Protein O-GlcNAcylation is a post-translational modification that links environmental stimuli with changes in intracellular signal pathways, and its disturbance has been found in neurodegenerative diseases and metabolic disorders. However, its role in the mesolimbic dopamine (DA) system, especially in the ventral tegmental area (VTA), needs to be elucidated. Here, we found that injection of Thiamet G, an O-GlcNAcase (OGA) inhibitor, in the VTA and nucleus accumbens (NAc) of mice, facilitated neuronal O-GlcNAcylation and decreased the operant response to sucrose as well as the latency to fall in rotarod test. Mice with DAergic neuron-specific knockout of O-GlcNAc transferase (OGT) displayed severe metabolic abnormalities and died within 4-8 weeks after birth. Furthermore, mice specifically overexpressing OGT in DAergic neurons in the VTA had learning defects in the operant response to sucrose, and impaired motor learning in the rotarod test. Instead, overexpression of OGT in GABAergic neurons in the VTA had no effect on these behaviors. These results suggest that protein O-GlcNAcylation of DAergic neurons in the VTA plays an important role in regulating the response to natural reward and motor learning in mice.
Animals ; Dopaminergic Neurons/physiology* ; GABAergic Neurons/physiology* ; Mice ; Nucleus Accumbens/metabolism* ; Reward ; Ventral Tegmental Area/metabolism*

Dopaminergic neurons in the ventral tegmental area (VTA) play an important role in cognition, emergence from anesthesia, reward, and aversion, and their projection to the cortex is a crucial part of the "bottom-up" ascending activating system. The prelimbic cortex (PrL) is one of the important projection regions of the VTA. However, the roles of dopaminergic neurons in the VTA and the VTA^DA-PrL pathway under sevoflurane anesthesia in rats remain unclear. In this study, we found that intraperitoneal injection and local microinjection of a dopamine D1 receptor agonist (Chloro-APB) into the PrL had an emergence-promoting effect on sevoflurane anesthesia in rats, while injection of a dopamine D1 receptor antagonist (SCH23390) deepened anesthesia. The results of chemogenetics combined with microinjection and optogenetics showed that activating the VTA^DA-PrL pathway prolonged the induction time and shortened the emergence time of anesthesia. These results demonstrate that the dopaminergic system in the VTA has an emergence-promoting effect and that the bottom-up VTA^DA-PrL pathway facilitates emergence from sevoflurane anesthesia.
Anesthesia ; Animals ; Dopaminergic Neurons/metabolism* ; Rats ; Receptors, Dopamine D1/metabolism* ; Sevoflurane/pharmacology* ; Ventral Tegmental Area/metabolism*

The accumulation of pathological α-synuclein (α-syn) in the central nervous system and the progressive loss of dopaminergic neurons in the substantia nigra pars compacta are the neuropathological features of Parkinson's disease (PD). Recently, the findings of prion-like transmission of α-syn pathology have expanded our understanding of the region-specific distribution of α-syn in PD patients. Accumulating evidence suggests that α-syn aggregates are released from neurons and endocytosed by glial cells, which contributes to the clearance of α-syn. However, the activation of glial cells by α-syn species produces pro-inflammatory factors that decrease the uptake of α-syn aggregates by glial cells and promote the transmission of α-syn between neurons, which promotes the spread of α-syn pathology. In this article, we provide an overview of current knowledge on the role of glia and α-syn pathology in PD pathogenesis, highlighting the relationships between glial responses and the spread of α-syn pathology.
Humans ; Parkinson Disease/pathology* ; alpha-Synuclein/metabolism* ; Dopaminergic Neurons/metabolism* ; Pars Compacta/metabolism*

Animals ; Dopamine ; metabolism ; Dopaminergic Neurons ; metabolism ; Humans ; Iron ; metabolism ; Oxidative Stress ; Parkinson Disease ; metabolism ; Pars Compacta ; metabolism ; alpha-Synuclein ; metabolism

Parkinson's disease (PD), one of the most frequent neurodegenerative disorders, is characterized by the selective loss of dopaminergic neurons in the substantia nigra (SN). Genetic vulnerability, aging, environmental insults are believed to contribute to the pathogenesis of PD. However, the cellular and molecular mechanism of dopaminergic neurons degeneration remains incompletely understood. Dopamine (DA) metabolism is a cardinal physiological process in dopaminergic neurons, which is closely related to the loss of dopaminergic neurons in the SN. DA metabolism takes part in several pathological processes of PD neurodegeneration, such as iron metabolism disturbance, α-synuclein mis-folding, endoplasmic reticulum stress, protein degradation dysfunction, neuroinflammatory response, etc. In this review, we will describe altered DA metabolism and its contributions to PD pathogenesis.
Dopamine ; Dopaminergic Neurons ; Humans ; Parkinson Disease/etiology* ; Substantia Nigra ; alpha-Synuclein/metabolism*

OBJECTIVE: To investigate the effect of curcumin on dopamine neurons in Parkinson's disease (PD) and its mechanism. METHODS: SH-SY5Y human neuroblastoma cells were treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to establish the PD cell model. The model cells were treated with curcumin and/or autophagy inhibitor 3-MA. After 48 h of drug treatment, the number of surviving dopamine neurons was detected by tyrosine hydroxylase immunofluorescence method. Western blotting was used to detect protein expression of α-Synuclein (α-Syn), transcription factor EB (TFEB) and autophagy-related proteins lysosome-associated membrane protein 2A (LAMP2A) and microtubule-associated protein 1 light chain 3-Ⅱ(LC3-Ⅱ); RT-PCR was used to detect mRNA expression of α-Syn. RESULTS: Compared with MPTP model group, curcumin increased the number of surviving dopamine neurons(<0.01), decreased both protein expression and mRNA expression of α-Syn (all <0.01), and increased protein expression of TFEB, LAMP2A and LC3-Ⅱ (all <0.01). When curcumin and 3-MA were given concurrently, the number of surviving dopamine neurons, protein expression of TFEB, LAMP2A and LC3-Ⅱ increased (<0.05 or <0.01), and both protein expression and mRNA expression of α-Syn decreased (<0.05 or <0.01) compared with MPTP model group; but the number of surviving dopamine neurons and protein expression of LAMP2A and LC3-Ⅱ decreased compared with curcumin group (all <0.05). CONCLUSIONS Curcumin exerts protective effect on dopamine neurons in PD, which may be associated with enhancing autophagy and promoting the clearance of α-Syn.
Animals ; Cell Line ; Curcumin ; pharmacology ; Dopaminergic Neurons ; drug effects ; Humans ; Mice ; Mice, Inbred C57BL ; Parkinson Disease ; alpha-Synuclein ; metabolism

Object of this study was to to evaluate the laterality of local cerebral cellular metabolism in various locations of the brain related to the symptomatic side of patients with clinically diagnosed idiopathic Parkinson's disease (IPD) and to verify GABA-related pathophysiology in IPD by comparing postoperative changes in (GABA+Glutamate)/Cr ratio from patients with IPD after stereotactic pallidotomy and thalamotomy. Fourteen patients with IPD(10 males and 4 females: age range 39-67 years) participated in the study. The patients were classified into two disease subgroups, one for tremor dominant group(n=7, T group), and the other bradykinesia and rigidity dominant one(n=7, B&R group). For T group, stereotactic VL(Vop, Vim) thalamotomy and subthalamotomy was performed and for the B&R group, stereotactic posteroventrolateral pallidotomy was selected. In Vivo 1H MRS study was performed on a 1.5 T MRI/MRS system(GE Sigma Advantage, version 4.8) using STEAM sequence after water suppression with CHESS RF pulse and dephasing gradients. After peak areas of creatine/phosphocreatine(Cr), choline-containning compound(Cho), N-Acetyl Aspartate(NAA), r-aminobutyric acid, (GABA) and glutamate(Glu) were calculated and processed, the metabolic ratios of NAA/Cr, Cho/Cr, and (GABA+Glu)/Cr in three different locations were calculated and compared with clinical symptoms and its changes after surgery. For the neuronal laterality in patients with IPD, there was significant differences of NAA/Cr ratio between the right and left sides of substantia nigra, thalamus and pallidum(p=0.00170). The magnitude of difference in NAA/Cr ratios between right and left side were significantly larger in substantia nigra(p=0.0141). Compared to the normal control values(1.82+/-0.52 in ages 27-50, 1.71+/-0.54 in ages 51-70 years), the neuronal loss was generally observed in at least one of three locationsin all patients. Moreover, NAA/Cr ratio was substantially lower in ipsilateral than contralateral substantia nigra of the parkinsonian symptomatic side. For preoperative(GABA+Glu)/Cr ratios of thalamus contralateral to the symptomatic side compared to that of ipsilateral, it was significant larger in thalamus of B&R group and significant smaller in T group. In the pallidotomy group, there was significant increase in the operated pallidum, whereas significant decrease in (GABA+Glu)/Cr ratios were noted in the operated side thalamus. And in the thalamotomy group, there were significant increase in the operated thalamus, whereas in the operated side pallidum, significant decrease in (GABA+Glu)/Cr ratios were noted. Neuronal laterality, pallidal neuronal loss and postoperative changes in GABA activity in patients with IPD were demonstrated on the basis of NAA/Cr and (GABA+Glu)/Cr ratio by In Vivo 1H MRS. The neuronal laterality was detected in the substantia nigra of all the parkinsonian patient, and NAA/Cr ratios in unilateral and bilateral disease were consistently lower in ipsilateral than in contralateral substantia nigra of the Parkinsonian disease side. Our result suggests that there may be another ongoing pathological process of ipsilateral neuronal degeneration with contralateral dopaminergic neuronal loss. The result of neuronal loss in pallidum supports with the previous reports concerning striatal degeneration in IPD. Our results concerning postoperative changes of (GABA+Glu)/Cr ratio suggests that separate pathophysiologic mechanisms may be involved in the development of two dominant symptom groups of IPD. That is, for the B&R group, pallidal overinhibition to the thalamus by the GABA-ergic system as previously noted, but for T group, a process other than GABA inhibitory mechanism with or without it may be involved.
Brain ; Dopaminergic Neurons ; Female ; gamma-Aminobutyric Acid ; Humans ; Hypokinesia ; Male ; Metabolism ; Neurons* ; Pallidotomy ; Parkinson Disease ; Steam ; Substantia Nigra ; Thalamus ; Tremor ; Water

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*

Animals ; Behavior, Animal ; physiology ; Dopamine ; metabolism ; Dopaminergic Neurons ; physiology ; Humans ; Mice ; Motor Activity ; physiology ; Parkinson Disease ; metabolism ; physiopathology ; Pars Compacta ; physiopathology

Objective: To observe the dynamic changes of brainstem locus coeruleus (LC) damage in Parkinson' s disease (PD) -like mice by paraquat (PQ) . Methods: In October 2019, 36 male C57BL/6 mice were randomly divided into the exposure group and the control group, with 18 mice in each group. The mice in the exposure group were given intraperitoneal injection of 15 mg/kg PQ, and the mice in the control group were given intraperitoneal injection of 0.9% saline, twice a week for 8 weeks. Neurobehavioral changes (pole climbing test, swimming test, open field test, tail hanging test, high plus maze test and water maze test) were observed at 4 weeks, 6 weeks and 8 weeks, respectively, and the changes of motor ability, emotion and cognitive function were evaluated. The brain tissue of mice were taken and stained with Hematoxylin-Eosin (HE) to observe the pathological changes of LC. Nissl staining was used to detect the changes of neuronal Nissl bodies in LC. Immunohistochemistry (IHC) staining was used to detect the expression of neuron nuclear antigen (NeuN) , dopamine (DA) neurons and norepinephrine (NE) neuron markers tyrosine hydroxylase (TH) , α-synuclein (α-syn) in substantia nigra (SN) and LC. The expression levels of NeuN, TH and α-syn in the midbrain and brainstem were detected by Western blotting. TUNEL staining was used to detect neuronal apoptosis in LC. Results: Compared with the 4th week of PQ exposure group, the time of pole climbing and swimming immobility were gradually increased, the ratio of open arm residence time of high plus maze test and the number of times of the platform and the residence time of platform quadrant in water maze test were gradually decreased (P<0.05) in the exposure group with the progress of exposure time. The results of HE and Nissl staining showed that the neurons in LC gradually arranged loosely, the nucleus were deeply stained, the cytoplasm was pyknosis, and the number of Nissl bodies gradually decreased (P<0.05) in the exposure group with the progress of exposure time. IHC results showed that the number of NeuN and TH positive cells in SN and LC of mice were gradually decreased, and the positive expression of α-syn was gradually increased (P<0.05) in the exposure group with the progress of exposure time. Western blotting results showed that the expression levels of NeuN and TH in the midbrain and brainstem were gradually decreased, and the expression level of α-syn was gradually increased (P<0.05) in the exposure group with the progress of exposure time. TUNEL staining showed that the apoptosis rates of neurons in LC were gradually increased (P<0.05) in the exposure group with the progress of exposure time. Conclusion: PQ induces progressive damage in the LC area of PD-like mice, which may be caused by the abnormal accumulation of pathological α-syn in the LC area.
Animals ; Dopaminergic Neurons ; Locus Coeruleus/pathology* ; Male ; Mice ; Mice, Inbred C57BL ; Paraquat/toxicity* ; Parkinson Disease/metabolism* ; Substantia Nigra ; Tyrosine 3-Monooxygenase/metabolism*