CPu DA释放量及含量减少,此过程有铁的参与。由于铁可导致DA神经元死亡,因此铁含量的增加可能是DA含量减少的原因之一,甲磺酸去铁胺具有保护DA神经元的作用。     

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。     

人参皂甙Rg1对去卵巢帕金森病模型大鼠黑质多巴胺能神经元的保护作用

目的：探讨人参皂甙Rg1对6-羟基多巴（6-OHDA）制备的去卵巢（OVX）帕金森病（PD）模型大鼠黑质（SN）多巴胺能神经元的保护作用及其可能机制。方法：应用6-OHDA制备的OVX PD模型大鼠,侧脑室给予Rg1或雌激素。免疫组织化学染色酪氨酸羟化酶（TH）阳性神经元和Bcl-2蛋白。Perls’铁染色检测SN铁含量。结果：①Rg1或雌激素可抑制阿朴吗啡诱导的PD大鼠旋转行为;②在损毁侧SN,Rg1或雌激素用药组TH阳性神经元数量较6-OHDA组显著增多;③6-OHDA组损毁侧SN内铁含量较健侧明显升高,应用Rg1或雌激素后,SN铁含量较模型组明显减少;④与6-OHDA模型组相比,Rg1及雌激素均可增加损毁侧大鼠SN内Bcl-2蛋白表达。结论：人参皂甙Rg1具有类雌激素样作用,对OVX PD模型大鼠黑质DA能神经元有明显的保护作用,其作用机制可能与降低铁负载和抗凋亡有关。     

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。     

6-OHDA制备的帕金森病大鼠黑质神经元的超微结构改变

目的观察6-羟多巴胺(6-OHDA)单侧注射制备的帕金森病(PD)大鼠多巴胺(DA)能神经元的超微结构改变。方法单侧微量注射6-OHDA制备PD大鼠模型,用免疫荧光组织化学方法观察正常侧与6-OHDA注射侧黑质酪氨酸羟化酶(TH)阳性神经细胞及神经纤维的变化;并利用免疫电镜技术观察大鼠正常侧与注射侧黑质致密部DA能神经元的超微结构。结果免疫荧光法显示注射侧黑质致密部TH阳性细胞数和网状部TH阳性纤维面积与正常侧的百分比平均值分别为21.83%,23.19%。免疫电镜显示:TH免疫反应阳性产物表达于PD大鼠正常侧DA能神经元的高尔基复合体质膜面及胞质内,电子密度较高,注射侧很少见或几乎未见,且注射侧线粒体嵴有不同程度的溶解,呈空泡样变或髓样变,粗面内质网脱颗粒。结论6-OHDA可引起DA能神经元发生凋亡的超微结构改变。     

6-羟基多巴胺损毁大鼠内侧前脑束早期黑质-纹状体系统的铁水平与多巴胺能神经元退变的关系

应用快速周期伏安法(fast cyclic vohammetry,FCV)、原子吸收分光光度法及免疫组织化学方法,观察了6-羟基多巴胺(6-hydroxydopamine,6-OHDA)单侧损毁大鼠内侧前脑束(medial forebrain bundle,MFB)早期黑质(sub-stantia nigra,sN)铁水平与多巴胺(dopamine,DA)神经元损伤的变化,以及纹状体(striatum,Str)的DA释放。结果如下：6-OHDA单侧损毁大鼠MFB1d和3d后,SN的酪氨酸羟化酶(tyrosine hydroxylase,TH)阳性细胞分别下降了45％和66％;与正常鼠和未损毁侧相比,损毁侧SN的铁染色增强,铁浓度增加,而Str的DA释放量不变;6-OHDA损毁后1d与3d组相比,损毁侧的铁染色、铁浓度及DA释放量差别无显著性。上述结果表明,6-OHDA单侧损毁大鼠MFB的早期阶段,SN的DA能神经元数目中等程度减少时,铁染色及铁浓度即有增加,由于DA能神经系统有强大的代偿功能,使得Str的DA释放量仍趋于正常。     

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。     

帕金森病模型大鼠行为学改变与黒质致密部多巴胺能神经元存活率之间的相关性

目的探讨线刀损毁内侧前脑束建立的帕金森病模型大鼠行为学改变与黒质致密部多巴胺能神经元存活率之间的相关性。方法采用可伸缩线刀切断大鼠内侧前脑束建立单侧损伤的帕金森病大鼠模型;皮下注射阿朴吗啡后测试大鼠的旋转行为;取中脑黑质切片进行酪氨酸羟化酶免疫组织化学染色,通过计数黑质致密部酪氨酸羟化酶阳性神经元的数目得到多巴胺能神经元存活率。结果模型组大鼠损伤侧酪氨酸羟化酶阳性神经元的数目明显下降,而由阿朴吗啡诱导的旋转行为明显增加。结论线刀损毁术后4周,帕金森病模型大鼠由阿朴吗啡诱导的旋转行为和黒质致密部多巴胺能神经元存活率之间存在着明显的负相关。     

蝎毒耐热肽对6羟多巴早期帕金森病大鼠的神经保护作用（英文）

本文旨在研究蝎毒耐热肽(SVHRP)是否可以缓解早期帕金森病(Parkinson’s disease,PD)模型中脑神经元线粒体超微结构异常和氧化应激。将6羟多巴(6-OHDA,20μg/3μL含0.1%抗坏血酸生理盐水)单侧注射到Sprague Dawley(SD)大鼠纹状体制备早期PD模型,PD大鼠腹腔注射SVHRP或相同体积对照溶液(生理盐水)处理1周。在6-OHDA注射2周后,对大鼠进行行为学检测;6-OHDA注射3周后,用免疫组织化学法检测多巴胺能神经元的免疫反应活性,用电子显微镜观察中脑神经元线粒体的超微结构,用试剂盒检测中脑神经元线粒体的单胺氧化酶B活性、超氧化物歧化酶活性和丙二醛含量,并进一步检测血清抑制羟自由基能力和抗氧化能力。结果显示,早期PD大鼠多巴胺能神经元的光密度相对对照组明显降低,中脑神经元线粒体超微结构的损伤显著加重,超氧化物歧化酶活性明显下降,单胺氧化酶B活性和丙二醛含量显著升高,血清抑制羟自由基能力和总的抗氧化能力显著下降。而SVHRP能够明显逆转6-OHDA的上述损伤作用。以上结果提示,SVHRP通过减轻早期PD的异常氧化应激和超微结构的损伤来发挥神经保护作用。     

Contralateral Retinal Dopamine Decrease and Melatonin Increase in Progression of Hemiparkinsonium Rat

Both dopamine (DA) and melatonin (MLT) are abundant neuromodulators located in vertebrate retina. The retinal DA deficiency and variations in MLT levels have been linked to Parkinson’s disease (PD). No studies have investigated the ipsilateral and contralateral DA and MLT in retina and their relationships in 6-hydroxydopamine (6-OHDA) induced hemiparkinsonian rats. We established PD rat model by unilateral injection of 6-OHDA into the right substantia nigra and the right medial forebrain bundle. Eye tissue was collected and the levels of MLT and DA were measured twice daily at 10:00 and 22:00. The concentrations of DA and its metabolites, 3,4-dihydroxyphenylacetic (DOPAC) and homovanillic acid (HVA), as well as MLT were determined by HPLC. The results show that DA levels in the eye contralateral to the side of a unilateral intracerebral 6-OHDA lesion significantly decreased (P < 0.001). Both the ratios of DOPAC/DA and HVA/DA were increased in comparison with the vehicle groups after 3 weeks post-lesion. The concentrations of MLT at 10:00 and 22:00 in both eyes were distinctly increased compared with the vehicle groups (P < 0.05). The change of DA and its metabolites, as well as MLT appeared to correlate well with the rotation behavior of rats. These findings suggest that rats receive a unilateral intracerebral injection of 6-OHDA that mainly causes the contralateral eye destruction of DA-containing neurons. Increased retinal MLT level probably is associated with the progression of PD.     

Increased melatonin may play dual roles in the striata of a 6-hydroxydopamine model of Parkinson's disease

AimsTo investigate dynamic changes and roles of melatonin (MLT) in the striata of 6-hydroxydopamine (6-OHDA)-treated rats.Main methodsA Parkinson's disease (PD) rat was established by a unilateral injection of 6-OHDA into the right substantia nigra pars compacta (SNc) and the right medial forebrain bundle (MFB) to achieve a complete lesion of the ipsilateral nigrostriatal DA system. Dialysates were collected in the lesioned striatum at different time intervals by in vivo microdialysis. In addition, both contralateral and ipsilateral striatum tissues were collected at two time intervals (10:00 and 22:00 h) at 3 and 6 weeks after lesioning. The levels of DA, 3, 4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in the dialysates, as well as MLT in the dialysates and tissues were determined using HPLC.Key findingsThe dialysate contents of DA, DOPAC and HVA in the lesioned striatum were significantly decreased (P < 0.001) in comparison with those in the controls or in the unlesioned side 3 weeks after lesioning while the extracellular level of MLT in the lesioned striatum in these corresponding time intervals distinctly increased when compared with those in the controls (P < 0.05). The tissue MLT contents increased in the bilateral striata in different degrees at 6 weeks post-lesion (P < 0.05). Moreover, increased MLT levels correlate well with rotations or DA changes in the lesioned striatum.SignificanceThese data suggest that 6-OHDA lesion manipulates the MLT secretion pattern. Increased striatal MLT level by a unilateral intracerebral injection of 6-OHDA may play dual roles in the progression of PD in rats.     

Role of nitric oxide in a progressive neurodegeneration model of Parkinson's disease in the rat

Abstract

This study was undertaken to investigate the nitric oxide synthase (NOS) activity in the striatum following 6-hydroxydopamine (6-OHDA) induced neurodegeneration in rats. Constitutive NOS (cNOS) activity remained unaltered at 3, 7 and 14 days after lesion, while a 43% and 45% decrease was observed at 30 and 50 days, respectively. Inducible NOS (iNOS) activity was detected only on the 3rd day after lesion and not in subsequent days or the control striatum. N^G-nitro-L-arginine methyl ester (L-NAME) pretreatment blocked the amphetamine-induced rotations and inhibited the iNOS activity at the 3rd day after the 6-OHDA injection. L-NAME pretreatment also significantly restored the striatal dopamine (DA), dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) levels in 6-OHDA treated rats. Thus a possible role of nitric oxide in 6-OHDA induced neurodegeneration is suggested.     

Efficacy of Brain-Derived Neurotrophic Factor and Neurotrophin-3 on Neurochemical and Behavioral Deficits Associated with Partial Nigrostriatal Dopamine Lesions

Abstract: Brain-derived neurotrophic factor (BDNF) promotes the survival of dopamine (DA) neurons, enhances expression of DA neuron characteristics, and protects these cells from 6-hydroxydopamine (6-OHDA) toxicity in vitro. We tested the ability of BDNF or neurotrophin-3 (NT-3) to exert similar protective effects in vivo during chronic delivery of 6-OHDA to the rat neostriatum. Chronic infusions of BDNF or NT-3 (12 µg/day) above the substantia nigra were started 6 days before and continued during an 8-day chronic intrastriatal infusion of 6-OHDA. In control and neurotrophin-treated animals, 6-OHDA treatment selectively depleted 50–60% of nigrostriatal DA nerve terminals but produced little if any loss of pars compacta DA cell bodies. This partial DA lesion resulted in three rotations per minute toward the lesioned hemisphere after treatment with the DA release-inducing drug d-amphetamine. Compared with supranigral infusions of vehicle, BDNF and NT-3 decreased the number of these ipsiversive rotations by 70 and 48% and increased by 20- and 10-fold, respectively, the number of contraversive rotations observed after amphetamine injection. When challenged with the DA receptor agonist apomorphine, BDNF- and NT-3-treated animals also exhibited a seven- and 3.5-fold increase in the number of contraversive rotations relative to the vehicle group, respectively. Compared with vehicle, BDNF increased striatal levels of homovanillic acid (HVA; 86%), 3,4-dihydroxyphenylacetic acid (DOPAC; 42%), and 5-hydroxyindoleacetic acid (5-HIAA; 32%) and the HVA/DA (43%) and 5-HIAA/serotonin (34%) ratios in the DA-denervated striatum. NT-3 augmented only striatal 5-HIAA levels (24%). Neither factor altered the 6-OHDA-induced decrease in striatal DA levels or high-affinity DA uptake and thus did not protect against the destruction of DA terminals and did not alter striatal D₁ or D₂ ligand binding. Choline, GABA, and glutamate uptake in the striatum were not altered by the lesion or neurotrophin treatment. Thus, BDNF and to a lesser extent NT-3 reverse rotational behavioral deficits and augment striatal DA and 5-HT metabolism in a partial DA lesion model.     

Protective effects of N-acetylserotonin against 6-hydroxydopamine-induced neurotoxicity

The present work studied in vivo neuroprotective effects of n-acetylserotonin (NAS), the immediate precursor of melatonin, on the dopaminergic system, in rats lesioned with the unilateral intrastriatal injection of the neurotoxin 6-hydroxydopamine (6-OHDA). Two weeks after the lesion, the dopamine receptor agonist, apomorphine, produced rotational asymmetry, and the NAS treatment significantly reduced the motor deficit following the apomorphine challenge. The apomorphine-induced rotational behavior was blocked by 84, 86 and 53% after NAS, at doses of 2, 5 and 10 mg/kg, i.p., respectively. The injection of 6-OHDA significantly decreased DA, DOPAC and HVA levels in the rat striatum. In contrast, the NAS (2, 5 and 10 mg/kg, i.p., daily for 7 days) treatment partially reversed the decreases caused by 6-OHDA, and the neurotransmitter levels were brought to approximately 50% of that observed in the contralateral sides. NAS was more efficient at the smaller doses. NAS (5 mg/kg) produced an up-regulation of D1 (37%) and D2 (37%) receptors associated with a decrease in Kd values.     

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。     

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.     

Dopamine Metabolites in Rat Cisternal Cerebrospinal Fluid: Major Contribution from Extrastriatal Dopamine Neurones

The interpretation of central 3,4-dihydroxyphenylethylamine (dopamine, DA) metabolism, as indicated by determinations in rat cisternal CSF, was investigated using intrastriatal injection of the DA neurotoxin 6-hydroxydopamine (6-OHDA) and intraperitoneal injection of the noradrenergic neurotoxin N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP4). DA turnover was subsequently determined by measurement of the rate of accumulation of total 3,4-dihydroxyphenylacetic acid and homovanillic acid (DOPAC + HVA) in the CSF after probenecid was given. Two days later the rats were killed, and metabolism of DA and 5-hydroxytryptamine (5-HT) was investigated by determining levels of the amines and their metabolites in brain regions. Although 6-OHDA greatly decreased striatal DA metabolism, this was not paralleled by DA turnover as indicated by CSF, as this fell only moderately and approximately in parallel with results for the brain as a whole. 5-HT metabolism was essentially unaltered. DSP4 considerably depleted noradrenaline and caused smaller decreases of 5-HT metabolism in some regions. However, DA metabolism was not significantly affected, either in brain or CSF, which suggests that noradrenaline neurones make only a small contribution to central DA metabolism. Results as a whole suggest that DOPAC and HVA concentrations in rat cisternal CSF reflect whole brain DA metabolism and derive predominantly from DA neurones in extrastriatal regions of the brain.     

Neurotoxic action of 6-hydroxydopamine on the nigrostriatal dopaminergic pathway in rats sensitized with D-amphetamine.

To determine whether behavioral sensitization produced by prolonged D-amphetamine administration affects susceptibility of nigrostriatal dopaminergic neurons to the neurotoxic actions of 6-hydroxydopamine (6-OHDA), rats were treated daily from the 23 rd day after birth for 11 consecutive days with D-amphetamine (1.0 mg/kg s.c.) or saline. On the last day of treatment, one group primed with D-amphetamine and one control group of rats were tested to confirm behavioral sensitization development. The remaining animals were additionally treated on the 34 th day (one day after the last D-amphetamine injection) with 6-OHDA HBr (300 microg in 10 microl i.c.v., salt form, half in each lateral ventricle) or its vehicle. Four weeks later the levels of dopamine (DA) and its metabolites 3,4-dihydroxyphenylacetic acid (DOPAC), homovanillic acid (HVA), 3-metoxytyramine (3-MT), as well as 5-hydroxytrypatmine (5-HT) and its metabolite 5-hydroxyindoleacteic acid (5-HIAA) were assayed in the striatum, by HPLC/ED. In rats with behavioral sensitization, 6-OHDA reduced endogenous dopamine and its metabolites content to a comparable degree in comparison to controls. This finding indicates that presumed up-regulation of the dopamine transporter in the behaviorially sensitized rats did not increase the neurotoxicity of a high dose of 6-OHDA.     

Evaluation of Estrogen Neuroprotective Effect on Nigrostriatal Dopaminergic Neurons Following 6-Hydroxydopamine Injection into the Substantia Nigra Pars Compacta or the Medial Forebrain Bundle

Studies involving estrogen treatment of ovariectomized rats or mice have attributed to this hormone a neuroprotective effect on the substantia nigra pars compacta (SNpc) neurons. We investigated the effect of estradiol replacement in ovariectomized rats on the survival of dopaminergic mesencephalic cell and the integrity of their projections to the striatum after microinjections of 1 microg of 6-hydroxydopamine (6-OHDA) into the right SNpc or medial forebrain bundle (MFB). Estradiol replacement did not prevent the reduction either in the striatal concentrations of DA and metabolites or in the number of nigrostriatal dopaminergic neurons following lesion with 1 microg of 6-OHDA into the SNpc. Nevertheless, estradiol treatment reduced the decrease in striatal DA following injection of 1 microg of 6-OHDA into the MFB. Results suggest therefore that estrogen protect nigrostriatal dopaminergic neurons against a 6-OHDA injury to the MFB but not the SNpc. This may be due to the distinct degree of lesions promoted in these different rat models of Parkinson's disease.