Intermittent administrations of dopaminergic agents in hemiparkinsonian rat enhances the behavioral response to subsequent administration of the drugs. This phenomenon is known as "priming" and thought as comparable to drug-induced dyskinesia in patients with Parkinson's disease. We investigated the behavioral and electrophysiological changes in 6-hydroxydopamine (6-OHDA)-lesioned hemiparkinsonian rats after repeated administrations of apomorphine. Administration of apomorphine (0.32 mg/kg, intraperitoneal, i.p.) twice daily for 6 days enhanced the rotation induced by apomorphine from 341 turns/hour at the beginning to 755 turns/hr at the end. At the same time, the response to selective D2 agonist quinpirole (0.26 mg/kg, i.p.) was also enhanced from 203 to 555 turns/hr. Extracellular single unit recording revealed no significant difference in the basal firing rates of substantia nigra pars reticulata (SNr) neurons between the ipsilateral and contralateral side of the 6-OHDA lesion regardless of the repeated administrations of apomorphine. In SNr of the lesion side, the units with burst firing pattern were found more frequently after repeated administrations of apomorphine and the suppressive effect of quinpirole on the firing rate was enhanced. These findings suggest that the increased percentage of the burst units is the important electrophysiological change in the development of enhanced response to selective D2 agonist.
Animal ; Apomorphine/*pharmacology ; Dopamine Agonists/*pharmacology ; MPTP Poisoning/physiopathology ; Male ; Oxidopamine/toxicity ; Parkinsonian Disorders/*physiopathology ; Quinpirole/pharmacology ; Rats ; Rats, Sprague-Dawley ; Receptors, Dopamine D2/*drug effects ; Substantia Nigra/*drug effects/physiology

Dopamine (DA) is an oxidant that may contribute to the degeneration of dopaminergic neurons. The present study demonstrates that DA-induced cytotoxicity in human-derived neurotypic cells, SH-SY5Y, is prevented by resveratrol, one of the major antioxidative constituents found in the skin of grapes. SH-SY5Y cells, a neuroblastoma cell line, treated with DA at 300 and 500 micrometer for 24 h underwent apoptotic death as determined by characteristic morphological features, including nuclear condensation, and loss of mitochondrial membrane potential (MMP). Flow cytometric analysis using Annexin V showed that DA can induce significant and severe apoptosis. Exposure to resveratrol (5 micrometer) for 1 h prior to the DA treatment attenuated DA-induced cytotoxicity, and rescued the loss of MMP. To investigate the apoptotic signaling pathways relevant to the restoration of DA-induced apoptosis by resveratrol, we carried out quantitative analysis of Bcl-2, caspase-3, and cleaved poly ADP-ribose polymerase (PARP) by immunoblot analysis. Resveratrol pretreatment led to a decrease in cleavage of PARP, an increase in the Bcl-2 protein, and activation of caspase-3. These results suggest that DA may be a potential oxidant of neuronal cells at biologically relevant concentrations. Resveratrol may protect SH-SY5Y cells against this cytotoxicity, reducing intracellular oxidative stress through canonical signal pathways of apoptosis and may be of biological importance in the prevention of a dopaminergic neurodegenerative disorder such as Parkinson disease.
Antioxidants/*pharmacology ; *Apoptosis ; Caspase 3/metabolism ; Cell Line, Tumor ; Cell Survival/drug effects ; Cytoprotection ; Dopamine/*physiology/toxicity ; Humans ; Membrane Potential, Mitochondrial/drug effects ; Poly(ADP-ribose) Polymerases/metabolism ; Proto-Oncogene Proteins c-bcl-2/metabolism ; Stilbenes/*pharmacology

OBJECTIVEThe selective loss of dopaminergic neurons in Parkinson's disease is suspected to correlate with the increase of cellular iron, which may be involved in the pathogenesis of PD by promotion of oxidative stress. This research investigated dopamine-induced oxidative stress toxicity contributed by iron and the production of dopamine-derived neurotoxins in dopaminergic SH-SY5Y cells.

METHODSAfter the SH-SY5Y cells were pre-incubated with dopamine and Fe2+ for 24 h, the cell viability, hydroxyl radical, melondialdehyde, cell apoptosis, and catechol isoquinolines were measured by lactate dehydrogenase assay, salicylic acid trapping method, thiobarbuteric acid assay, Hoechst 33258 staining and HPLC-electrochemical detection (HPLC-ECD), respectively.

RESULTS(1) Optimal dopamine (150 micromol/L) and Fe2+ (40 or 80 micromol/L) significantly increased the concentrations of hydroxy radicals and melondialdehyde in SH-SY5Y cells. (2) Induction with dopamine alone or dopamine and Fe2+ (dopamine/Fe2+) caused cell apoptosis. (3) Compared with untreated cells, the catechol isoquinolines, salsolinol and N-methyl-salsolinol in dopamine/Fe2+-induced cells were detected in increasing amounts.

CONCLUSIONDue to dopamine/Fe2+-induced oxidative stress similar to the state in the parkinsonian substantia nigra neurons, dopamine and Fe2+ impaired SH-SY5Y cells could be used as the cell oxidative stress model of Parkinson's disease. The catechol isoquinolines detected in cells may be involved in the pathogenesis of Parkinson's disease as potential neurotoxins.

Apoptosis ; drug effects ; physiology ; Catechols ; metabolism ; Cell Line, Tumor ; Cell Survival ; drug effects ; physiology ; Dopamine ; toxicity ; Dose-Response Relationship, Drug ; Humans ; Hydroxyl Radical ; metabolism ; Iron ; metabolism ; Iron Metabolism Disorders ; complications ; metabolism ; physiopathology ; Isoquinolines ; metabolism ; Malondialdehyde ; metabolism ; Models, Biological ; Nerve Degeneration ; chemically induced ; metabolism ; physiopathology ; Neurons ; drug effects ; metabolism ; Neurotoxins ; toxicity ; Oxidative Stress ; drug effects ; Parkinson Disease ; etiology ; metabolism ; physiopathology ; Salsoline Alkaloids ; metabolism ; Up-Regulation ; drug effects ; physiology

Previous studies have shown that electroacupuncture (EA) promotes recovery of motor function in Parkinson's disease (PD). However the mechanisms are not completely understood. Clinically, the subthalamic nucleus (STN) is a critical target for deep brain stimulation treatment of PD, and vesicular glutamate transporter 1 (VGluT1) plays an important role in the modulation of glutamate in the STN derived from the cortex. In this study, a 6-hydroxydopamine (6-OHDA)-lesioned rat model of PD was treated with 100 Hz EA for 4 weeks. Immunohistochemical analysis of tyrosine hydroxylase (TH) showed that EA treatment had no effect on TH expression in the ipsilateral striatum or substantia nigra pars compacta, though it alleviated several of the parkinsonian motor symptoms. Compared with the hemi-parkinsonian rats without EA treatment, the 100 Hz EA treatment significantly decreased apomorphine-induced rotation and increased the latency in the Rotarod test. Notably, the EA treatment reversed the 6-OHDA-induced down-regulation of VGluT1 in the STN. The results demonstrated that EA alleviated motor symptoms and up-regulated VGluT1 in the ipsilateral STN of hemi-parkinsonian rats, suggesting that up-regulation of VGluT1 in the STN may be related to the effects of EA on parkinsonian motor symptoms via restoration of function in the cortico-STN pathway.
Adrenergic Agents ; toxicity ; Animals ; Apomorphine ; pharmacology ; Disease Models, Animal ; Dopamine Agonists ; pharmacology ; Electroacupuncture ; methods ; Functional Laterality ; drug effects ; Male ; Medial Forebrain Bundle ; injuries ; Motor Activity ; drug effects ; physiology ; Neurons ; drug effects ; metabolism ; Oxidopamine ; toxicity ; Parkinson Disease, Secondary ; chemically induced ; physiopathology ; therapy ; Rats ; Rats, Sprague-Dawley ; Subthalamic Nucleus ; drug effects ; metabolism ; pathology ; Tyrosine 3-Monooxygenase ; metabolism ; Up-Regulation ; drug effects ; physiology ; Vesicular Glutamate Transport Protein 1 ; metabolism

OBJECTIVETo investigate the toxicity of copper on MES23.5 dopaminergic cells and the probable mechanisms involved in this process.

METHODSMES23.5 dopaminergic cells were selected as our experimental model. [3-(4, 5-dimethylthiazol-2-yl)-2, 5 diphenyltetrazolium bromide] (MTT) assay was used to detect the influence of copper on the cell viability. The semi-quantitative reverse transcription polymerase chain reaction (RT-PCR), Western blotting and the high performance liquid chromatography-electrochemical detection (HPLC-ECD) have been used to detect the tyrosine hydroxlase (TH) mRNA and protein expression and the dopamine content in MES23.5 cells. The flow cytometry have been used to detect the changes of mitochondrial transmembrane potential.

RESULTS100 and 200 mumol/L copper had no effect on the MES23.5 cell viability, whereas 400 and 800 mumol/L of copper could decrease the cell viability (P < 0.01). Treating cells with 200 mumol/L copper for 24 h decreased the TH mRNA expression, the TH expression and the dopamine content compared with the control (P < 0.01, P < 0.01, P < 0.05, respectively). Besides, the mitochondrial transmembrane potential also decreased with the treatment of 200 mumol/L copper for 24 h (P < 0.01).

CONCLUSIONCopper could exert the toxic effects on MES23.5 dopaminergic cells and decrease the cell function. The dysfunction of mitochondria may be the mechanism of this toxicity effect.

Animals ; Cell Survival ; drug effects ; genetics ; Cells, Cultured ; Copper ; metabolism ; toxicity ; Dopamine ; biosynthesis ; Dose-Response Relationship, Drug ; Hybridomas ; Membrane Potential, Mitochondrial ; drug effects ; genetics ; Mice ; Mitochondria ; drug effects ; metabolism ; pathology ; Nerve Degeneration ; chemically induced ; metabolism ; physiopathology ; Neurons ; drug effects ; metabolism ; pathology ; Neurotoxins ; toxicity ; Oxidative Stress ; drug effects ; physiology ; Parkinson Disease ; etiology ; metabolism ; physiopathology ; RNA, Messenger ; drug effects ; metabolism ; Rats ; Tyrosine 3-Monooxygenase ; drug effects ; genetics ; metabolism

OBJECTIVETo study the effects of intranigral injection of different doses of CuSO4.5H2O on dopaminergic neuron in the nigrostriatal system of rats.

METHODSWistar rats were divided into four groups, including control group, 10 nmol, 50 nmol and 200 nmol copper injected into left substantia nigra (SN) groups. Seven days after the intranigral injection of copper, dopamine (DA) contents in the striatum (Str) were measured by high performance lipid chromotophotography (HPLC); the density of tyrosine hydroxylase (TH) positive axons in the Str was measured by TH staining method; TH and Caspase-3 mRNA expression in the SN were measured by semi-quantitative RT-PCR. We detected the activity of superoxide dismutase (SOD) in the lesioned midbrain of rats using biochemical methods.

RESULTSDA and its metabolites contents had no significant difference between control group and low dose (10 nmol) copper group. But from 50 nmol copper group, DA contents in the lesioned sides were reduced with the increase in the copper doses injected, showing a significant linear correlation (F = 34.16, P < 0.01). In the 50 nmol copper group, TH positive axons in the Str decreased compared with those of the control and unlesioned sides (F = 121.9, P < 0.01). In the 50 nmol copper group, TH mRNA expression decreased (t = 3.12, P < 0.01) while Caspase-3 mRNA expression increased (t = 8.96, P < 0.01) in the SN compared with the control. SOD activity decreased in the midbrain of rats treated with 50 nmol copper compared with that of the control (t = 2.33, P < 0.01).

CONCLUSIONCopper could induce damage of dopaminergic neurons in the SN of rats through destroying antioxidant defenses and promoting apoptosis.

Animals ; Apoptosis ; drug effects ; physiology ; Axons ; drug effects ; metabolism ; pathology ; Caspase 3 ; drug effects ; genetics ; metabolism ; Copper ; toxicity ; Corpus Striatum ; drug effects ; metabolism ; pathology ; Dopamine ; metabolism ; Dose-Response Relationship, Drug ; Male ; Nerve Degeneration ; chemically induced ; metabolism ; pathology ; Neural Pathways ; drug effects ; metabolism ; pathology ; Neurons ; drug effects ; metabolism ; pathology ; Neurotoxins ; toxicity ; Oxidative Stress ; drug effects ; physiology ; Parkinsonian Disorders ; chemically induced ; metabolism ; physiopathology ; RNA, Messenger ; drug effects ; metabolism ; Rats ; Rats, Wistar ; Substantia Nigra ; drug effects ; metabolism ; pathology ; Superoxide Dismutase ; drug effects ; genetics ; metabolism ; Superoxide Dismutase-1 ; Tyrosine 3-Monooxygenase ; drug effects ; genetics ; metabolism ; Wallerian Degeneration ; chemically induced ; metabolism ; pathology

OBJECTIVETo evaluate the role of thrombin-activated microglia in the neurodegeneration of nigral dopaminergic neurons in the rat substantia nigra (SN) in vivo.

METHODSAfter stereotaxic thrombin injection into unilateral SN of rats, immunostaining, reverse transcription polymerase chain reaction (RT-PCR) and biochemical methods were used to observe tyrosine hydroxylase (TH) immunoreactive positive cells, microglia activation, nitric oxide (NO) amount and inducible nitric-oxide synthase (iNOS) expression.

RESULTS(1) Selective damage to dopaminergic neurons was produced after thrombin injection, which was evidenced by loss of TH immunostaining in time-dependent manner; (2) Strong microglial activation was observed in the SN; (3) RT-PCR demonstrated the early and transient expression of neurotoxic factors iNOS mRNA in the SN. Immunofluorescence results found that thrombin induced expression of iNOS in microglia. The NO production in the thrombin-injected rats was significantly higher than that of controls (P < 0.05).

CONCLUSIONThrombin intranigral injection can injure the dopaminergic neurons in the SN. Thrombin-induced microglia activation precedes dopaminergic neuron degeneration, which suggest that activation of microglia and release of NO may play important roles in dopaminergic neuronal death in the SN.

Animals ; Disease Progression ; Dopamine ; biosynthesis ; Encephalitis ; chemically induced ; metabolism ; physiopathology ; Female ; Gliosis ; chemically induced ; metabolism ; physiopathology ; Immunohistochemistry ; Inflammation Mediators ; toxicity ; Injections ; Microglia ; drug effects ; metabolism ; Nerve Degeneration ; chemically induced ; metabolism ; physiopathology ; Neurons ; drug effects ; metabolism ; pathology ; Nitric Oxide ; biosynthesis ; Nitric Oxide Synthase Type II ; drug effects ; metabolism ; Oxidative Stress ; drug effects ; physiology ; Parkinsonian Disorders ; chemically induced ; metabolism ; physiopathology ; RNA, Messenger ; drug effects ; metabolism ; Rats ; Rats, Sprague-Dawley ; Reverse Transcriptase Polymerase Chain Reaction ; Substantia Nigra ; drug effects ; metabolism ; physiopathology ; Thrombin ; toxicity ; Time Factors ; Tyrosine 3-Monooxygenase ; drug effects ; genetics ; metabolism ; Up-Regulation ; drug effects ; physiology

OBJECTIVENeuroinflammation with microglial activation has been implicated to have a strong association with the progressive dopaminergic neuronal loss in Parkinson's disease (PD). The present study was undertaken to evaluate the activation profile of microglia in 1-methyl-4-phenyl pyridinium (MPP+)-induced hemiparkinsonian rats. Triptolide, a potent immunosuppressant and microglia inhibitor, was then examined for its efficacy in protecting dopaminergic neurons from injury and ameliorating behavioral disabilities induced by MPP+.

METHODSThe rat model of PD was established by intranigral microinjection of MPP+. At baseline and on day 1, 3, 7, 14, 21 following MPP+ injection, the degree of microglial activation was examined by detecting the immunodensity of OX-42 (microglia marker) in the substantia nigra (SN). The number of viable dopaminergic neurons was determined by measuring tyrosine hydroxylase (TH) positive neurons in the SN. Behavioral performances were evaluated by counting the number of rotations induced by apomorphine, calculating scores of forelimb akinesia and vibrissae-elicited forelimb placing asymmetry.

RESULTSIntranigral injection of MPP+ resulted in robust activation of microglia, progressive depletion of dopaminergic neurons, and ongoing aggravation of behavioral disabilities in rats. Triptolide significantly inhibited microglial activation, partially prevented dopaminergic cells from death and improved behavioral performances.

CONCLUSIONThese data demonstrated for the first time a neuroprotective effect of triptolide on dopaminergic neurons in MPP+-induced hemiparkinsonian rats. The protective effect of triptolide may, at least partially, be related to the inhibition of MPP+-induced microglial activation. Our results lend strong support to the use of immunosuppressive agents in the management of PD.

1-Methyl-4-phenylpyridinium ; antagonists & inhibitors ; toxicity ; Animals ; Biomarkers ; metabolism ; CD11b Antigen ; analysis ; metabolism ; Cell Count ; Cell Survival ; drug effects ; physiology ; Disability Evaluation ; Diterpenes ; pharmacology ; therapeutic use ; Dopamine ; metabolism ; Encephalitis ; drug therapy ; immunology ; prevention & control ; Epoxy Compounds ; pharmacology ; therapeutic use ; Gliosis ; drug therapy ; immunology ; prevention & control ; Herbicides ; antagonists & inhibitors ; toxicity ; Immunosuppression ; methods ; Immunosuppressive Agents ; pharmacology ; therapeutic use ; Male ; Microglia ; drug effects ; immunology ; Neurons ; drug effects ; immunology ; pathology ; Parkinsonian Disorders ; drug therapy ; immunology ; physiopathology ; Phenanthrenes ; pharmacology ; therapeutic use ; Rats ; Rats, Sprague-Dawley ; Substantia Nigra ; drug effects ; immunology ; physiopathology ; Treatment Outcome ; Tyrosine 3-Monooxygenase ; analysis ; metabolism