The ventral anterior (VA) nucleus of the thalamus is a major target of the basal ganglia and is closely associated with the pathogenesis of Parkinson's disease (PD). Notably, the VA receives direct innervation from the hypothalamic histaminergic system. However, its role in PD remains unknown. Here, we assessed the contribution of histamine to VA neuronal activity and PD motor deficits. Functional magnetic resonance imaging showed reduced VA activity in PD patients. Optogenetic activation of VA neurons or histaminergic afferents significantly alleviated motor deficits in 6-OHDA-induced PD rats. Furthermore, histamine excited VA neurons via H1 and H2 receptors and their coupled hyperpolarization-activated cyclic nucleotide-gated channels, inward-rectifier K⁺ channels, or Ca²⁺-activated K⁺ channels. These results demonstrate that histaminergic afferents actively compensate for Parkinsonian motor deficits by biasing VA activity. These findings suggest that targeting VA histamine receptors and downstream ion channels may be a potential therapeutic strategy for PD motor dysfunction.
Animals ; Histamine/metabolism* ; Male ; Oxidopamine/toxicity* ; Rats ; Ventral Thalamic Nuclei/physiopathology* ; Rats, Sprague-Dawley ; Disease Models, Animal ; Parkinson Disease/metabolism* ; Neurons/physiology* ; Humans ; Optogenetics

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*

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*

The traditionally used oriental herbal medicine Moutan Cortex Radicis [MCR; Paeonia Suffruticosa Andrews (Paeoniaceae)] exerts anti-inflammatory, anti-spasmodic, and analgesic effects. In the present study, we investigated the therapeutic effects of differently fractioned MCR extracts in a 6-hydroxydopamine (OHDA)-induced Parkinson's disease model and neuro-blastoma B65 cells. Ethanol-extracted MCR was fractionated by n-hexane, butanol, and distilled water. Adult Sprague-Dawley rats were treated first with 20 μg of 6-OHDA, followed by three MCR extract fractions (100 or 200 mg·kg) for 14 consecutive days. In the behavioral rotation experiment, the MCR extract-treated groups showed significantly decreased number of net turns compared with the 6-OHDA control group. The three fractions also significantly inhibited the reduction in tyrosine hydroxylase-positive cells in the substantia nigra pars compacta following 6-OHDA neurotoxicity. Western blotting analysis revealed significantly reduced tyrosine hydroxylase expression in the substantia nigra pars compacta in the 6-OHDA-treated group, which was significantly inhibited by the n-hexane or distilled water fractions of MCR. B65 cells were exposed to the extract fractions for 24 h prior to addition of 6-OHDA for 30 min; treatment with n-hexane or distilled water fractions of MCR reduced apoptotic cell death induced by 6-OHDA neurotoxicity and inhibited nitric oxide production and neuronal nitric oxide synthase expression. These results showed that n-hexane- and distilled water-fractioned MCR extracts inhibited 6-OHDA-induced neurotoxicity by suppressing nitric oxide production and neuronal nitric oxide synthase activity, suggesting that MCR extracts could serve as a novel candidate treatment for the patients with Parkinson's disease.
Animals ; Anti-Inflammatory Agents ; pharmacology ; therapeutic use ; Antiparkinson Agents ; pharmacology ; therapeutic use ; Cell Death ; drug effects ; Cell Line ; Disease Models, Animal ; Drugs, Chinese Herbal ; chemistry ; Neurons ; pathology ; Nitric Oxide ; analysis ; Nitric Oxide Synthase Type I ; biosynthesis ; Oxidopamine ; toxicity ; Paeonia ; chemistry ; Parkinsonian Disorders ; chemically induced ; drug therapy ; Phytotherapy ; Plant Extracts ; pharmacology ; therapeutic use ; Plants, Medicinal ; Rats ; Rats, Sprague-Dawley ; Substantia Nigra ; drug effects ; enzymology ; Tyrosine 3-Monooxygenase ; genetics ; metabolism

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 observe the preventive effect of different compatibilities of Ramulus Cinnamomi (RC) and Radix Paeomiae alba (RPA) in Guizhi Decoction (GZD) on neurotransmitters and their rate-limiting enzymes, and neurotrophic factors of cardiac sympathetic denervation model rats induced by 6-hydroxydopamine (6-OHDA).

METHODSTotally 54 male Wistar rats were randomly divided into 6 groups, i.e., the blank control group, the model group, the methycobal group, the 2:1 (RC/RPA) Guishao group, the 1:2 Guishao group, and the 1:1 Guishao group, 9 in each group. Sympathetic denervation was induced by intraperitoneal injection of 6-OHDA for three successive days. Rats in the methycobal group and GZD groups were administered with corresponding decoction by gastrogavage 1 week before modeling (methycobal at the daily dose 0.15 mg/kg; GZD at the daily dose of 4.0, 5.5, 5.5 g crude drugs/kg for GZD 1:1, 1:2, and 2:1 groups). All medication lasted for 10 successive days. Levels of norepinephrine (NE), tyrosine hydroxylase (TH), choline acetyl-transferase (ChAT), nerve growth factor (NGF), growth associated protein43 (GAP-43) and ciliary neurotrophic factor (CNTF) in myocar- dial homogenates of right atrium and ventricular septum were detected by ELISA.

RESULTSCompared with the blank control group, levels of NE, TH, TH/ChAT ratio, and GAP-43 in myocardial homogenates of right atrium and ventricular septum decreased in the model group, and level of NGF increased (P < 0.01, P < 0.05). Compared with the model group, levels of NE and GAP-43 increased in the right atrium and interventricular septum; NGF level of the ventricular septum decreased in the methycobal group and each GZD groups. TH and TH/ChAT ratio in the right atrium increased in the 2:1 Guishao group and the 1:2 Guishao group (P < 0.01, P < 0.05); NGF levels in the right atrium and interventricular septum decreased only in the 1:1 Guishao group (P < 0.01, P< 0.05). Compared with the methycobal group, levels of NE, TH, and GAP-43 in the right atrium and interventricular septum increased, and NGF levels in the right atrium and interventricular septum decreased in the 1:1 Guishao group (P < 0.05). Compared with the methycobal group, levels of NE and GAP-43 in interventricular septum increased in the 2:1 Guishao group (P < 0.05).

CONCLUSIONGZD (with the proportion between RC and RPA 2:1 and 1:1) could improve contents of neurotransmitters and their rate-limiting enzymes, as well as neurotrophic factors in cardiac sympathetic denervation model rats induced by 6-OHDA, alleviate cardiac sympathetic denervation induced by 6-OHDA, and maintain the balance of sympathetic-vagal nerve system.

Animals ; Choline O-Acetyltransferase ; metabolism ; Ciliary Neurotrophic Factor ; metabolism ; Drugs, Chinese Herbal ; pharmacology ; GAP-43 Protein ; metabolism ; Heart ; drug effects ; innervation ; Male ; Myocardium ; metabolism ; Nerve Growth Factor ; metabolism ; Norepinephrine ; metabolism ; Oxidopamine ; adverse effects ; Random Allocation ; Rats ; Rats, Wistar ; Sympathectomy ; Tyrosine 3-Monooxygenase ; metabolism

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

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

Mutations or inactivation of parkin, an E3 ubiquitin ligase, are associated with familial form or sporadic Parkinson's disease (PD), respectively, which manifested with the selective vulnerability of neuronal cells in substantia nigra (SN) and striatum (STR) regions. However, the underlying molecular mechanism linking parkin with the etiology of PD remains elusive. Here we report that p62, a critical regulator for protein quality control, inclusion body formation, selective autophagy and diverse signaling pathways, is a new substrate of parkin. P62 levels were increased in the SN and STR regions, but not in other brain regions in parkin knockout mice. Parkin directly interacts with and ubiquitinates p62 at the K13 to promote proteasomal degradation of p62 even in the absence of ATG5. Pathogenic mutations, knockdown of parkin or mutation of p62 at K13 prevented the degradation of p62. We further showed that parkin deficiency mice have pronounced loss of tyrosine hydroxylase positive neurons and have worse performance in motor test when treated with 6-hydroxydopamine hydrochloride in aged mice. These results suggest that, in addition to their critical role in regulating autophagy, p62 are subjected to parkin mediated proteasomal degradation and implicate that the dysregulation of parkin/p62 axis may involve in the selective vulnerability of neuronal cells during the onset of PD pathogenesis.
Adaptor Proteins, Signal Transducing ; chemistry ; metabolism ; Animals ; HEK293 Cells ; Heat-Shock Proteins ; chemistry ; metabolism ; Humans ; Lysine ; metabolism ; Mice ; Neurons ; metabolism ; pathology ; Oxidopamine ; pharmacology ; Parkinson Disease ; metabolism ; pathology ; Proteasome Endopeptidase Complex ; metabolism ; Protein Stability ; Proteolysis ; drug effects ; Sequestosome-1 Protein ; Ubiquitin-Protein Ligases ; metabolism ; Ubiquitination ; drug effects

OBJECTIVETo explore the alterations of apoptosis factor Bcl-2/Bax in the early Parkinson's disease (PD) rats and the protective effect of scorpion venom derived bioactive peptide.

METHODSHealthy male SD rats (180-220 g) were randomly divided into 4 groups (n = 10): early PD model group, sham operation group, scorpion venom derived bioactive peptide control group, scorpion venom derived bioactive peptide therapy group. 6-hydroxydopamine (6-OHDA) was used to prepare the early PD rat model. The immunohistochemistry was used to detect the expression of Bax and Bcl-2 and further explore the mechanism of anti-apoptosis regarding the neuroprotective effect of scorpion venom derived bioactive peptide.

RESULTSThe results indicated that compared with the control rats, the immunostaining of Bax in the brain increased significantly while that of Bcl-2 decreased significantly in the lesion side of 6-OHDA treated rats. Interestingly, scorpion venom derived bioactive peptide could attenuate the above abnormal changes.

CONCLUSIONUp-regulation of Bax and down-regulation of Bcl-2 could participate in the early stage of PD and the anti-apoptotic mechanism could be involved in the neuroprotective effect exerted by scorpion venom derived activity peptide regarding the dopaminergic neuron in the early stage.

Animals ; Apoptosis ; Disease Models, Animal ; Down-Regulation ; Male ; Neuroprotective Agents ; chemistry ; Oxidopamine ; Parkinson Disease ; metabolism ; Peptides ; chemistry ; Proto-Oncogene Proteins c-bcl-2 ; metabolism ; Rats ; Rats, Sprague-Dawley ; Scorpion Venoms ; chemistry ; Up-Regulation ; bcl-2-Associated X Protein ; metabolism