Lack of long-term changes in circadian, locomotor, and cognitive functions in acute and chronic MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) mouse models of parkinson’s disease

Neurochemical, histological, and behavioral profiling of the acute, sub-acute, and chronic MPTP mouse model of Parkinson's disease

Parkinson's disease (PD) is a heterogeneous multi-systemic disorder unique to humans characterized by motor and non-motor symptoms. Preclinical experimental models of PD present limitations and inconsistent neurochemical, histological, and behavioral readouts. The 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of PD is the most common in vivo screening platform for novel drug therapies; nonetheless, behavioral endpoints yielded amongst laboratories are often discordant and inconclusive. In this study, we characterized neurochemically, histologically, and behaviorally three different MPTP mouse models of PD to identify translational traits reminiscent of PD symptomatology. MPTP was intraperitoneally (i.p.) administered in three different regimens: (i) acute-four injections of 20 mg/kg of MPTP every 2 h; (ii) sub-acute-one daily injection of 30 mg/kg of MPTP for 5 consecutive days; and (iii) chronic-one daily injection of 4 mg/kg of MPTP for 28 consecutive days. A series of behavioral tests were conducted to assess motor and non-motor behavioral changes including anxiety, endurance, gait, motor deficits, cognitive impairment, circadian rhythm and food consumption. Impairments in balance and gait were confirmed in the chronic and acute models, respectively, with the latter showing significant correlation with lesion size. The sub-acute model, by contrast, presented with generalized hyperactivity. Both, motor and non-motor changes were identified in the acute and sub-acute regime where habituation to a novel environment was significantly reduced. Moreover, we report increased water and food intake across all three models. Overall, the acute model displayed the most severe lesion size, while across the three models striatal dopamine content (DA) did not correlate with the behavioral performance. The present study demonstrates that detection of behavioral changes following MPTP exposure is challenging and does not correlate with the dopaminergic lesion extent.

Modeling of the Progressive Degradation of the Nigrostriatal Dopaminergic System in Mice to Study the Mechanisms of Neurodegeneration and Neuroplasticity in Parkinson's Disease

The fight against neurodegenerative diseases, including Parkinson's disease (PD), is among the global challenges of the 21st century. The low efficiency of therapy is due to the late diagnosis and treatment of PD, which take place when there is already significant degradation of the nigrostriatal dopaminergic system, a key link in the regulation of motor function. We have developed a subchronic mouse model of PD by repeatedly administering 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) at gradually increasing doses with a 24 h interval between injections, a period comparable to the time of MPTP metabolism and elimination from the body. This model reproduces the main hallmarks of PD: progressive degeneration of dopaminergic neurons; the appearance of motor disorders with a 70-80% decrease in the level of dopamine in the striatum; an increase in dopamine turnover in the striatum to compensate for dopamine deficiency. When comparing the degradation of the nigrostriatal dopaminergic system and motor disorders in mice in the acute and subchronic models of PD, it has turned out that the resistance of dopaminergic neurons to MPTP increases with its repeated administration. Our subchronic model of PD opens up broad prospects for studying the molecular mechanisms of PD pathogenesis and developing technologies for early diagnosis and preventive treatment.

Sleep and circadian rhythms in Parkinson's disease and preclinical models

The use of animals as models of human physiology is, and has been for many years, an indispensable tool for understanding the mechanisms of human disease. In Parkinson's disease, various mouse models form the cornerstone of these investigations. Early models were developed to reflect the traditional histological features and motor symptoms of Parkinson's disease. However, it is important that models accurately encompass important facets of the disease to allow for comprehensive mechanistic understanding and translational significance. Circadian rhythm and sleep issues are tightly correlated to Parkinson's disease, and often arise prior to the presentation of typical motor deficits. It is essential that models used to understand Parkinson's disease reflect these dysfunctions in circadian rhythms and sleep, both to facilitate investigations into mechanistic interplay between sleep and disease, and to assist in the development of circadian rhythm-facing therapeutic treatments. This review describes the extent to which various genetically- and neurotoxically-induced murine models of Parkinson's reflect the sleep and circadian abnormalities of Parkinson's disease observed in the clinic.

Experimental Models of Cognitive Impairment for Use in Parkinson's Disease Research: The Distance Between Reality and Ideal

Parkinson’s disease (PD) is the second most common neurodegenerative disease. Cognitive impairment is one of the key non-motor symptoms of PD, affecting both mortality and quality of life. However, there are few experimental studies on the pathology and treatments of PD with mild cognitive impairment (PD-MCI) and PD dementia (PDD) due to the lack of representative models. To identify new strategies for developing representative models, we systematically summarized previous studies on PD-MCI and PDD and compared differences between existing models and diseases. Our initial search identified 5432 articles, of which 738 were duplicates. A total of 227 articles met our inclusion criteria and were included in the analysis. Models fell into three categories based on model design: neurotoxin-induced, transgenic, and combined. Although the neurotoxin-induced experimental model was the most common type that was used during every time period, transgenic and combined experimental models have gained significant recent attention. Unfortunately, there remains a big gap between ideal and actual experimental models. While each model has its own disadvantages, there have been tremendous advances in the development of PD models of cognitive impairment, and almost every model can verify a hypothesis about PD-MCI or PDD. Finally, our proposed strategies for developing novel models are as follows: a set of plans that integrate symptoms, biochemistry, neuroimaging, and other objective indicators to judge and identify that the novel model plays a key role in new strategies for developing representative models; novel models should simulate different clinical features of PD-MCI or PDD; inducible α-Syn overexpression and SH-SY5Y-A53T cellular models are good candidate models of PD-MCI or PDD.

Microglial activation contributes to cognitive impairments in rotenone-induced mouse Parkinson's disease model

Background

Cognitive decline occurs frequently in Parkinson’s disease (PD), which greatly decreases the quality of life of patients. However, the mechanisms remain to be investigated. Neuroinflammation mediated by overactivated microglia is a common pathological feature in multiple neurological disorders, including PD. This study is designed to explore the role of microglia in cognitive deficits by using a rotenone-induced mouse PD model.

Methods

To evaluate the role of microglia in rotenone-induced cognitive deficits, PLX3397, an inhibitor of colony-stimulating factor 1 receptor, and minocycline, a widely used antibiotic, were used to deplete or inactivate microglia, respectively. Cognitive performance of mice among groups was detected by Morris water maze, objective recognition, and passive avoidance tests. Neurodegeneration, synaptic loss, α-synuclein phosphorylation, glial activation, and apoptosis were determined by immunohistochemistry and Western blot or immunofluorescence staining. The gene expression of inflammatory factors and lipid peroxidation were further explored by using RT-PCR and ELISA kits, respectively.

Results

Rotenone dose-dependently induced cognitive deficits in mice by showing decreased performance of rotenone-treated mice in the novel objective recognition, passive avoidance, and Morris water maze compared with that of vehicle controls. Rotenone-induced cognitive decline was associated with neurodegeneration, synaptic loss, and Ser129-phosphorylation of α-synuclein and microglial activation in the hippocampal and cortical regions of mice. A time course experiment revealed that rotenone-induced microglial activation preceded neurodegeneration. Interestingly, microglial depletion by PLX3397 or inactivation by minocycline significantly reduced neuronal damage and α-synuclein pathology as well as improved cognitive performance in rotenone-injected mice. Mechanistically, PLX3397 and minocycline attenuated rotenone-induced astroglial activation and production of cytotoxic factors in mice. Reduced lipid peroxidation was also observed in mice treated with combined PLX3397 or minocycline and rotenonee compared with rotenone alone group. Finally, microglial depletion or inactivation was found to mitigate rotenone-induced neuronal apoptosis.

Conclusions

Taken together, our findings suggested that microglial activation contributes to cognitive impairments in a rotenone-induced mouse PD model via neuroinflammation, oxidative stress, and apoptosis, providing novel insight into the immunopathogensis of cognitive deficits in PD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-020-02065-z.

Shared cerebral metabolic pathology in non-transgenic animal models of Alzheimer's and Parkinson's disease

Parkinson's disease (PD) and Alzheimer's disease (AD) are the most common chronic neurodegenerative disorders, characterized by motoric dysfunction or cognitive decline in the early stage, respectively, but often by both symptoms in the advanced stage. Among underlying molecular pathologies that PD and AD patients have in common, more attention is recently paid to the central metabolic dysfunction presented as insulin resistant brain state (IRBS) and altered cerebral glucose metabolism, both also explored in animal models of these diseases. This review aims to compare IRBS and alterations in cerebral glucose metabolism in representative non-transgenic animal PD and AD models. The comparison is based on the selectivity of the neurotoxins which cause experimental PD and AD, towards the cellular membrane and intracellular molecular targets as well as towards the selective neurons/non-neuronal cells, and the particular brain regions. Mitochondrial damage and co-expression of insulin receptors, glucose transporter-2 and dopamine transporter on the membrane of particular neurons as well as astrocytes seem to be the key points which are further discussed in a context of alterations in insulin signalling in the brain and its interaction with dopaminergic transmission, particularly regarding the time frame of the experimental AD/PD pathology appearance and the correlation with cognitive and motor symptoms. Such a perspective provides evidence on IRBS being a common underlying metabolic pathology and a contributor to neurodegenerative processes in representative non-transgenic animal PD and AD models, instead of being a direct cause of a particular neurodegenerative disorder.

Sleep Disorders in Rodent Models of Parkinson's Disease

Sleep disorders are frequently diagnosed in Parkinson's disease and manifested in the prodromal and advanced stages of the disease. These conditions, which in some cases affect more than 50% of Parkinson's disease (PD) patients, include hypersomnia, often manifested as excessive daytime sleepiness, insomnia, characterized by delayed initiation and fragmentation of sleep at night, and disruption of rapid eye movement (REM) sleep, resulting in loss of atonia and dream enactment. Standard dopamine replacement therapies for the treatment of motor symptoms are generally inadequate to combat sleep abnormalities, which seriously affect the quality of life of PD patients. Rodent models still represent a major tool for the study of many aspects of PD. They have been primarily designed to eliminate midbrain dopamine neurons and elicit motor impairment, which are the traditional pathological features of PD. However, rodent models are increasingly employed to investigate non-motor symptoms, which are often caused by degenerative processes affecting multiple monoaminergic and peptidergic structures. This review describes how neurotoxic and genetic manipulations of rats and mice have been utilized to reproduce some of the major sleep disturbances associated with PD and to what extent these abnormalities can be linked to nondopaminergic dysfunction, affecting for instance noradrenaline, serotonin, and orexin transmission. Strengths and limitations are discussed, as well as the consistency of results obtained so far, and the need for models that better reproduce the multisystemic neurodegenerative nature of PD, thereby allowing to replicate the complex etiology of sleep-related disorders.

Circadian Rhythm Abnormalities in Parkinson's Disease from Humans to Flies and Back

Clinical and research studies have suggested a link between Parkinson’s disease (PD) and alterations in the circadian clock. Drosophila melanogaster may represent a useful model to study the relationship between the circadian clock and PD. Apart from the conservation of many genes, cellular mechanisms, signaling pathways, and neuronal processes, Drosophila shows an organized central nervous system and well-characterized complex behavioral phenotypes. In fact, Drosophila has been successfully used in the dissection of the circadian system and as a model for neurodegenerative disorders, including PD. Here, we describe the fly circadian and dopaminergic systems and report recent studies which indicate the presence of circadian abnormalities in some fly PD genetic models. We discuss the use of Drosophila to investigate whether, in adults, the disruption of the circadian system might be causative of brain neurodegeneration. We also consider approaches using Drosophila, which might provide new information on the link between PD and the circadian clock. As a corollary, since PD develops its symptomatology over a large part of the organism’s lifespan and given the relatively short lifespan of fruit flies, we suggest that genetic models of PD could be used to perform lifelong screens for drug-modulators of general and/or circadian-related PD traits.

Trx-1 ameliorates learning and memory deficits in MPTP-induced Parkinson's disease model in mice

Parkinson's disease (PD) is characterized by a progressive loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc), characteristic motor symptoms and cognitive impairment. Thioredoxin-1 (Trx-1) is a redox protein and protects neurons from various injuries. Our previous study has shown that Trx-1 overexpression attenuates movement disorder in PD. However, whether Trx-1 ameliorates cognitive deficits in PD is still unknown. In the present study, we investigated the effects of Trx-1 on learning and memory in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD model in mice. We demonstrated that deficits in learning and memory were induced by MPTP in mice through the elevated plus-maze test. We found that the retention transfer latency time was shorten, escape latency was decreased and the number of platform crossings was increased in the Morris water maze (MWM) in Trx-1 transgenic (TG) mice when compared with wild type mice. The expressions of tyrosine hydroxylase (TH) and dopamine D1 receptor (D1R) were decreased by MPTP, which were restored in Trx-1 TG mice. The expression of N-methyl-D-aspartate receptor 2B subunit (NR2B), the levels of phosphorylation of extracellular signal-regulated kinase (ERK1/2) and cAMP-response element binding protein (CREB) in the hippocampus were decreased by MPTP, which were reversed in Trx-1 TG mice. These results suggest that Trx-1 ameliorates learning and memory deficits in MPTP-induced PD model in mice via modulating the D1R and the NMDAR-ERK1/2-CREB pathway. Trx-1 may be a therapy target for learning and memory deficits in PD.

Effects of Sub-Chronic MPTP Exposure on Behavioral and Cognitive Performance and the Microbiome of Wild-Type and mGlu8 Knockout Female and Male Mice

Motor dysfunction is a hallmark of Parkinson's disease (PD); however, non-motor symptoms such as gastrointestinal dysfunction often arise prior to motor symptoms. Alterations in the gut microbiome have been proposed as the earliest event in PD pathogenesis. PD symptoms often demonstrate sex differences. Glutamatergic neurotransmission has long been linked to PD pathology. Metabotropic glutamate receptors (mGlu), a family of G protein-coupled receptors, are divided into three groups, with group III mGlu receptors mainly localized presynaptically where they can inhibit glutamate release in the CNS as well as in the gut. Additionally, the gut microbiome can communicate with the CNS via the gut-brain axis. Here, we assessed whether deficiency of metabotropic glutamate receptor 8 (mGlu8), group III mGlu, modulates the effects of the neurotoxin, 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), on behavioral and cognitive performance in female and male mice. We studied whether these effects are associated with changes in striatal tyrosine hydroxylase (TH) levels and the gut microbiome. Two-week sub-chronic MPTP increased activity of female and male wild-type (WT) and mGlu8 knockout (KO) mice in the open field. MPTP also showed genotype- and sex-dependent effects. MPTP increased the time WT, but not KO, females and males spent exploring objects. In WT mice, MPTP improved sensorimotor function in males but impaired it in females. Further, MPTP impaired cued fear memory in WT, but not KO, male mice. MPTP reduced striatal TH levels in WT and KO mice but these effects were only pronounced in males. MPTP treatment and genotype affected the diversity of the gut microbiome. In addition, there were significant associations between microbiome α-diversity and sensorimotor performance, as well as microbiome composition and fear learning. These results indicate that specific taxa may directly affect motor and fear learning or that the same physiological effects that enhance both forms of learning also alter diversity of the gut microbiome. MPTP's effect on motor and cognitive performance may then be, at least in part, be mediated by the gut microbiome. These data also support mGlu8 as a novel therapeutic target for PD and highlight the importance of including both sexes in preclinical studies.

The effect of directed photic stimulation of the pineal on experimental Parkinson's disease

The role of the circadian system in Parkinson's disease (PD) is a topic of increasing scientific interest. This has emerged from recent studies demonstrating an altered response of PD patients to treatment in relation to the phase of the light/dark cycle and from other work defining the functional significance of melanocytes in PD: a cell type that the nigro-striatal dopamine (NSD) system and circadian system both contain. The present study was undertaken to determine the sensitivity of the pineal, as the final common pathway of the circadian system, to light delivered directly to the pineal via surgical implantation of LEDs. Direct photic stimulation of the pineal altered the course of experimental PD while anatomical controls receiving stimulation of the frontal cortex exhibited a negative impact on the course of recovery of these animals. These effects were closely linked to the phase of the light/dark cycle. The present results suggest that while pineal photoreceptors are regarded as vestigial, functional photo-reactivity of the pineal remains. It is inferred that melanocytes are the active cells responsible for the observed effect since they remain functionally intact in mammalian pineal even though pineal photoreceptors are functionally inert. Although the stimuli applied in the present study may be regarded as artificial this study demonstrates that brain parenchyma remains differentially reactive to direct light exposure and presents a novel mechanism in circadian structures that needs to be explored.

Circadian system - A novel diagnostic and therapeutic target in Parkinson's disease?

The circadian system regulates biological rhythmicity in the human body. The role of the circadian system in neurological disorders is a theme that is attracting an increasing amount of interest from the scientific community. This has arisen, in part, from emerging evidence that disorders such as Parkinson's disease (PD) are multifactorial with many features exhibiting diurnal fluctuations, thereby suggestive of circadian involvement. Although the importance of fluctuating motor and nonmotor manifestations in PD have been well acknowledged, the role of the circadian system has received little attention until recently. It is proposed that intervening with circadian function provides a novel research avenue down which new strategies for improving symptomatic treatment and slowing of the progressive degenerative process can be approached to lessen the burden of PD. In this article we review the literature describing existing circadian research in PD and its experimental models.

Executive function deficits and glutamatergic protein alterations in a progressive 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine mouse model of Parkinson's disease

Changes in executive function are at the root of most cognitive problems associated with Parkinson's disease. Because dopaminergic treatment does not necessarily alleviate deficits in executive function, it has been hypothesized that dysfunction of neurotransmitters/systems other than dopamine (DA) may be associated with this decrease in cognitive function. We have reported decreases in motor function and dopaminergic/glutamatergic biomarkers in a progressive 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) Parkinson's mouse model. Assessment of executive function and dopaminergic/glutamatergic biomarkers within the limbic circuit has not previously been explored in our model. Our results show progressive behavioral decline in a cued response task (a rodent model for frontal cortex cognitive function) with increasing weekly doses of MPTP. Although within the dorsolateral (DL) striatum mice that had been given MPTP showed a 63% and 83% loss of tyrosine hydroxylase and dopamine transporter expression, respectively, there were no changes in the nucleus accumbens or medial prefrontal cortex (mPFC). Furthermore, dopamine-1 receptor and vesicular glutamate transporter (VGLUT)-1 expression increased in the mPFC following DA loss. There were significant MPTP-induced decreases and increases in VGLUT-1 and VGLUT-2 expression, respectively, within the DL striatum. We propose that the behavioral decline following MPTP treatment may be associated with a change not only in cortical-cortical (VGLUT-1) glutamate function but also in striatal DA and glutamate (VGLUT-1/VGLUT-2) input.

α-Asarone attenuates microglia-mediated neuroinflammation by inhibiting NF kappa B activation and mitigates MPTP-induced behavioral deficits in a mouse model of Parkinson's disease

The selective loss of dopaminergic neurons in Parkinson's disease (PD) is associated with microglial activation. Therefore, the importance of early therapeutic intervention to inhibit microglial activation would be an effective strategy to alleviate the progression of PD. α-Asarone, an active compound found in Araceae and Annonaceae plant species has been used to improve various disease conditions including central nervous system disorders. In the present study the in vitro and in vivo therapeutic effects of α-asarone isolated from the rhizome of Acorus gramineus Solander was evaluated on microglia-mediated neuroinflammation and neuroprotection. Lipopolysaccharide (LPS)-stimulated BV-2 microglial cells were used to evaluate in vitro effects. 1-methyl-4 phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)-induced mouse model of PD was developed to study the neuroprotective effects of α-asarone in vivo. The results indicated that α-asarone significantly attenuated the LPS-stimulated increase in neuroinflammatory responses and suppressed pro-inflammatory cytokine production in BV-2 cells. Mechanistic study revealed that α-asarone inhibited the LPS-stimulated activation via regulation of nuclear factor kappa-B by blocking degradation of inhibitor kappa B-alpha signaling in BV-2 microglial cells. In in vivo studies, MPTP intoxication to mice resulted in brain microglial activation and significant behavioral deficits. Prophylactic treatment with α-asarone suppressed microglial activation and attenuated PD-like behavioral impairments as assessed by the Y-maze and pole tests. Taken together, these data demonstrate that α-asarone is a promising neuroprotective agent that should be further evaluated and developed for future prevention and treatment of microglia-mediated neuroinflammatory conditions including PD.

TNF-α regulates miRNA targeting mitochondrial complex-I and induces cell death in dopaminergic cells

Parkinson's disease (PD) is a complex neurological disorder of the elderly population and majorly shows the selective loss of dopaminergic (DAergic) neurons in the substantia nigra pars compacta (SNpc) region of the brain. The mechanisms leading to increased cell death of DAergic neurons are not well understood. Tumor necrosis factor-alpha (TNF-α), a pro-inflammatory cytokine is elevated in blood, CSF and striatum region of the brain in PD patients. The increased level of TNF-α and its role in pathogenesis of PD are not well understood. In the current study, we investigated the role of TNF-α in the regulation of cell death and miRNA mediated mitochondrial functions using, DAergic cell line, SH-SY5Y (model of dopaminergic neuron degeneration akin to PD). The cells treated with low dose of TNF-α for prolonged period induce cell death which was rescued in the presence of zVAD.fmk, a caspase inhibitor and N-acetyl-cysteine (NAC), an antioxidant. TNF-α alters mitochondrial complex-I activity, decreases adenosine triphosphate (ATP) levels, increases reactive oxygen species levels and mitochondrial turnover through autophagy. TNF-α differentially regulates miRNA expression involved in pathogenesis of PD. Bioinformatics analysis revealed that the putative targets of altered miRNA included both pro/anti apoptotic genes and subunits of mitochondrial complex. The cells treated with TNF-α showed decreased level of nuclear encoded transcript of mitochondrial complexes, the target of miRNA. To our knowledge, the evidences in the current study demonstrated that TNF-α is a potential regulator of miRNAs which may regulate mitochondrial functions and neuronal cell death, having important implication in pathogenesis of PD.

Loss of dopamine disrupts circadian rhythms in a mouse model of Parkinson's disease

Although a wide range of physiological functions regulated by dopamine (DA) display circadian variations, the role of DA in the generation and/or modulation of these rhythms is unknown. In Parkinson's disease (PD) patients, in addition to the classical motor symptoms, disturbances of the pattern of daily rest/wake cycles are common non-motor symptoms. We investigated daily and circadian rhythms of rest/activity behaviors in a transgenic MitoPark mouse model with selective inactivation of mitochondrial transcription factor A (Tfam) resulting in a slow and progressive degeneration of DA neurons in midbrain structures. Correlated with this, MitoPark mice show a gradual reduction in locomotor activity beginning at about 20weeks of age. In a light-dark cycle, MitoPark mice exhibit a daily pattern of rest/activity rhythms that shows an age-dependent decline in both the amplitude and the stability of the rhythm, coupled with an increased fragmentation of day/night activities. When the circadian system is challenged by exposure to constant darkness or constant light conditions, control littermates retain a robust free-running circadian locomotor rhythm, whereas in MitoPark mice, locomotor rhythms are severely disturbed or completely abolished. Re-exposure to a light/dark cycle completely restores daily locomotor rhythms. MitoPark mice and control littermates express similar masking behaviors under a 1h light/1h dark regime, suggesting that the maintenance of a daily pattern of rest/activity in arrhythmic MitoPark mice can be attributed to the acute inhibitory and stimulatory effects of light and darkness. These results imply that, in addition to the classical motor abnormalities observed in PD, the loss of the midbrain DA neurons leads to impairments of the circadian control of rest/activity rhythms.

Isolation of the sapogenin from defatted seeds of Camellia oleifera and its neuroprotective effects on dopaminergic neurons

Sasanqua saponin is a major active compound in the defatted seeds of Camellia oleifera but is always discarded without effective utilization. The sapogenin from hydrolysis of sasanqua saponin was purified, and its amination derivative was investigated on its neuroprotective effects, which were evaluated by animal models of Parkinson disease in mice induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). The results showed that the sapogenin and its derivative increased dopamine content in striatum and tyrosine hydroxylase (TH) positive cells in substantia nigra and relieved inflammation and behavioral disorder, but the effect on movement was reversed by dopamine receptor antagonist haloperidol and was not intervened by adenosine receptor antagonist CGS 15943. Molecular simulation showed the interaction between dopamine receptor and the sapogenin or its derivative. It is proven that the sapogenin can protect dopamine neurons through antineuroinflammation and activation of dopamine receptor rather than adenosine receptor, and its amination improves the effects. This research provides the prospective prodrugs for Parkinson disease and a new medicinal application of sasanqua saponin.

Alteration of daily and circadian rhythms following dopamine depletion in MPTP treated non-human primates

Disturbances of the daily sleep/wake cycle are common non-motor symptoms of Parkinson's disease (PD). However, the impact of dopamine (DA) depletion on circadian rhythms in PD patients or non-human primate (NHP) models of the disorder have not been investigated. We evaluated alterations of circadian rhythms in NHP following MPTP lesion of the dopaminergic nigro-striatal system. DA degeneration was assessed by in vivo PET ([(11)C]-PE2I) and post-mortem TH and DAT quantification. In a light∶dark cycle, control and MPTP-treated NHP both exhibit rest-wake locomotor rhythms, although DA-depleted NHP show reduced amplitude, decreased stability and increased fragmentation. In all animals, 6-sulphatoxymelatonin peaks at night and cortisol in early morning. When the circadian system is challenged by exposure to constant light, controls retain locomotor rest-wake and hormonal rhythms that free-run with stable phase relationships whereas in the DA-depleted NHP, locomotor rhythms are severely disturbed or completely abolished. The amplitude and phase relations of hormonal rhythms nevertheless remain unaltered. Use of a light-dark masking paradigm shows that expression of daily rest-wake activity in MPTP monkeys requires the stimulatory and inhibitory effects of light and darkness. These results suggest that following DA lesion, the central clock in the SCN remains intact but, in the absence of environmental timing cues, is unable to drive downstream rhythmic processes of striatal clock gene and dopaminergic functions that control locomotor output. These findings suggest that the circadian component of the sleep-wake disturbances in PD is more profoundly affected than previously assumed.