Animals ; Astrocytes ; immunology ; metabolism ; Male ; Microglia ; immunology ; metabolism ; Neurons ; metabolism ; Oxidopamine ; metabolism ; Parkinson Disease ; immunology ; Rats ; Rats, Sprague-Dawley

The globus pallidus occupies a critical position in the indirect pathway of the basal ganglia circuit, which regulates movement under both normal and pathological conditions. Previous studies have shown that the globus pallidus receives dopaminergic innervation from the axonal collaterals of nigrostriatal fibers. Both dopamine Dand Dlike receptors are expressed in the globus pallidus. The present study was aimed to investigate the direct in vivo electrophysiological effects of dopamine Dlike receptors in the globus pallidus of both normal and parkinsonian rats. Extracellular recordings of multi-barreled microelectrode were used in the present study. In normal rats, micro-pressure ejection of dopamine Dlike receptor agonist quinpirole induced different effects on the firing rate of globus pallidus neurons. In 24 out of the 61 pallidal neurons, quinpirole significantly increased the firing rate by (62.7 ± 11.2)%. In another 16 neurons, quinpirole decreased the spontaneous firing rate by (37.5 ± 2.9)%. Furthermore, co-application of dopamine Dlike receptor antagonist, sulpride, blocked quinpirole-induced modulation of the firing rate of pallidal neurons. On the 6-hydroxydopamine (6-OHDA) lesioned side of parkinsonian rats, quinpirole increased the firing rate in 25 out of the 47 pallidal neurons by (64.2 ± 10.1)%, while decreased the firing rate in 11 neurons by (51.9 ± 6.2)%. Our findings suggest that activation of pallidal dopamine Dlike receptors may bidirectionally modulate the spontaneous firing of globus pallidus neurons in both normal and parkinsonian rats.
Animals ; Disease Models, Animal ; Dopamine ; Globus Pallidus ; metabolism ; Male ; Neurons ; Oxidopamine ; Parkinsonian Disorders ; metabolism ; Rats ; Receptors, Dopamine D1 ; metabolism ; Receptors, Dopamine D2 ; metabolism

L-dopa (l-3,4-dihydroxyphenylalanine)-induced dyskinesia (LID) is a debilitating complication of dopamine replacement therapy for Parkinson's disease. The potential contribution of striatal D₂ receptor (D₂R)-positive neurons and downstream circuits in the pathophysiology of LID remains unclear. In this study, we investigated the role of striatal D₂R⁺ neurons and downstream globus pallidus externa (GPe) neurons in a rat model of LID. Intrastriatal administration of raclopride, a D₂R antagonist, significantly inhibited dyskinetic behavior, while intrastriatal administration of pramipexole, a D₂-like receptor agonist, yielded aggravation of dyskinesia in LID rats. Fiber photometry revealed the overinhibition of striatal D₂R⁺ neurons and hyperactivity of downstream GPe neurons during the dyskinetic phase of LID rats. In contrast, the striatal D₂R⁺ neurons showed intermittent synchronized overactivity in the decay phase of dyskinesia. Consistent with the above findings, optogenetic activation of striatal D₂R⁺ neurons or their projections in the GPe was adequate to suppress most of the dyskinetic behaviors of LID rats. Our data demonstrate that the aberrant activity of striatal D₂R⁺ neurons and downstream GPe neurons is a decisive mechanism mediating dyskinetic symptoms in LID rats.
Rats ; Animals ; Levodopa/toxicity* ; Dopamine ; Parkinsonian Disorders/drug therapy* ; Oxidopamine ; Dyskinesia, Drug-Induced ; Corpus Striatum/metabolism* ; Neurons/metabolism* ; Receptors, Dopamine D2/metabolism* ; Antiparkinson Agents/toxicity*

The purpose of the present study is to observe the effect of electro-acupuncture (EA) stimulation on intracerebral neurotransmitters in a rat model of Parkinson's disease (PD), and explore the possible mechanism. We used 6-hydroxydopamine (6-OHDA) injection in medial forebrain bundle (MFB) in the right brain of Sprague Dawley (SD) rat to establish the parkinsonian rat model, and randomly divided the PD rats into model and 100 Hz EA stimulation groups (n =10 in each group). EA stimulation group received 4 courses of EA stimulation on Baihui (GV-20) and Dazhui (GV-14) acupuncture points. Moreover, ten rats were randomly selected as sham operation group, only receiving normal saline (NS) injection in MFB. Then apomorphine (APO)-induced rotational behavior in different groups was recorded, and the contents of γ-aminobutyric acid (GABA) in the brain were analyzed with high pressure/performance liquid chromatography-electrochemical detection (HPLC-ECD). The results showed that model group exhibited abnormal rotational behavior with APO treatment, suggesting the successful establishment of PD model. Compared with sham operation group, model group showed increased GABA contents in cortex and striatum, as well as decreased GABA content in ventral midbrain, on the lesioned side. EA stimulation could effectively ameliorate the abnormal rotational behavior of PD rat. Compared with the model group, EA stimulation decreased the ratio of GABA content on the lesioned side to that on unlesioned side in the cortex, while increased the ratios in the striatum and cerebellum. However, there was no difference of the ratio in the ventral midbrain among three groups. These results suggest high-frequency EA stimulation significantly improves the abnormal behavior of PD rats, which may exert through enhancing the inhibitory effect of cerebellum-basal ganglia-cortical loop on motor center.
Acupuncture Therapy ; Animals ; Brain ; metabolism ; Electroacupuncture ; Male ; Motor Cortex ; physiology ; Oxidopamine ; Parkinson Disease, Secondary ; chemically induced ; metabolism ; therapy ; Rats ; Rats, Sprague-Dawley ; gamma-Aminobutyric Acid ; metabolism

OBJECTIVE: To explore whether the using of mimetic peptide Gap27, a selective inhibitor of connexin 43 (Cx43), could block the death of dopamine neurons and influence the expression of Cx43 in 6-hydroxydopamine (6-OHDA)-induced Parkinson's disease mouse models. METHODS: Eighteen C57BL/6 mice were randomly divided into control group, 6-OHDA group and 6-OHDA+Gap27 group, with 6 mice in each group. Bilateral substantia nigra stereotactic injection was performed. The control group was injected with ascorbate solution, 6-OHDA group was injected with 6-OHDA solution, and 6-OHDA+Gap27 group was injected with 6-OHDA and Gap27 mixed solution. Immuno-histochemical staining was used to detect the number of dopamine neurons, quantitative real-time polymerase chain reaction (qRT-PCR) was used to detect the expression of Cx43 messenger ribonucleic acid (mRNA), immuno-fluorescence staining was used to detect the distribution of Cx43 protein, the contents of Cx43 protein and Cx43 phosphorylation at serine 368 (Cx43-ps368) in mouse midbrain were detected by Western blot. RESULTS: After injection of 6-OHDA, numerous dopamine neurons in substantia nigra died as Cx43 content increased, Cx43-ps368 content decreased. Mixing Gap27 while injecting 6-OHDA could reduce the number of death dopamine neurons and weaken the changes of Cx43 and Cx43-ps368 content caused by 6-OHDA. The number of tyrosine hydroxylase (TH) immunoreactive positive neurons in 6-OHDA group decreased to 27.7% ± 0.02% of the control group (P < 0.01); The number of TH immunoreactive positive neurons in 6-OHDA+Gap27 group was (1.64±0.16) times higher than that in 6-OHDA group (P < 0.05); The content of total Cx43 protein in 6-OHDA group was (1.44±0.07) times higher than that in 6-OHDA+Gap27 group (P < 0.05) while (1.68±0.07) times higher than that in control group (P < 0.01). In 6-OHDA group, the content of Cx43-ps368 protein and its proportion in total Cx43 protein were significantly lower than that in 6-OHDA+Gap27 group (P < 0.05). CONCLUSION In 6-OHDA mouse models, mimetic peptide Gap27 played a protective role in reducing the damage to substantia nigra dopamine neurons, which was induced by 6-OHDA. The overexpression of Cx43 protein might have neurotoxicity to dopamine neuron. Meanwhile, decreasing Cx43 protein level and keeping Cx43-ps368 protein level may be the protective mechanisms of Gap27.
Animals ; Connexin 43/pharmacology* ; Disease Models, Animal ; Dopaminergic Neurons/metabolism* ; Mice ; Mice, Inbred C57BL ; Oxidopamine/metabolism* ; Parkinson Disease/metabolism* ; Peptides/pharmacology* ; Tyrosine 3-Monooxygenase/pharmacology*

OBJECTIVETo investigate the effect and mechanism of prepared Radix Polygoni Multiflori (RPM) on the elevation of extracellular hydroxyl radical in striatum of rats induced by intracerebral perfusion of 6-hydroxy dopamine (6-OHDA).

METHODSCerebral microdialysis was used to establish the model. Hydroxyl radical was captured by salicylic acid, and 2,3-dihydroxy benzyl acid (2,3-DHBA) and 2,5-dihydroxy benzyl acid (2,5-DHBA) formed by hydroxyl radical in vital brain were measured by high performance liquid chromatography-electrochemical detector (HPLC-ED).

RESULTSAfter perfusion of 6-OHDA in brain of rats, the levels of 2,3-DHBA and 2,5-DHBA in the model group increased rapidly. The former was higher during the whole course of observation (P<0.01), while the latter was higher at most time points than that in the control group (P<0.05 or P<0.01). The level of 2,3-DHBA in the RPM group was lower than that in the model group at 5 time points (P < 0.05, P < 0. 01).

CONCLUSIONRPM could inhibit the elevating of extracellular hydroxyl radical in striatum of rats induced by intracerebral perfusion of 6-OHDA, indicating one of the brain protective mechanisms of RPM may be related to its anti-oxidation effect.

Animals ; Corpus Striatum ; drug effects ; metabolism ; Drugs, Chinese Herbal ; pharmacology ; Hydroxyl Radical ; metabolism ; Male ; Microdialysis ; Neuroprotective Agents ; pharmacology ; Oxidopamine ; Polygonum ; chemistry ; Random Allocation ; Rats ; Rats, Sprague-Dawley

This study was undertaken to observe the biochemical changes in striatum of Parkinson's disease (PD) rat model by modified proton magnetic resonance spectroscopy. 12 SD rats were divided into model (n=7) and control (n=5) groups. At 3 weeks after the injection of 6-hydroxydopamine into right striatum, 1H-MRS on the striatum was taken by modified proton magnetic resonance spectroscopy, and then tyrosine hydroxylase (TH) immunostatining was used to visualize the changes of the neurons in substantia nigra and neurites in striatum. The results showed that TH positive neurons and neurites in the substantia nigra compacts (SNc) and striatum in the normal side of the rat model of PD were decreased (P < 0.05), which proved the successful establishment of PD models. The NAA/Cr ratio of the injected side striatum of model group was lower than that of the normal side (P < 0.05). The ratios of Cho/Cr showed no significant difference between the two sides (P > 0.05). These results indicated that the modified 1.5T 1H-MRS should be a noninvasive technique which could provide useful information about the biochemical metabolites in striatum for the study of PD in rat model.
Animals ; Corpus Striatum ; enzymology ; Female ; Magnetic Resonance Spectroscopy ; methods ; Male ; Oxidopamine ; Parkinson Disease, Secondary ; chemically induced ; metabolism ; Rats ; Rats, Sprague-Dawley ; Tyrosine 3-Monooxygenase ; metabolism

OBJECTIVETo investigate the activity of pyramidal neurons in the medial prefrontal cortex (mPFC) of normal and 6-OHDA-lesioned rats and the responses of the neurons to 5-hydroxytryptamine-7 (5-HT(7)) receptor stimulation.

METHODSThe changes in spontaneous firing of the pyramidal neurons in the mPFC in response to 5-HT(7) receptor stimulation were observed by extracellular recording in normal and 6-OHDA-lesioned rats.

RESULTSBoth systemic and local administration of 5-HT(7) receptor agonist AS 19 resulted in 3 response patterns (excitation, inhibition and no change) of the pyramidal neurons in the mPFC of normal and 6-OHDA-lesioned rats. In normal rats, the predominant response of the pyramidal neurons to AS 19 stimulation was excitatory, and the inhibitory effect of systemically administered AS 19 was reversed by GABAA receptor antagonist picrotoxinin. In the lesioned rats, systemic administration of AS 19 also increased the mean firing rate of the pyramidal neurons, but the cumulative dose for producing excitation was higher than that in normal rats. Systemic administration of AS 19 produced an inhibitory effect in the lesioned rats, which was partially reversed by picrotoxinin. Local administration of AS 19 at the same dose did not change the ?ring rate of the neurons in the lesioned rats.

CONCLUSIONThe activity of mPFC pyramidal neurons is directly or indirectly regulated by 5-HT7 receptor, and degeneration of the nigrostriatal pathway leads to decreased response of these neurons to AS 19.

Action Potentials ; Animals ; Oxidopamine ; Parkinson Disease ; metabolism ; Prefrontal Cortex ; cytology ; Pyramidal Cells ; drug effects ; Rats ; Receptors, Serotonin ; metabolism ; Serotonin Receptor Agonists ; pharmacology

Parkinson's disease is known to exhibit progressive degeneration of the dopaminergic neurons in the substantia nigra via inhibition of glutathione metabolism. It is well known that 6-Hydroxydopamine (6-OHDA) induces Parkinson's disease-like symptoms, while resveratrol (3,5,4'-trihydroxystilbene) has been shown to have anti-inflammatory and antioxidant effects. In the present study, we investigated the neuroprotective effects of resveratrol, a phytoalexin found in grapes and various plants, on 6-OHDA-induced cell damage to the SH-SY5Y human neuroblastoma cell line. Resveratrol (5 and 10 microM) inhibited 6-OHDA (60 microM)-induced cytotoxicity in SH-SY5Y cells and induced a reduction of the number of apoptotic nuclei caused by 6-OHDA treatment. Additionally, the total apoptotic rate of cells treated with both resveratrol (10 microM) and 6-OHDA (60 microM) was less than that of 6-OHDA treated cells. Resveratrol also dose-dependently (1, 5 and 10 microM) scavenged reactive oxygen species (ROS) induced by 6-OHDA in SH-SY5Y cells and prevented depletion of glutathione in response to the 6-OHDA-induced cytotoxicity in the glutathione assay. Overall, these results indicate that resveratrol exerts a neuroprotective effect against 6-OHDA-induced cytotoxicity of SH-SY5Y cells by scavenging ROS and preserving glutathione.
Antioxidants ; Apoptosis ; Cell Line* ; Dopaminergic Neurons ; Glutathione ; Humans ; Metabolism ; Neuroblastoma ; Neuroprotective Agents* ; Oxidopamine ; Parkinson Disease ; Reactive Oxygen Species ; Substantia Nigra ; Vitis

OBJECTIVETo investigate the changes in the firing activity of noradrenergic neurons in the locus coeruleus (LC) in a rat model of Parkinson disease (PD).

METHODS2 and 4 weeks after unilateral lesion of the nigrostriatal pathway in the rat by local injection of 6-hydroxydopamine (6-OHDA) into the right substantia nigra pars compacta (SNc), the firing activity of noradrenergic neurons in LC was recorded by extracellular single unit recording.

RESULTSThe firing rate of LC noradrenergic neurons increased significantly 2 and 4 weeks after 6-OHDA lesions compared to normal rats, respectively (P < 0.05). The percentage of irregularly firing neurons was obviously higher than that of normal rats during the fourth week after SNc lesion (P < 0.05).

CONCLUSIONLC noradrenergic neurons are overactive and more irregular in 6-OHDA-lesioned rats. These changes suggest an implication of the LC in the pathophysiological mechanism of PD.

Action Potentials ; physiology ; Animals ; Disease Models, Animal ; Locus Coeruleus ; pathology ; Male ; Neurons ; physiology ; Norepinephrine ; metabolism ; Oxidopamine ; Parkinsonian Disorders ; chemically induced ; pathology ; Rats ; Rats, Sprague-Dawley ; Time Factors