Calcitriol Protection against Dopamine Loss Induced by Intracerebroventricular Administration of 6-Hydroxydopamine

Calcitriol has been implicated as an agent that has neuroprotective effects in various animal models of diseases, possibly by upregulating glial cell line-derived neurotrophic factor (GDNF). The present study examined the neuroprotective effects of calcitriol in a model of early Parkinson’s disease. Rats were treated daily with calcitriol or saline for 7 days before an intraventricular injection of 6-hydroxydopamine (6-OHDA), and then for 1 day or daily for 3½ to 4 weeks after lesioning. Evoked overflow and tissue content of dopamine (DA) were determined 3½ to 4 weeks post lesion. The 8-day calcitriol treatment did not attenuate 6-OHDA-induced decreases in evoked overflow of DA, nor did it protect against 6-OHDA-induced reductions in tissue levels of DA in the striatum or substantia nigra. However, the long-term calcitriol treatment did significantly increase evoked overflow of DA, as well as the amount of DA in the striatum, compared to saline treated animals. GDNF was significantly increased in the substantia nigra, but not in the striatum, of non-lesioned, calcitriol treated rats. These results suggest that long-term treatment with calcitriol can provide partial protection for dopaminergic neurons against the effects of intraventricularly administered 6-OHDA.     

Effects of Zingerone [4-(4-Hydroxy-3-Methoxyphenyl)-2-Butanone] and Eugenol [2-Methoxy-4-(2-Propenyl)Phenol] on the Pathological Progress in the 6-Hydroxydopamine-Induced Parkinson’s Disease Mouse Model

Parkinson’s disease (PD) is characterized by progressive degeneration of dopaminergic neurons in the nigrostriatal system and dopamine (DA) depletion in the striatum. The most popular therapeutic medicine for treating PD, 3-(3,4-Dihydroxyphenyl)-l-alanine (L-DOPA), has adverse effects, such as dyskinesia and disease acceleration. As superoxide (·O₂ ⁻) and hydroxyl radical (·OH) have been implicated in the pathogenesis of PD, free radical scavenging and antioxidants have attracted attention as agents to prevent disease progression. Rodents injected with 6-hydroxydopamine (6-OHDA) intracerebroventricularly are considered to be a good animal model of PD. Zingerone and eugenol, essential oils extracted from ginger and cloves, are known to have free radical scavenging and antioxidant effects. Therefore, we examined the effects of zingerone and eugenol on the behavioral problems in mouse model and on the DA concentration and antioxidant activities in the striatum after 6-OHDA administration and L-DOPA treatment. Daily oral administration of eugenol/zingerone and injection of L-DOPA intraperitoneally for 4 weeks following a single 6-OHDA injection did not improve abnormal behaviors induced by L-DOPA treatment. 6-OHDA reduced the DA level in the striatum; surprisingly, zingerone and eugenol enhanced the reduction of striatal DA and its metabolites. Zingerone decreased catalase activity, and increased glutathione peroxidase activity and the oxidized L-ascorbate level in the striatum. We previously reported that pre-treatment with zingerone or eugenol prevents 6-OHDA-induced DA depression by preventing lipid peroxidation. However, the present study shows that post-treatment with these substances enhanced the DA decrease. These substances had adverse effects dependent on the time of administration relative to model PD onset. These results suggest that we should be wary of ingesting these spice elements after the onset of PD symptoms.     

Zingerone [4-(4-hydroxy-3-methoxyphenyl)-2-butanone] Prevents 6-Hydroxydopamine-induced Dopamine Depression in Mouse Striatum and Increases Superoxide Scavenging Activity in Serum

As superoxide (·O₂^–) and hydroxyl radical (·OH) have been implicated in pathogenesis of Parkinsons disease, free radical scavenging, antioxidant, and neuroprotective agents have attracted attention as ways to prevent progression. We examined effects of zingerone, an alkaloid extracted from ginger root, on 6-hydroxydopamine (6-OHDA)-induced dopamine (DA) reduction in mouse striatum. Zingerone administration 1 h before and for 6 more days following one intracerebroventricular 6-OHDA injection prevented reductions of striatal DA and its metabolites, and increased serum ·O₂^– scavenging activity. Zingerone did not change activities of catalase or glutathione peroxidase in striatum or serum, or ·O₂^– scavenging activity in striatum. Treatment with diethyldithiocarbamate, SOD inhibitor, abolished the protective effect of zingerone against 6-OHDA-induced DA reduction. In vitro, zingerone scavenged ·O₂^– and ·OH and suppressed lipid peroxidation only weakly. Thus, direct antioxidant effects may be a minor component of its putative neuroprotective effect; instead, zingerone acted mainly by increasing systemic superoxide dismutase activity. Effects of zingerone treatment in this model suggest possible value in treatment of Parkinsons disease.     

Anti-apoptotic and Anti-inflammatory effect of Piperine on 6-OHDA induced Parkinson's Rat model

In the present study, we examined the molecular mechanism by which Piperine (bioactive compound of Piper nigrum) inhibits neuronal cell apoptosis. We further investigated the anti-inflammatory effect of Piperine on 6-OHDA induced Parkinson's disease. Consistent with its antioxidant properties, Piperine (10 mg/kg bwt) reduced 6-OHDA-induced lipid peroxidation and stimulated glutathione levels in striatum of rats. Furthermore, Piperine treatment diminished cytochrome-c release from mitochondria and reduced caspase-3 and caspase-9 activation induced by 6-OHDA. Treatment with Piperine markedly inhibited poly(ADP-ribose) polymerase activation, pro-apoptotic Bax levels and elevation of Bcl-2 levels. Piperine reduces contralateral rotations induced by apomorphine. Further narrow beam test and rotarod also showed improvement in motor coordination and balance behavior in rats treated with Piperine. In addition Piperine depletes inflammatory markers, TNF-α and IL-1β in 6-OHDA-induced Parkinson's rats. We propose that, in addition to its antioxidant properties Piperine exerts a protective effect via anti-apoptotic and anti-inflammatory mechanism on 6-OHDA induced Parkinson's disease.     

Probucol Affords Neuroprotection in a 6-OHDA Mouse Model of Parkinson’s Disease

Parkinson’s disease (PD) is a neurodegenerative disorder characterized by the degeneration of dopaminergic nigrostriatal neurons. Although the etiology of the majority of human PD cases is unknown, experimental evidence points to oxidative stress as an early and causal event. Probucol is a lipid-lowering phenolic compound with anti-inflammatory and antioxidant properties that has been recently reported as protective in neurotoxicity and neurodegeneration models. This study was designed to investigate the effects of probucol on the vulnerability of striatal dopaminergic neurons to oxidative stress in a PD in vivo model. Swiss mice were treated with probucol during 21 days (11.8 mg/kg; oral route). Two weeks after the beginning of treatment, mice received a single intracerebroventricular (i.c.v.) infusion of 6-hydroxydopamine (6-OHDA). On the 21st day, locomotor performance, striatal oxidative stress-related parameters, and striatal tyrosine hydroxylase and synaptophysin levels, were measured as outcomes of toxicity. 6-OHDA-infused mice showed hyperlocomotion and a significant decrease in striatal tyrosine hydroxylase (TH) and synaptophysin levels. In addition, 6-OHDA-infused mice showed reduced superoxide dismutase activity and increased lipid peroxidation and catalase activity in the striatum. Notably, probucol protected against 6-OHDA-induced hyperlocomotion and striatal lipid peroxidation, catalase upregulation and decrease of TH levels. Overall, the present results show that probucol protects against 6-OHDA-induced toxicity in mice. These findings may render probucol as a promising molecule for further pharmacological studies on the search for disease-modifying treatment in PD.     

Molecular Profiling of a 6-Hydroxydopamine Model of Parkinson’s Disease

Convection enhanced delivery of 6-hydroxydopamine (6-OHDA) to the rat striatum results in a model of Parkinson’s disease. An important feature of this unilateral model is the progressive loss of dopaminergic (DA) neurons over the course of several weeks. To improve the understanding of this model, gene expression changes in the substantia nigra, which contains the DA neuron cell bodies, and the striatum, which contains the DA neuron synaptic terminals, were examined using DNA microarrays. Samples were collected and behavior was analyzed from vehicle and toxin treated animals at 3 days, 1 week, 2 weeks and 4 weeks following 6-OHDA treatment. Tissue DA content was determined and samples from animals which exhibited a substantial depletion of striatal DA were included in the subsequent gene expression analysis. The results of the gene expression analysis indicated that 6-OHDA elicits a vigorous inflammatory response, comprised of several distinct pathways, in the striatum at the earliest time point tested. In contrast, relatively few gene expression changes were observed in the SN at the 3-day time point. In both tissues examined there was evidence for a vigorous inflammatory response at the 1- and 2-week time points, which was substantially diminished by the 4-week time point. Inflammation plays a prominent role in the 6-OHDA model of Parkinson’s disease.     

Human albumin prevents 6-hydroxydopamine-induced loss of tyrosine hydroxylase in in vitro and in vivo

Human albumin has recently been demonstrated to protect brain neurons from injury in rat ischemic brain. However, there is no information available about whether human albumin can prevent loss of tyrosine hydroxylase (TH) expression of dopaminergic (DA) neurons induced by 6-hydroxydopamine (6-OHDA) toxicity that is most commonly used to create a rat model of Parkinson's disease (PD). In the present study, two microliters of 1.25% human albumin were stereotaxically injected into the right striatum of rats one day before or 7 days after the 6-OHDA lesion in the same side. D-Amphetamine-induced rotational asymmetry was measured 7 days, 3 and 10 weeks after 6-OHDA lesion. We observed that intrastriatal administration of human albumin significantly reduced the degree of rotational asymmetry. The number of TH-immunoreactive neurons present in the substantia nigra was greater in 6-OHDA lesioned rats following human albumin-treatment than non-human albumin treatment. TH-immunoreactivity in the 6-OHDA-lesioned striatum was also significantly increased in the human albumin-treated rats. To examine the mechanisms underlying the effects of human albumin, we challenged PC12 cells with 6-OHDA as an in vitro model of PD. Incubation with human albumin prevented 6-OHDA-induced reduction of cell viability in PC12 cell cultures, as measured by MTT assay. Furthermore, human albumin reduced 6-OHDA-induced formation of reactive oxygen species (ROS) and apoptosis in cultured PC12 cells, as assessed by flow cytometry. Western blot analysis showed that human albumin inhibited 6-OHDA-induced activation of JNK, c-Jun, ERK, and p38 mitogen-activated protein kinases (MAPK) signaling in PC12 cultures challenged with 6-OHDA. Human albumin may protect against 6-OHDA toxicity by influencing MAPK pathway followed by anti-ROS formation and anti-apoptosis.     

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.     

Striatal Dopaminergic Fiber Recovery After Acute <Emphasis Type="SmallCaps">l</Emphasis>-DOPA Treatment in 6-Hydroxydopamine (6-OHDA) Lesioned Rats

In order to examine the acute effects of l-DOPA treatment following 6-hydroxydopamine (6-OHDA) injection into rat medial forebrain bundle (MFB). Sprague–Dawley rats (n = 48) received either 6-OHDA, via intracranial unilateral injection, into the MFB (experimental group) or saline 0.9% (control group). Administration of l-DOPA or saline 0.9% began 1 month after the 6-OHDA injection for 10 consecutive days. Within 3 days, an increase in the density of striatal tyrosine hydroxylase (TH) immunoreactive fibers within the striatum, when compared to the control group was observed. There was no difference in the loss of substantia nigra pars compacta (SNpc) dopaminergic (DA) neurons between. The greater density of TH fibers in the striatum following l-DOPA may be related to recovery of the DA phenotype and/or sprouting of TH axon terminals. Only animals with severe cell loss in the SNpc experienced abnormal involuntary movements (AIMs) or “dyskinesias” in response to l-DOPA, which did not correlate with striatal TH fiber density, suggesting that induction of TH-positive fibers does not contribute to the occurrence of dyskinesia. The relationship between cell loss, fiber density and AIM to the abundance of markers of microglial activation were also examined. Iba-1, a microglial marker, immunoreactivity was not affected by l-DOPA treatment, was not correlated with the severity of AIM indicating that microglial activation does not contribute to dyskinetic phenomena.     

Activin A Protects Midbrain Neurons in the 6-Hydroxydopamine Mouse Model of Parkinson’s Disease

Parkinson’s disease (PD) is a chronic neurodegenerative disease characterized by a significant loss of dopaminergic neurons within the substantia nigra pars compacta (SNpc) and a subsequent loss of dopamine (DA) within the striatum. Despite advances in the development of pharmacological therapies that are effective at alleviating the symptoms of PD, the search for therapeutic treatments that halt or slow the underlying nigral degeneration remains a particular challenge. Activin A, a member of the transforming growth factor β superfamily, has been shown to play a role in the neuroprotection of midbrain neurons against 6-hydroxydopamine (6-OHDA) in vitro, suggesting that activin A may offer similar neuroprotective effects in in vivo models of PD. Using robust stereological methods, we found that intrastriatal injections of 6-OHDA results in a significant loss of both TH positive and NeuN positive populations in the SNpc at 1, 2, and 3 weeks post-lesioning in drug naïve mice. Exogenous application of activin A for 7 days, beginning the day prior to 6-OHDA administration, resulted in a significant survival of both dopaminergic and total neuron numbers in the SNpc against 6-OHDA-induced toxicity. However, we found no corresponding protection of striatal DA or dopamine transporter (DAT) expression levels in animals receiving activin A compared to vehicle controls. These results provide the first evidence that activin A exerts potent neuroprotection in a mouse model of PD, however this neuroprotection may be localized to the midbrain.     

The effects of pergolide on memory and oxidative stress in a rat model of Parkinson’s disease

One of the most widely used animal models of Parkinson’s disease (PD) involves injecting 6-hydroxydopamine (6-OHDA) directly into the substantia nigra (SN). Some recent reports speculated that dopaminergic drugs may exert brain antioxidant activity, which could explain some of their protective actions. In this way, the aim of the present study was to examine the effects of low-dose pergolide on memory deficits and brain oxidative stress in a 6-OHDA-induced rat model of PD. Right-unilateral lesions of the SN were produced with 6-OHDA. Two weeks after neurosurgery, pergolide (0.3 mg/kg/day) was injected intraperitoneally in the 6-OHDA + pergolide and sham-operated + pergolide groups, while sham-operated and 6-OHDA alone groups received saline. Radial-8-arm maze and Y-maze were used for memory assessment. We also determined some enzymatic antioxidant defenses like superoxide dismutase or glutathione peroxidase and a lipid peroxidation marker [malondialdehyde (MDA)], from the temporal lobe. A reduced number of working/reference memory errors was observed in 6-OHDA + pergolide group, compared to sham-operated rats. Additionally, post hoc analysis showed significant differences between 6-OHDA and 6-OHDA + pergolide groups in both Y-maze and radial-arm-maze tasks. We also noted a significant decrease of MDA level in the 6-OHDA + pergolide group, compared to sham-operated rats. Significant correlations were also found between behavioral parameters and MDA levels. Our data suggest that pergolide facilitates spatial memory and improves brain oxidative balance, after a 6-OHDA-induced model of PD. This could be useful for further investigations and clinical applications of pergolide.     

Effects of aluminum and zinc on the oxidative stress caused by 6-hydroxydopamine autoxidation: relevance for the pathogenesis of Parkinson's disease

Aluminum and zinc have been related to the pathogenesis of Parkinson's disease (PD), the former for its neurotoxicity and the latter for its apparent antioxidant properties. 6-Hydroxydopamine (6-OHDA) is an important neurotoxin putatively involved in the pathogenesis of PD, its neurotoxicity often being related to oxidative stress. The potential effect of these metals on the oxidative stress induced by 6-OHDA autoxidation and the potential of ascorbic acid (AA), cysteine, and glutathione to modify this effect were investigated. Both metals, particularly Al3+, induced a significant reduction in *OH production by 6-OHDA autoxidation. The combined action of AA and a metal caused a significant and sustained increase in *OH generation, particularly with Al3+, while the effect of sulfhydryl reductants was limited to only the first few minutes of the reaction. However, both Al3+ and Zn2+ provoked a decrease in the lipid peroxidation induced by 6-OHDA autoxidation using mitochondrial preparations from rat brain, assessed by TBARS formation. In the presence of AA, only Al3+ induced a significant reduction in lipid peroxidation. After intrastriatal injections of 6-OHDA in rats, tyrosine hydroxylase immunohistochemistry revealed that Al3+ reduces 6-OHDA-induced dopaminergic lesion in the striatum, which corroborates the involvement of lipid peroxidation in 6-OHDA neurotoxicity and appears to discard the participation of this mechanism on PD by Al3+ accumulation. The previously reported antioxidant properties of Zn2+ appear to be related to the induction of Zn2+-containing proteins and not to the metal per se.     

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.     

Alcoholic Extract of Bacopa monniera Linn. Protects Against 6-Hydroxydopamine-Induced Changes in Behavioral and Biochemical Aspects: A Pilot Study

Parkinson's disease is one of the commonest neurodegenerative diseases, and oxidative stress has been evidenced to play a vital role in its causation. In this study, we evaluated whether alcoholic extract of Bacopa monniera (AEBM), an antioxidant and memory enhancer can slow the neuronal injury in a 6-OHDA-rat model of Parkinson's. Rats were treated with 20 and 40?mg/kg bodyweight of AEBM for 3?weeks. On Day 21, 2?μl of 6-OHDA (12?μg in 0.01?% in ascorbic acid-saline) was infused into the right striatum, while the control group received 2?μl of vehicle. Three weeks after the 6-OHDA injection, the rats were tested for neurobehavioral activity (rotarod, locomotor activity, grip test, forced swim test, radial arm maze) and were killed after 6?weeks for the estimation of lipid peroxidation, reduced glutathione (GSH) content, activities of glutathione-S-transferase, glutathione reductase, glutathione peroxidase, superoxide dismutase (SOD), and catalase (CAT). The deficits in behavioral activity due to 6-OHDA lesioning were significantly and dose dependently restored by AEBM. Lesioning was followed by an increased lipid peroxidation and significant depletion of reduced GSH content in the substantia nigra, which was prevented with AEBM pretreatment. The activities of GSH-dependent enzymes, CAT and SOD in striatum were reduced significantly by lesioning, which were restored significantly and dose dependently by AEBM. This study indicates that the extract of B.?monniera might be helpful in attenuating 6-OHDA-induced lesioning in rats.     

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.     

Dissociation of progressive dopaminergic neuronal death and behavioral impairments by Bax deletion in a mouse model of Parkinson's diseases

Parkinson's disease (PD) is a common, late-onset movement disorder with selective degeneration of dopaminergic (DA) neurons in the substantia nigra (SN). Although the neurotoxin 6-hydroxydopamine (6-OHDA) has been used to induce progressive degeneration of DA neurons in various animal models of PD, the precise molecular pathway and the impact of anti-apoptotic treatment on this neurodegeneration are less understood. Following a striatal injection of 6-OHDA, we observed atrophy and progressive death of DA neurons in wild-type mice. These degenerating DA neurons never exhibited signs of apoptosis (i.e., caspase-3 activation and cytoplasmic release of cytochrome C), but rather show nuclear translocation of apoptosis-inducing factor (AIF), a hallmark of regulated necrosis. However, mice with genetic deletion of the proapoptotic gene Bax (Bax-KO) exhibited a complete absence of 6-OHDA-induced DA neuron death and nuclear translocation of AIF, indicating that 6-OHDA-induced DA neuronal death is mediated by Bax-dependent AIF activation. On the other hand, DA neurons that survived in Bax-KO mice exhibited marked neuronal atrophy, without significant improvement of PD-related behavioral deficits. These findings suggest that anti-apoptotic therapy may not be sufficient for PD treatment, and the prevention of Bax-independent neuronal atrophy may be an important therapeutic target.     

Catechin attenuates 6-hydroxydopamine (6-OHDA)-induced cell death in primary cultures of mesencephalic cells

Past studies have shown the protective effects of tea catechins on oxidative cell damage induced by 6-OHDA in PC12 cells. In this study we verified whether or not catechin prevents 6-OHDA-induced oxidative cell damage in primary cultures of rat mesencephalic cells. On exposure to 6-OHDA (200 microM), the cultures showed a marked decrease in cell viability, disturbances in lipid peroxidation, and an increased generation of NO, as assayed by MTT, TBARS and nitrite assays, respectively. Introduction of catechin significantly attenuated the cell death caused by 6-OHDA at concentrations of 3.4, 34 and 340 microM in a dose-related manner. Catechin produced no marked changes on 6-OHDA-induced increases in NO, but caused a significant inhibition of lipid peroxidation. These results suggest that catechins offer similar cytoprotection against 6-OHDA-induced oxidative cell damage in mesencephalic cell cultures, as previously described in PC12 cells. The cytoprotective function of catechin results from its antioxidant property and is not due to the inhibition of nitric oxide synthase. These findings further support and substantiate traditional consumption of catechin rich green/black tea as protection against neurodegenerative diseases like Parkinsonism.     

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。     

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.     

Neuroprotective Effects of Chalcones from <Emphasis Type="Italic">Myracrodruon urundeuva</Emphasis> on 6-Hydroxydopamine-Induced Cytotoxicity in Rat Mesencephalic Cells

In the present work, we showed that a chalcone-enriched fraction (CEF) isolated from the stem bark of a Brazilian medicinal plant, Myracrodruon urundeuva, presents neuroprotective actions on 6-hydroxydopamine (6-OHDA)-induced neuronal cell death, in rat mesencephalic cells. In the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium] assay, which is an index of cell viability, CEF (1–100 μg/ml) reversed in a concentration-dependent manner the 6-OHDA-induced cell death. While cells exposed to 6-OHDA (40 μM) showed an increased concentration of thiobarbituric acid reactive substances (TBARS), the pretreatment with CEF (10–100 μg/ml) significantly decreased the 6-OHDA-induced TBARS formation, indicative of a neuroprotection against lipoperoxidation. Furthermore, the drastic increase of nitrite levels induced by 6-OHDA, indicative of nitric oxide formation and free radicals production, was prevented by CEF. Double staining with acridine orange/ethidium bromide showed that cultures exposed to 6-OHDA (40 and 200 μM) presented an increase of apoptotic and necrotic cell numbers in a concentration-dependent manner. CEF (100 μg/ml) protected cells from apoptosis and necrosis and increased number of cells presenting a normal morphology. The immunohistochemical analysis for tyrosine hydroxylase (TH) positive neurons indicated that 6-OHDA (40 and 200 μM) caused a concentration-dependent loss of TH+ and TH− neurons. CEF protected both cells types from 6-OHDA-induced cell death. All together, our results demonstrated neuroprotective effects of chalcones, which are able to reduce oxidative stress and apoptotic injury caused by 6-OHDA. Our findings suggest that chalcones could provide benefits, along with other therapies, in neurodegenerative injuries, such as Parkinson’s disease.