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).     

Curcumin protects nigrostriatal dopaminergic neurons and reduces glial activation in 6-hydroxydopamine hemiparkinsonian mice model

This study investigated the effects of curcumin on nigrostriatal dopaminergic (DA) neurons and glial response in 6-hydroxydopamine (6-OHDA) hemiparkinsonian mice. Following unilateral intrastriatal 6-OHDA injection, mice were daily injected with curcumin for seven days, beginning on the day of lesion. Seven days after 6-OHDA lesioning, sections from the striatum and the substantia nigra pars compacta (SNpc) were collected and immunohistochemically stained for DA neurons and reactive glia. Curcumin decreased 6-OHDA-induced loss of nigral tyrosine hydroxylase-immunoreactive (TH-IR) neurons and striatal TH-IR fibers. The neuroprotection was coincided with a significant attenuation of microglial and astroglial reaction in the SNpc and the striatum. These results suggest that the neuroprotective effects of curcumin in 6-OHDA-lesioned mice may be mediated through its anti-inflammatory properties or direct protection on nigral DA neurons, thereby reducing neuronal injury-induced glial activation.     

Parkinson's disease: changes in apoptosis-related factors suggesting possible gene therapy

Summary. Specific degeneration of the nigrostriatal dopamine (DA) neurons of the substantia nigra pars compacta and the resulting loss of nerve terminals accompanied by DA deficiency in the striatum are responsible for most of the movement disturbances called parkinsonism, i.e., muscle rigidity, akinesia, and resting tremor, observed in Parkinson's disease (PD). We and other workers have found changes in the levels of cytokines, neurotrophins, and other apoptosis-related factors in the nigro-striatal region of postmortem brain and/or in the cerebrospinal fluid (CSF) from PD patients, or from animal models of PD such as 1-methyl-4-phenyl-1,2,3,4-tetrahydropyridine (MPTP)-induced PD in mice or 6-hydroxydopamine (6-OHDA)-induced PD in rats. The most remarkable changes observed specifically in the nigrostriatal region were decreased levels of neurotrophins supporting DA neurons. These results indicate that the process of cell death in the nigrostriatal DA neurons in PD may be the so-called programmed cell death, i.e., apoptosis. Thus gene therapy for PD should aim both at supplementing the decreased striatal DA level by introducing the genes of DA-synthesizing enzymes into non-DA cells in the striatum and at supporting or restoring DA neurons by preventing apoptosis by introducing genes that block the process of apoptosis. Received January 15, 2002; accepted January 17, 2002     

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.     

Distribution and localization patterns of estrogen receptor-beta and insulin-like growth factor-1 receptors in neurons and glial cells of the female rat substantia nigra: localization of ERbeta and IGF-1R in substantia nigra

Although several studies have focused on the neuroprotective effects of estrogen (E2) on stroke, there have been tantalizing reports on the potential neuroprotective role of E2 in degenerative neuronal diseases such as Alzheimer's and Parkinson's (PD). In animal models of PD, E2 protects the nigrostriatal dopaminergic (DA) system against neurotoxins. However, little is known about the cellular and molecular mechanism(s) involved by which E2 elicits its neuroprotective effects on the nigrostriatal DA system. A preferred mechanism for neuroprotection is the interaction of E2 with specific neuroprotective growth factors and receptors. One such neuroprotective factor/receptor system is insulin-like growth factor-1 (IGF-1). E2 neuroprotective effects in the substantia nigra (SN) DA system have been shown to be dependent on IGF-1. To determine whether E2 also interacts with the IGF-1 receptor (IGF-1R) and to determine the cellular localization of estrogen receptor (ER) and IGF-1R, we compared the distribution of ER and IGF-1R in the SN. Stereological measurements revealed that 40% of the subpopulation of tyrosine hydroxylase-immunoreactive (TH-ir) SN pars compacta (SNpc) DA neurons are immunoreactive for estrogen receptor-beta (ERbeta). No immunolabeling for ERalpha was observed. In situ hybridization and immunocytochemistry studies confirmed the expression of IGF-1R mRNA and revealed that almost all TH-ir SNpc DA neurons were immunoreactive for IGF-1R, respectively. Moreover, one-third of glial fibrillary acidic protein (GFAP-ir) cells in the SN were ERbeta-ir, and 67% of GFAP-ir cells expressed IGF-1R-ir. Therefore, the localization of ERbeta and IGF-1R on SNpc DA neurons and astrocytes suggests a modulatory role of E2 on IGF-1R, and this modulation may affect neuroprotection.     

N-terminal tripeptide of IGF-1 (GPE) prevents the loss of TH positive neurons after 6-OHDA induced nigral lesion in rats

The effect of the N-terminal tripeptide of insulin-like growth factor (IGF)-1, glycine-proline-glutamate (GPE), as a neuroprotective agent for nigro-striatal dopaminergic neurons was examined in the present study using a rat model of Parkinson's disease. A unilateral nigro-striatal lesion was induced in rats by injecting 6-hydroxydopamine (6-OHDA) into the right medial forebrain bundle (MFB). GPE (3 microgram) or its vehicle was administered intracerebroventricularly (i.c.v.) 2 h after the 6-OHDA lesion. Tyrosine-hydroxylase (TH) immunohistochemistry in the substantia nigra compacta (SNc) and the striatum were examined 2 weeks after the lesion. Following 6-OHDA injection, the number of TH immunopositive neurons in the ipsilateral SNc was reduced. The density of TH immunostaining was also reduced in the ipsilateral SNc and the striatum. Treatment with a single dose of GPE (n=9) significantly prevented the loss of TH immunopositive neurons (p<0. 001) and restored the TH immunoreactivity in both the SNc and the striatum compared with the vehicle control group (n=9, p<0.001). The results suggest that GPE showed promise as a potential treatment for Parkinson's disease.     

尼古丁对帕金森病大鼠纹状体GDNF和多巴胺含量的影响

目的 研究尼古丁对帕金森病（PD）大鼠纹状体脑胶质细胞源性神经营养因子(GDNF)和多巴胺（DA）含量的影响。方法 将6－羟多巴胺（6－OHDA）立体定向注射到大鼠右侧中脑腹侧背盖部（VTA）和黑质致密部（SNpc)，建立PD大鼠模型。采用生化、免疫组织化学方法观察不同剂量尼古丁对PD大鼠的作用，检测纹状体GDNF表达及DA含量的变化。结果 造模前及造模后皮下注射尼古丁的PD大鼠，纹状体GDNF表达及DA含量较PD组有明显改善（P＜0．05）。结论 尼古丁可减轻6－OHDA对黑质DA能神经元的损伤，对PD大鼠具有保护作用。     

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.     

Effect of 6-hydroxydopamine treatment on kynurenine aminotransferase-I (KAT-I) immunoreactivity of neurons and glial cells in the rat substantia nigra

Parkinson’s disease (PD), a progressive neurodegenerative disorder, is characterized by a preferential loss of dopaminergic neurons in the substantia nigra pars compacta (SNPC). Neurons in the SNPC are known to express tyrosine hydroxylase (TH); therefore, in a commonly used PD model, 6-hydroxydopamine (6-OHDA), a selective catecholamine neurotoxin, induces neuronal death in SNPC. We have shown with immunohistochemical techniques that kynurenine aminotransferase-I (KAT-I), the enzyme taking part in the formation of kynurenic acid (KYNA)—the only known endogenous selective NMDA receptor antagonist and a potent neuroprotective agent—is also expressed in the rat SNPC. We found that KAT-I and TH co-exist in the very same neurons of SNPC and that 6-OHDA injected into the lateral ventricle produced loss of the majority of nigral neurons. Densitometric analysis proved that, in consequence of 6-OHDA treatment, not only TH but also KAT-I immunoreactivity diminished considerably in the remaining SNPC neurons. Astrocytes in the substantia nigra were found to express KAT-I under normal conditions; the amount of this enzyme increased after administration of 6-OHDA, whereas microglial cells became KAT-I immunoreactive only after 6-OHDA treatment. Since intrinsic KYNA in SNPC neurons is perceptibly insufficient to protect them from the deleterious effect of 6-OHDA, it is hypothesized that biochemical approaches which increase KYNA content of the central nervous system might prevent the deleterious effect of 6-OHDA and, supposedly, also the neuronal degradation characterizing PD.     

被动吸烟对大鼠纹状体多巴胺及黑质自由基含量的影响

目的研究被动吸烟对帕金森病(PD)大鼠的影响,探讨其作用机制。方法通过6-羟多巴胺(6-O-HDA)脑立体定向注射术建立大鼠PD模型。术前4周开始被动吸烟及术后持续2周为预防组;术后3周给予被动吸烟持续2周为治疗组。采用生化的方法观察PD大鼠纹状体黑质自由基、抗氧化剂及多巴胺含量的变化。结果吸烟治疗组和吸烟预防组大鼠黑质自由基及抗自由基酶较对照组有明显改善(P<0.05);吸烟预防组PD大鼠纹状体DA含量较对照组有明显改善(P<0.05);吸烟治疗组PD大鼠纹状体DA含量较对照组无变化(P>0.05)。结论被动吸烟能减轻黑质纹状体DA能神经元的损伤。     

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.     

NAIP protects the nigrostriatal dopamine pathway in an intrastriatal 6-OHDA rat model of Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder of the basal ganglia, associated with the inappropriate death of dopaminergic neurons of the substantia nigra pars compacta (SNc). Here, we show that adenovirally mediated expression of neuronal apoptosis inhibitor protein (NAIP) ameliorates the loss of nigrostriatal function following intrastriatal 6-OHDA administration by attenuating the death of dopamine neurons and dopaminergic fibres in the striatum. In addition, we also addressed the role of the cysteine protease caspase-3 activity in this adult 6-OHDA model, because a role for caspases has been implicated in the loss of dopamine neurons in PD, and because NAIP is also a reputed inhibitor of caspase-3. Although caspase-3-like proteolysis was induced in the SNc dopamine neurons of juvenile rats lesioned with 6-OHDA and in adult rats following axotomy of the medial forebrain bundle, caspase-3 is not induced in the dopamine neurons of adult 6-OHDA-lesioned animals. Taken together, these results suggest that therapeutic strategies based on NAIP may have potential value for the treatment of PD.     

Changes in cytokines and neurotrophins in Parkinson's disease

Degeneration of the dopamine (DA) neurons of the substantia nigra pars compacta and the resulting loss of nerve terminals accompanied by DA deficiency in the striatum are responsible for most of the movement disturbances called parkinsonism, observed in Parkinson's disease (PD). One hypothesis of the cause of degeneration of the nigrostriatal DA neurons is that PD is caused by programmed cell death (apoptosis) due to increased levels of cytokines and/or decreased ones of neurotrophins. We and other workers found markedly increased levels of cytokines, such as tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-2, IL-4, IL-6, transforming growth factor (TFG)-alpha, TGF-beta1, and TGF-beta2, and decreased ones of neurotrophins, such as brain-derived neurotrophic factor (BDNF) and nerve growth factor (NGF), in the nigrostriatal DA regions and ventricular and lumbar cerebrospinal fluid of PD patients. Furthermore, the levels of TNF-alpha receptor R1 (TNF-R1, p55), bcl-2, soluble Fas (sFas), and the activities of caspase-1 and caspase-3 were also elevated in the nigrostriatal DA regions in PD. In experimental animal models of PD, IL-1beta level was increased and NGF one decreased in the striatum of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced parkinsonian mice, and TNF-alpha level was increased in the substantia nigra and striatum of the 6-hydroxydopamine (6OHDA)-injected side of hemiparkinsonian rats. L-DOPA alone or together with 6OHDA does not increase the level of TNF-alpha in the brain in vivo. Increased levels of proinflammatory cytokines, cytokine receptors and caspase activities, and reduced levels of neurotrophins in the nigrostriatal region in PD patients, and in MPTP- and 6OHDA-produced parkinsonian animals suggest increased immune reactivity and programmed cell death (apoptosis) of neuronal and/or glial cells. These data indicate the presence of such proapoptotic environment in the substantia nigra in PD that may induce increased vulnerability of neuronal or glial cells towards a variety of neurotoxic factors. The probable causative linkage among the increased levels of proinflammatory cytokines and the decreased levels of neurotrophins, candidate parkinsonism-producing neurotoxins such as isoquinoline neurotoxins (Review; Nagatsu, 1997), and the genetic susceptibility to toxic factors, remains for further investigation in the molecular mechanism of PD. The increased cytokine levels, decreased neurotrophin ones, and the possible immune response in the nigrostriatal region in PD indicate new neuroprotective therapy including nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin, immunosuppressive or immunophilin-binding drugs such as FK-506, and drugs increasing neurotrophins.     

JNK Inhibition Protects Dopamine Neurons and Provides Behavioral Improvement in a Rat 6-hydroxydopamine Model of Parkinson's Disease

Parkinson's disease (PD) results from the loss of dopamine neurons located in the substantia nigra pars compacta (SNpc) that project to the striatum. A therapeutic has yet to be identified that halts this neurodegenerative process, and as such, development of a brain penetrant small molecule neuroprotective agent would represent a significant advancement in the treatment of the disease. To fill this void we developed an aminopyrimidine JNK inhibitor (SR-3306) that reduced the loss of dopaminergic cell bodies in the SNpc and their terminals in the striatum produced by unilateral injection of 6-hydroxydopamine (6-OHDA) into the nigrostriatal pathway. Administration of SR-3306 [10 mg/kg/day (s.c.) for 14 days] increased the number of tyrosine hydroxylase immunoreactive (TH(+)) neurons in the SNpc by six-fold and reduced the loss of the TH(+) terminals in the striatum relative to the corresponding side of 6-OHDA-lesioned rats that received only vehicle (p<0.05). In addition, SR-3306 [10 mg/kg/day (s.c.) for 14 days] decreased d-amphetamine-induced circling by 87% compared to 6-OHDA-lesioned animals given vehicle. Steady-state brain levels of SR-3306 at day 14 were 347 nM, which was approximately two-fold higher than the cell-based IC(50) for this compound. Finally, immunohistochemical staining for phospho-c-jun (p-c-jun) revealed that SR-3306 [10 mg/kg/day (s.c.) for 14 days] produced a 2.3-fold reduction of the number of immunoreactive neurons in the SNpc relative to vehicle treated rats. Collectively, these data suggest that orally bioavailable JNK inhibitors may be useful neuroprotective agents for the treatment of Parkinson's disease.     

Failure of estrogen to protect the substantia nigra pars compacta of female rats from lesion induced by 6-hydroxydopamine

The immunostaining for tyrosine hydroxylase (TH) in the substantia nigra pars compacta (SNpc) and in the ventral tegmental area (VTA) after intranigral infusion of 6-hydroxydopamine (6-OHDA, 6 microg/side) was analyzed in ovariectomized adult female Wistar rats. Estrogen replacement for 52 days (400-microg 17-beta-estradiol capsules) did not prevent the loss of TH-immunoreactive cells induced by 6-OHDA in the SNpc. This result indicates that the neuroprotective effect of dopaminergic mesencephalic cells is not observed with long-term estrogen replacement.     

帕金森病大鼠模型黑质白介素-6表达的实验研究

目的探讨白介素-6(IL-6)和小胶质细胞在帕金森病发病机制中作用,阐述小胶质细胞激活后作用的合理模式。方法采用立体定向术将神经毒素6-羟基多巴(6-OHDA)注入大鼠右侧纹状体制作偏侧帕金森病大鼠模型。造模2月后,计数黑质致密部神经元和小胶质细胞数目,观察黑质致密部病理形态学变化,并采用免疫组织化学方法观察黑质致密部IL-6表达水平的变化。结果光镜下观察模型组右侧黑质致密部多巴胺能神经元几乎消失,小胶质细胞数目明显增多,与假手术组及正常对照组相比,差异有显著性(P<0.05)。免疫组化染色显示模型组右侧黑质致密部可见明显的小胶质细胞核周的棕褐色阳性表达,而模型组左侧与假手术组及正常对照组右侧黑质均未见明显阳性着染区。结论神经毒素6-OHDA可导致神经元释放小胶质细胞激活态物质,激活小胶质细胞释放IL-6介导细胞毒作用,促进神经元的慢性变性坏死。     

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.     

Stress reduces the neuroprotective effect of exercise in a rat model for Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disease of nigrostriatal dopamine (DA) neurons that project from the substantia nigra pars compacta (SNc) to the striatum. To further understand PD, researchers have developed standardized animal models of PD. In this study, Long Evans (LE) rats were unilaterally lesioned by injection of the neurotoxin, 6-hydroxydopamine (6-OHDA), into the medial forebrain bundle (MFB) of the left hemisphere. The rats were divided into three groups randomly; group 1 (runners) were housed in individual cages with attached running wheels, group 2 (stressed-runners) had access to individual free running wheels, except post-lesion when the rats were subjected to immobilization of the running wheel for 1 h per day for 14 days, as well as one session of 24-h food deprivation and a 7-h shift in the light/dark cycle. Group 3 (non-runnners) were housed individually in cages with attached running wheels that were permanently immobilized. Subcutaneous injection of the DA agonist, apomorphine, caused stressed-runners and non-runners to rotate vigorously away from the side of the lesion (contralaterally). Apomorphine-induced rotations provide a behavioural measure of the extent of the lesion, a depletion of more than 80% of DA neurons is required to produce vigorous contralateral rotations in response to apomorphine injection. Runners rotated significantly less than non-runners and stressed-runners. The number of rotations performed by stressed-runners was not significantly different from non-runners, suggesting that stress had cancelled the neuroprotective effect of running. Immunohistochemical staining for tyrosine hydroxylase in the SNc revealed slightly less destruction of DA neurons in the runners than in stressed-runners or non-runners, although these differences did not achieve statistical significance. The behavioural results confirm a previous finding suggesting that voluntary exercise is neuroprotective. A novel finding is that mild stressors cancel the neuroprotection afforded by voluntary exercise.     

6-OHDA诱导大鼠多巴胺神经元选择性缺失的研究

目的 电压依赖性钙离子通道分布对6-羟基多巴胺（6-OHDA）诱导的SD大鼠多巴胺能神经元缺失的影响.方法 6-OHDA单侧脑内内侧前脑束（MFB）立体定位注射,术后10d观测行为学变化;并取脑固定,免疫组化酪氨酸羟化酶（TH）染色观察中脑黑质致密部（SNc）与腹侧背盖区（VTA）多巴胺能神经元的凋亡情况.并应用膜片钳全细胞记录技术,测量SNc与VTA多巴胺能神经元的电压依赖性钙离子通道的电流密度.结果 损伤侧的SNc区TH阳性细胞与对侧比较明显减少,而VTA区TH阳性细胞与对侧相比变化较小;全细胞记录电压膜片钳技术测量,发现SNc多巴胺能神经元钙通道电流密度与VTA相比明显较高.结论 该结果的发现,提示钙离子通道可能参与到帕金森氏病中脑多巴胺能神经元的选择性凋亡的机制.