Neuroprotective and neurorescue effect of black tea extract in 6-hydroxydopamine-lesioned rat model of Parkinson's disease

In the present study, an attempt has been made to explore the neuroprotective and neuroreparative (neurorescue) effect of black tea extract (BTE) in 6-hydroxydopamine (6-OHDA)-lesioned rat model of Parkinson's disease (PD). In the neuroprotective (BTE + 6-OHDA) and neurorescue (6-OHDA + BTE) experiments, the rats were given 1.5% BTE orally prior to and after intrastriatal 6-OHDA lesion respectively. A significant recovery in d-amphetamine induced circling behavior (stereotypy), spontaneous locomotor activity, dopamine (DA)-D2 receptor binding, striatal DA and 3-4 dihydroxy phenyl acetic acid (DOPAC) level, nigral glutathione level, lipid peroxidation, striatal superoxide dismutase and catalase activity, antiapoptotic and proapoptotic protein level was evident in BTE + 6-OHDA and 6-OHDA + BTE groups, as compared to lesioned animals. BTE treatment, either before or after 6-OHDA administration protected the dopaminergic neurons, as evident by significantly higher number of surviving tyrosine hydroxylase immunoreactive (TH-ir) neurons, increased TH protein level and TH mRNA expression in substantia nigra. However, the degree of improvement in motor and neurochemical deficits was more prominent in rats receiving BTE before 6-OHDA. Results suggest that BTE exerts both neuroprotective and neurorescue effects against 6-OHDA-induced degeneration of the nigrostriatal dopaminergic system, suggesting that possibly daily intake of BTE may slow down the PD progression as well as delay the onset of neurodegenerative processes in PD.     

A potential target for the treatment of Parkinson's disease: Effect of lateral habenula lesions

ObjectiveParkinson's disease (PD) is a progressive neurodegenerative movement disorder that is caused predominantly by the degeneration of the nigrostriatal dopaminergic pathway. Lateral habenula (LHb) has efferent projections that terminate in the substantia nigra pars compacta (SNpc) and electrical stimulation of the LHb effectively suppresses the activity of dopamine-containing neurons in the SNpc. This study was aimed to investigate whether LHb lesions can ameliorate the syndromes of PD via affecting the activities of SNpc neurons in 6-hydroxydopamine (6-OHDA)-induced PD model rats.MethodsConcentrations of dopamine (DA) and its metabolites dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in the striatum, which is the area projected by the SNpc dopaminergic neurons were assayed by high-performance liquid chromatography (HPLC) coupled with fluorescence detection. The immunohistochemical method was applied to detect the numbers of tyrosine hydroxylase (TH)-positive cells in the substantia nigra.ResultsThe results showed that LHb lesions induced a significant reduction in apomorphine-induced rotational behavior. The DA, DOPAC and HVA levels in the striatum of PD model rats were increased by the LHb lesions.ConclusionTherefore, we speculate that the LHb lesions induced a significant amelioration in motor disorders via increasing the DA levels in the striatum, which may lead to a potential therapeutic strategy for the treatment of PD.     

偏侧帕金森病大鼠模型的行为,免疫组化和脑微透析的实验研究

评价6-羟多巴胺(6-OHDA)损毁大鼠单侧黑质制备的偏侧帕金森病动物模型。应用6-羟多巴胺损毁SD大鼠单侧黑质制备偏侧PD鼠模型。3周后根据药物诱发试验,TH免疫组化证实模型制作成功。进一步用脑微透析技术结合HPLC-ECD在体检测PD鼠纹状体多巴胺及代谢产物含量。结果:82只大鼠中有36只阿朴吗啡(APO)诱发的旋转次数>7转/min。6-OHDA注射侧黑质DA神经末稍已绝大多数被损毁。6-OHDA损毁侧纹状体多巴胺及代谢产物明显低于健侧(P<0.05,P<0.01)。应用6-OHDA制备的偏侧PD鼠模型是PD研究的理想模型之一。     

Long-term survival of grafted cells, dopamine synthesis/release, synaptic connections, and functional recovery after transplantation of fetal nigral cells in rats with unilateral 6-OHDA lesions in the nigrostriatal dopamine pathway

In animal models of hemi-Parkinson's disease, survival of grafted nigral cells, their synaptic connections, dopamine (DA) synthesis/release, and recovery from motor disturbances were investigated, and these were compared among 3 groups of animals raised for 3 months, 1 year and 2 years after the transplantation. Fetal nigral DAergic cell suspensions were transplanted in the ipsilateral caudate nucleus of rats with unilateral 6-OHDA lesions in the nigrostriatal DA pathway. Motor disturbances, assessed by methamphetamine-induced rotation, recovered partly in the 2nd week, significantly in the 4th week after the grafting, and remained stable thereafter. Many tyrosine hydroxylase (TH)-positive cells were detected along the grafting tracks. The number of TH-positive cells was similar in the 3 groups of animals. These TH-positive cells made synaptic connections in the host caudate. By in vivo microdialysis measurement, extracellular DA, dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) around the grafted sites recovered to 30-100% of those of controls. No significant differences were observed in the concentration of DA, DOPAC and HVA among 3 groups of animals. They also responded to methamphetamine loading though the magnitudes were smaller. Using a TH cDNA probe, TH-positive cells were found to express TH mRNA in in situ hybridization-autoradiographic analysis. Data indicate that grafted fetal DAergic cells survive, synthesize and release DA, make synaptic connections in the host brain and ameliorate motor disturbances for over 2 years. There were no differences in these parameters among the 3 groups of animals, and no untoward side effects were observed even at 2 years after the grafting. Thus it was confirmed that the grafting of neuronal cells into the brain is a promising approach to restore disturbed function.     

An experimental study on intracerebroventricular transplantation of human amniotic epithelial cells in a rat model of Parkinson's disease

Abstract

Objectives: Human amniotic epithelial (HAE) cells are formed from amnioblasts, separated from the epiblast at about the eighth day after fertilization. In the present study, we attempt to investigate the effects of intracerebroventricular transplantation of HAE cells on Parkinson's disease (PD) rats.

Methods: A PD rat model was induced by 6-OHDA injections. Then the rats were transplanted intracerebroventricularly with HAE cells. Apomorphin-induced turns were used to assess the neurobehavioral deficit in rats. Immunofluorescence cytochemistry was used to track the survival of HAE cells. Tyrosinehydroxylase (TH) immunohistochemistry was used to determine the density of TH-positive cells in rat substantia nigra and the differentiation of HAE cells. High performance liquid chromatography (HPLC) was used to measure the levels of dopamine (DA) and its metabolites 3, 4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in rat striatum. HVA levels in the cerebrospinal fluid of rats were also determined by HPLC.

Results: The results showed that transplanted HAE cells can survive for at least 10 weeks and differentiate into TH-positive cells in PD rats. The grafts significantly ameliorated apomorphine-induced turns in PD rats. TH immunohistochemistry showed that HAE cells attenuated the loss of TH-positive cells in rat substantia nigra. In addition, HAE cells prevented the fall of DA and its metabolites DOPAC and HVA in PD rats. Increased HVA levels in the cerebrospinal fluid of PD rats were also observed.

Conclusion: These results demonstrate that HAE cells have beneficial effect on 6-OHDA-induced PD rats, which may be due to the neurotrophic factors secrete by HAE cells.     

人羊膜上皮细胞移植治疗帕金森病鼠的研究

目的 观察人羊膜上皮细胞在帕金森病鼠移植后的存活情况,以及它对帕金森病鼠旋转行为的改善作用.方法 采用6-羟多巴胺立体定向纹状体注射制作帕金森病鼠模型;51只大鼠随机分三组:人羊膜上皮细胞移植组、假手术PBS对照组以及空白模型对照组.制模成功后第5周用人特异性抗体Nestin和Vimentin检测人羊膜细胞的存活情况,第10周切片观察黑质部TH阳性神经元的变化情况,高效液相色谱--电化学仪测定纹状体多巴胺(DA),高香草酸(HVA),3,4-二羟基苯乙酸(DOPAC)等浓度以及脑脊液DA的含量.结果 人羊膜上皮细胞帕金森病鼠侧脑室内移植可以存活达10周;移植组大鼠旋转数较对照组明显降低(P≤0.01);黑质部TH阳性神经元数量较对照组升高(P≤0.01),纹状体区DA、HVA和DOPAC含量较PBS对照组明显升高(P＜0.01～0.05),移植组脑脊液DA含量较PBS对照组也显著增加(P＜0.01).结论 人羊膜上皮细胞侧脑室移植可以改善帕金森病鼠的旋转行为,其机制可能与其增加纹状体区多巴胺等递质水平有关.     

Dopamine differentiation factors increase striatal dopaminergic function in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-lesioned mice

We have previously shown that muscle-derived differentiation factors (MDF) and human recombinant acidic fibroblast growth factor (aFGF) have beneficial behavioral and neurochemical effects on the nigrostriatal dopaminergic neurons of 6-hydroxy-dopamine (6-OHDA)-lesioned rats (Jin and Iacovitti: Neurobiol Dis 2:1–12, 1995). In the present study, we determined the effects of similar treatments on mice treated with the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Five days after unilateral striatal infusion of MDF or aFGF into MPTP-lesioned mice, striatal tyrosine hydroxylase (TH) activity and dihydroxyphenylacetic acid (DOPAC) levels were bilaterally increased (20–35%) compared to untreated (lesion only) or control (phosphate buffered saline + bovine serum albumin) mice. These increases, however, were not accompanied by change in dopamine (DA) levels, indicating an elevation of DA synthesis (TH/DA) and turnover (DOPAC/DA). The present findings that MDF and aFGF may have neurochemical effects in vivo on the lesioned nigrostriatal dopaminergic system suggest their potential pharmacological role in the treatment of Parkinson's disease. © 1996 Wiley-Liss, Inc.     

Estrogen interacts with the IGF-1 system to protect nigrostriatal dopamine and maintain motoric behavior after 6-hydroxdopamine lesions

The most prominent neurochemical hallmark of Parkinson's disease (PD) is the loss of nigrostriatal dopamine (DA). Animal models of PD have concentrated on depleting DA and therapies have focused on maintaining or restoring DA. Within this context estrogen protects against 6-hydroxdopamine (6-OHDA) and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) lesions of the nigrostriatal DA pathway. Present studies tested the hypothesis that neuroprotective estrogen actions involve activation of the insulin-like growth factor-1 (IGF-1) system. Ovariectomized rats were treated with either a single subcutaneous injection of 17beta-estradiol benzoate or centrally or peripherally IGF-1. All rats were infused unilaterally with 6-OHDA into the medial forebrain bundle (MFB) to lesion the nigrostriatal DA pathway. Tyrosine hydroxylase (TH) immunocytochemistry confirmed that rats injected with 6-OHDA had a massive loss of TH immunoreactivity in both the ipsilateral substantia nigra compacta (60% loss) and the striatum (>95% loss) compared to the contralateral side. Loss of TH immunoreactivity was correlated with loss of asymmetric forelimb movements, a behavioral assay for motor deficits. Pretreatment with estrogen or IGF-1 significantly prevented 6-OHDA-induced loss of substantia nigra compacta neurons (20% loss) and TH immunoreactivity in DA fibers in the striatum (<20% loss) and prevented the loss of asymmetric forelimb use. Blockage of IGF-1 receptors by intracerebroventricular JB-1, an IGF-1 receptor antagonist, attenuated both estrogen and IGF-1 neuroprotection of nigrostriatal DA neurons and motor behavior. These findings suggest that IGF-1 and estrogen acting through the IGF-1 system may be critical for neuroprotective effects of estrogen on nigrostriatal DA neurons in this model of PD.     

沉默信息调节因子1/p53信号通路参与MPTP诱导的帕金森病小鼠多巴胺能神经元丢失

目的研究沉默信息调节因子1(SIRT1)和p53在MPTP诱导的帕金森病(PD)小鼠模型多巴胺能神经元凋亡中的可能作用。方法将健康雄性C57BL/6小鼠随机分为对照组、MPTP组,采用行为学方法检测行为学改变,高效液相色谱(HPLC)检测多巴胺(DA)、二羟基苯乙酸(DOPAC)和高香草酸(HVA)的含量变化,免疫荧光染色法观察两组小鼠黑质酪氨酸羟化酶(TH)阳性神经元数目的变化及SIRT1表达情况,TUNEL法观察黑质细胞凋亡情况,Western blot法检测TH、SIRT1、p53、乙酰化p53 (ac-p53)、B淋巴细胞瘤-2基因(Bcl-2)和Bax的表达情况。结果行为学结果显示MPTP组小鼠爬杆转向时间及爬杆总时间均较对照组小鼠显著延长(P 0. 01)。HPLC结果提示MPTP组的DA、DOPAC及HVA含量较对照组显著下降(P 0. 01)。免疫荧光结果显示MPTP小鼠黑质区TH阳性神经元数目及SIRT1表达较对照组均显著减少。TUNEL检测结果显示,与对照组相比,MPTP组凋亡阳性细胞数明显增多。Western blot结果显示,与对照组相比,MPTP组的TH、SIRT1、Bcl-2蛋白表达显著下降(P 0. 01),p53、ac-p53、Bax蛋白表达显著升高(P 0. 01)。结论MPTP模型小鼠行为学异常、TH阳性神经元减少、DA及其代谢产物下降提示成功复制PD动物模型,同时MPTP模型小鼠的SIRT1、p53及凋亡相关蛋白表达异常,提示该信号通路可能参与了PD的疾病过程。     

Neurotrophic effects of bone morphogenetic protein-7 in a rat model of Parkinson's disease

Previous studies have demonstrated that pretreatment with bone morphogenetic protein-7 (BMP7) reduces ischemic neuronal injury in vivo. Moreover, exogenous application of BMP7 increases both the number of tyrosine hydroxylase (+) cells and dopamine (DA) uptake in rat mesencephalic cell cultures. The purpose of this study was to investigate the in vivo effects of BMP7 on 6-hydroxydopamine (6-OHDA) induced lesioning of midbrain DA neurons. Adult Fischer 344 rats were anesthetized and injected with BMP7 or vehicle into the left substantia nigra, followed by local administration of 9 microg of 6-OHDA into the left medial forebrain bundle. The lesioned animals that received BMP7 pretreatment, as compared to vehicle/6-OHDA controls, had a significant reduction in methamphetamine-induced rotation 1 month after the surgery. BMP7-pretreatment partially preserved KCl-induced dopamine release in the lesioned striatum and significantly increased TH immunoreactivity in the lesioned nigra and striatum. In summary, our data suggest that BMP7 has neuroprotective and/or neuroreparative effects against 6-OHDA lesioning of the nigrostriatal DA pathway in an animal model of Parkinson's disease (PD).     

Effect of Adenosine A2A Receptor Antagonists and l-DOPA on Hydroxyl Radical, Glutamate and Dopamine in the Striatum of 6-OHDA-Treated Rats

A(2A) adenosine receptor antagonists have been proposed as a new therapy of PD. Since oxidative stress plays an important role in the pathogenesis of PD, we studied the effect of the selective A(2A) adenosine receptor antagonists 8-(-3-chlorostyryl)caffeine (CSC) and 4-(2-[7-amino-2-(2-furyl)[1,2,4]triazolo[2,3-a][1,3,5]triazin-5-ylamino]ethyl)phenol (ZM 241385) on hydroxyl radical generation, and glutamate (GLU) and dopamine (DA) extracellular level using a microdialysis in the striatum of 6-OHDA-treated rats. CSC (1 mg/kg) and ZM 241385 (3 mg/kg) given repeatedly for 14 days decreased the production of hydroxyl radical and extracellular GLU level, both enhanced by prior 6-OHDA treatment in dialysates from the rat striatum. CSC and ZM 241385 did not affect DA and its metabolites, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanilic acid (HVA) extracellular levels in the striatum of 6-OHDA-treated rats. L-DOPA (6 mg/kg) given twice daily for two weeks in the presence of benserazide (3 mg/kg) decreased striatal hydroxyl radical and glutamate extracellular level in 6-OHDA-treated rats. At the same time, L-DOPA slightly but significantly increased the extracellular levels of DOPAC and HVA. A combined repeated administration of L-DOPA and CSC or ZM 241385 did not change the effect of L-DOPA on hydroxyl radical production and glutamate extracellular level in spite of an enhancement of extracellular DA level by CSC and elevation of extracellular level of DOPAC and HVA by ZM 241385. The data suggest that the 6-OHDA-induced damage of nigrostriatal DA-terminals is related to oxidative stress and excessive release of glutamate. Administration of L-DOPA in combination with CSC or ZM 241385, by restoring striatal DA-glutamate balance, suppressed 6-OHDA-induced overproduction of hydroxyl radical.     

Relationships between various behavioural abnormalities and nigrostriatal dopamine depletion in the unilateral 6-OHDA-lesioned rat

While rotational asymmetry is used as a characteristic behavioural sign of striatal dopamine (DA) loss in unilateral animal models of Parkinson's disease (PD), there is relatively little analysis of how other common behavioural deficits relate to nigrostriatal DA depletion. We analysed the relationships between several deficits induced by unilateral 6-OHDA lesions and striatal neurochemistry, as well as neuronal loss in the dopaminergic substantia nigra (SN). Behaviour was evaluated from before until 6 weeks after surgery and abnormalities appeared in body axis, head position and sensorimotor performance as well as apomorphine-induced rotation. As expected, rotational behaviour correlated with striatal DA loss and not with other striatal neurotransmitters measured. Similar observations were found for sensorimotor deficits ('disengage task'). Both deficits were observed in rats with >70% loss of TH+ nigral neurons and >80% loss of striatal DA. Additional postural abnormalities appeared with mean losses of 87% of nigral DA neurons and 97% striatal DA, consistent with observations in patients with advanced PD. The data show that the repertoire of behavioural abnormalities manifested by hemiparkinsonian rats relate directly to the degree of nigrostriatal DA loss and, therefore, mimic features of PD. Analysis of such behaviours are relevant for chronic therapeutic studies targeting PD.     

Differential activation of PKC delta in the substantia nigra of rats following striatal or nigral 6-hydroxydopamine lesions

Parkinsonian neurodegeneration is associated with heightened levels of oxidative stress and the activation of apoptotic pathways. In an in vitro cellular model, we reported that 6-hydroxydopamine (6-OHDA) induces apoptotic cell death via the induction of mitochondrial dysfunction, the activation of caspase 3 and the consequent proteolytic activation of the redox-sensitive kinase, protein kinase C (PKC)δ, in PC12 cells. Here we have investigated the involvement of PKCδ in 6-OHDA-induced cell death in vivo . The nigrostriatal pathway of rats was lesioned by unilateral infusion of 6-OHDA into either the striatum or substantia nigra pars compacta (SNpc). Infusion into the SNpc resulted in rapid loss of tyrosine hydroxylase (TH)-positive cells (87% decrease after 4 days), consistent with a necrotic-like mode of cell death. In contrast, striatal infusion initiated a slower, progressive decline in TH immunoreactivity (25% decrease in the SNpc after 4 days); cell appearance was characteristic of apoptosis. This is consistent with a transient increase in active caspase 3 immunoreactivity at 4 days post-infusion, and a concomitant proteolytic activation of PKCδ in the SNpc of striatal-lesioned rats. Cleavage of PKCδ did not occur in the striatum or cerebellum of lesioned animals, or in the SNpc of sham-operated controls. No increase in caspase 3 immunoreactivity or proteolytic activation of PKCδ was detected in nigral-lesioned rats. These results suggest that after 6-OHDA infusion into the striatum, retrograde neurotoxicity induces caspase 3-dependent PKCδ proteolytic activation in the cell bodies of the SNpc, implicating this kinase in the neurodegenerative process.     

In vivo measurement of spontaneous release and metabolism of dopamine from intrastriatal nigral grafts using intracerebral dialysis

Spontaneous release and metabolism of dopamine (DA) from intrastriatal grafts of fetal mesencephalic DA neurons was measured by intracerebral dialysis. Mesencephalic DA cell suspensions were implanted into the head of the caudate-putamen in rats with unilateral 6-hydroxydopamine (6-OHDA) lesions of the mesostriatal DA pathway. Four months later, when tests for amphetamine-induced turning behaviour showed that the grafts had become functional, loops of dialysis tubing were implanted into the striatum on the grafted side and the contralateral non-lesioned side of the grafted rats, and in a similar position in the denervated caudate-putamen of 6-OHDA lesioned control rats. Dialysis perfusates collected from the 6-OHDA lesioned striata showed a reduction of about 95-98% in DA and its metabolites 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA). In the grafted animals these levels had recovered to about 40% of control for DA and to 12-16% of control for HVA and DOPAC. In addition, the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) was increased in the grafted striata compared to both the lesioned and non-lesioned controls. Amphetamine had little or no effect on DA release in the 6-OHDA lesioned rats, but caused a marked increase in DA release in the grafted rats, this response being proportional to that seen in intact striata. Since the subsequent histochemical analysis showed that the dialysis probe had been located in the transplant-reinnervated part of the caudate-putamen, the results provide additional evidence that the grafted DA neurons exert their functional effects through a continuous active transmitter release from their newly-established terminals in the reinnervated host target.     

Depressive-like behaviors alterations induced by intranigral MPTP, 6-OHDA,LPS and rotenone models of Parkinson's disease are predominantly associated with serotonin and dopamine

Depression is a frequently encountered non-motor feature of Parkinson's disease (PD) and it can have a significant impact on patient's quality of life. Considering the differential pathophysiology of depression in PD, it prompts the idea that a degenerated nigrostriatal system plays a role in depressive-like behaviors, whilst animal models of PD are employed. Therefore, we addressed the question of whether dopamine (DA) depletion, promoted by the neurotoxins 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), 6-hydroxydopamine (6-OHDA), lipopolysaccharide (LPS) and rotenone are able to induce depressive-like behaviors and neurotransmitters alterations similarly that encountered in PD. To test this rationale, we performed intranigral injections of each neurotoxin, followed by motor behavior, depressive-like behaviors, histological and neurochemical tests. After the motor recovery period, MPTP, 6-OHDA and rotenone were able to produce anhedonia and behavioral despair. These altered behavioral responses were accompanied by reductions of striatal DA, homovanillic acid (HVA) and 3,4-dihydroxyphenylacetic acid (DOPAC) restricted to the 6-OHDA group. Additionally, decreases on the hippocampal serotonin (5-HT) content were detected for the MPTP, 6-OHDA and rotenone groups. Notably, strong correlations were detected among the groups when 5-HT and DA were correlated with swimming (r = + 0.97; P = 0.001) and immobility (r = − 0.90; P = 0.012), respectively. Our data indicate that MPTP, 6-OHDA and rotenone, but not LPS were able to produce depressive-like behaviors accompanied primarily by hippocampal 5-HT reductions. Moreover, DA and 5-HT strongly correlated with “emotional” impairments suggesting an important participation of these neurotransmitters in anhedonia and behavioral despair after nigral lesions promoted by the neurotoxins.     

6-羟基多巴胺单侧纹状体注射对大鼠双侧多巴胺能神经元的影响

目的探讨帕金森病大鼠模型中6-羟基多巴胺（6-OHDA）单侧纹状体注射对双侧黑质纹状体多巴胺能神经元的影响。方法大鼠随机分成模型组和对照组，模型组自一侧纹状体注射6-OHDA，对照组注射PBS；用免疫组织化学方法分别检测大鼠双侧黑质和纹状体区酪氨酸羟化酶（TH）阳性细胞和纤维的表达；高效液相色谱检测双侧纹状体多巴胺（DA）及其代谢产物3，4-二羟基苯乙酸（DOPAC）和高香草酸（HVA）含量。结果模型组大鼠双侧（毁损侧与其对侧）黑质致密区TH阳性细胞数量均少于对照组（P〈0．01），模型组双侧纹状体区TH阳性纤维密度均低于对照组；模型组大鼠双侧纹状体区DA含量均低于对照组（P〈0．01）；双侧DOPAC和HVA含量也降低。结论6-羟多巴胺单侧纹状体注射制作的帕金森病大鼠模型的对侧黑质纹状体也有损伤。     

转基因成肌细胞脑内移植后帕金森病大鼠纹状体多巴胺含量的变化

为评价转鼠酪氨酸羟化酶（TH）基因的成肌细胞脑内移植对偏侧帕金森病（PD）大鼠模型纹状体区多巴胺及代谢产物含量的影响，应用6－羟多巴胺损毁SD大鼠单侧黑质制备偏侧帕金森病臣模型。模型稳定必个月后，移植转TH基因的成肌细胞（n＝24）或未转基国的成肌细胞（n＝10）于偏侧PD鼠损毁侧纹状体。移植治疗后6个月，用高效液相色谱电化学法（HPLC－ECD）检测偏侧PD鼠模型纹状体区多巴胺、3，4－二羟苯乙酸（DOPAC）以及高香草酸（HVA）含量。结果转TH基因成肌细胞植入组PD鼠纹状体区多巴胺及代谢产物含量明显增高（P＜0．01），其中多巴胺含量从治疗前平均39．20Pg／mg提高至治疗后的985．71Pg／mg，相当于正常侧纹状体的49．99％．对照组植入未转基因的成肌细胞后纹状体多巴胺及代谢产物含量无明显变化（P＞0．05）。可见转鼠TH基因的成肌细胞脑内移植能够部分改善偏侧PD鼠模型纹状体区多巴胺的缺乏，成肌细胞是PD基因治疗的合适靶细胞之一。     

Estrogen decreases corpus striatal neurotoxicity in response to 6-hydroxydopamine

Ovariectomized rats treated or not with an estradiol pellet were subjected to an unilateral intrastriatal infusion of 6-hydroxydopamine (6-OHDA). Various parameters of nigrostriatal dopaminergic function as derived from measurements of dopamine and dihydroxyphenylacetic acid (DOPAC) concentrations were determined from the 6-OHDA lesioned and non-lesioned sides of the corpus striatum in these animals. Dopamine concentrations within the 6-OHDA lesioned striatum of estrogen-treated rats were significantly greater than non-estrogen-treated rats. There were no differences in striatal dopamine concentrations between estrogen- versus non-estrogen-treated rats on their non-lesioned side. In contrast to that of dopamine, no differences in DOPAC concentrations between estrogen and non-estrogen-treated rats were obtained within the 6-OHDA-lesioned side. The DOPAC concentrations on the non-lesioned side of the striatum were significantly greater in the non-estrogen-treated rats. These results demonstrate that estrogen significantly diminishes the depletion of striatal dopamine resulting from the neurotoxin 6-OHDA. The data obtained from the DOPAC determinations imply that this capacity of estrogen may be exerted through actions upon uptake processes of striatal dopaminergic neurons. Such findings suggest that estrogen may function as an important modulatory factor capable of attenuating degeneration within the corpus striatum, and in this way serve as a neuroprotectant of the nigrostriatal dopaminergic system.     

Dose related effects of 6-OHDA on rabbit retinal dopamine concentrations and ERG B-wave amplitudes

The purpose of this study was to examine the dose related effects of 6-hydroxydopamine (6-OHDA) on the electroretinographic (ERG) B-wave amplitude and on retinal concentrations of dopamine (DA) and its main metabolites homovanillic acid (HVA) and dihydroxyphenylacetic acid (DOPAC). Doses of 6-OHDA (60, 300 or 1200 micrograms) were dissolved in a 0.9 percent NaCl and ascorbic acid solution and administered intravitreally in 300 microliter volume in one eye of adult pigmented rabbits. The fellow eye received a similar volume of the drug vehicle. With the smallest dose of 6-OHDA (60 micrograms) no changes in ERG B-wave amplitude or retinal concentrations of DA, DOPAC or HVA were found. With the largest dose of 6-OHDA (1200 micrograms) complete extinction of the ERG and almost total disappearance of DA, DOPAC and HVA were observed. With the intermediate dose of 300 micrograms 6-OHDA significant increases in B-wave amplitudes and decreases in retinal DA, DOPAC and HVA concentrations were obtained. This latter dose did not affect retinal concentrations of serotonin (5-HT), 5-hydroxyindole acetic acid (5-HIAA) and norepinephrine (NE). These results demonstrate that selective reductions of retinal dopamine and its metabolites can be obtained with a single intravitreal injection of 300 micrograms 6-OHDA in rabbits. The observed concomitant increase in B-wave amplitudes lends support to the hypothesis that DA acts as a mediator of lateral inhibition in the retina.     

rAAV-mediated nigral human parkin over-expression partially ameliorates motor deficits via enhanced dopamine neurotransmission in a rat model of Parkinson's disease

We hypothesized that over-expressing the E3 ligase, parkin, whose functional loss leads to Parkinson's disease, in the nigrostriatal tract might be protective in the unilateral 6-hydroxydopamine (6-OHDA) rat lesion model. Recombinant adeno-associated virus (rAAV) encoding human parkin or green fluorescent protein (GFP) was injected into the rat substantia nigra 6 weeks prior to a four-site striatal 6-OHDA lesion. Vector-mediated parkin over-expression significantly ameliorated motor deficits as measured by amphetamine-induced rotational behavior and spontaneous behavior in the cylinder test but forelimb akinesia as assessed by the stepping test was unaffected. rAAV-mediated human parkin was expressed in the nigrostriatal tract, the substantia pars reticulata, and the subthalamic nucleus. However, in lesioned animals, there was no difference between nigral parkin and GFP-transduction on lesion-induced striatal tyrosine hydroxylase (TH) innervation or nigral TH positive surviving neurons. A second lesion experiment was performed to determine if striatal dopamine (DA) neurotransmission was enhanced as measured biochemically. In this second group of parkin and GFP treated rats, behavioral improvement was again observed. In addition, striatal TH and DA levels were slightly increased in the parkin-transduced group. In a third experiment, we evaluated parkin and GFP transduced rats 6 weeks after vector injection without DA depletion. When challenged with amphetamine, parkin treated rats tended to display asymmetries biased away from the treated hemisphere. Nigral parkin over-expression induced increases in both striatal TH and DA levels. Therefore, while parkin over-expression exerted no protective effect on the nigrostriatal DA system, parkin appeared to enhance the efficiency of nigrostriatal DA transmission in intact nigral DA neurons likely due to the observed increases in TH.