Parkinson's disease (PD) is the second most prevalent age-related neurodegenerative disease and currently affects over 8 million people worldwide. The primary features of PD include cognitive, behavioral, and motor function deficits induced primarily by the progressive loss of dopaminergic neurons within the substantia nigra of the basal ganglia (BG). Motor coordination becomes severely affected over the course of the disease, causing patients to experience tremors at rest, bradykinesia, and body rigidity. The availability of treatment options has increased the quality of life for patients experiencing the early stages of PD; however, there exists no cure and treatment options are limited for those experiencing severe, advanced disease symptoms. Genetic studies in PD patients have led to the identification of causative genes, but revealed that less than 20% of cases can be attributed to monogenic variations. Evidence strongly indicates that the majority of PD cases are idiopathic and likely driven due to gene by environmental interactions. Reflective of this idea, recent research efforts have turned to genome-wide association studies (GWAS) to provide indications of gene variations, that while not causative of PD, incur increased risk within patient populations. GWAS findings play a particularly crucial role in neurodegenerative interventions, as early identification of patient risk may allow for preventative therapeutics to delay disease onset or reduce symptom severity. Amongst the many gene variants identified as incurring increased PD risk, single-nucleotide polymorphisms (SNPs) in the loci for CD38 that cause reduced gene expression are consistently identified as increasing risk. The cluster of differentiation 38 (CD38) protein serves two major roles: one as a receptor for immunological response and a second as an ectoenzyme that modulates bioenergetic functions. The particular functions of CD38 are highly relevant to neurodegenerative contexts, as changes in central nervous system (CNS) inflammatory status and means of cellular energy production typically precede pathological indications. In the brain, CD38 expression is most enriched in astrocytes in BG regions, including substantia nigra, midbrain, and striatum. However, it is not known how CD38 deficiency may contribute to astrocytic dysfunction and neuropathological features of PD. This dissertation describes how CD38 influences astrocytic gene expression and cellular bioenergetics. Astrocyte RNA was sequenced from the BG of one-year old male Cd38+/+, Cd38+/-, and Cd38-/- mice by magnetic-activated cell sorting (MACS) to acquire astrocyte isolates. Numerous differentially expressed genes (DEGs) were identified in Cd38 Cd38+/- and Cd38-/- astrocytes that relate to regulation of cellular health, responses to stress, and bioenergetic functions. GO analysis further suggested mitochondrial dysfunction in both Cd38+/- and Cd38-/- astrocytes. In a subsequent set of experiments evaluating mitochondrial function by Seahorse XF96 platform, Cd38+/- and Cd38-/- astrocytes displayed altered bioenergetic function. The results herein demonstrate that astrocytic Cd38 expression regulates cellular function and implicates transcriptional changes associated with the hallmarks of neurodegeneration. These findings serve to provide future direction for studies evaluating the relationship between CD38 function and astrocytes as it relates to neurodegenerative PD risk. / Doctor of Philosophy / Parkinson's disease (PD) is the second most common age-related neurodegenerative disease and currently affects over 8 million people worldwide. The primary features of PD include cognitive, behavioral, and motor function deficits induced primarily by the progressive loss of specialized neurons within the substantia nigra of the basal ganglia (BG) brain region. Motor coordination becomes severely affected over the course of the disease, causing patients to experience body tremors, slowness, and rigidity. The availability of treatment options has increased the quality of life for patients experiencing the early stages of PD; however, there exists no cure and little treatment options for those experiencing severe, advanced disease symptoms. Genetic studies in PD patients have led to the identification of causative genes, but revealed that less than 20% of cases can be attributed to specific, individual variations. Evidence strongly indicates that the majority of PD cases are likely caused by small gene changes that interact with environmental factors. Recent research efforts have turned to genome-wide association studies (GWAS) to identify these small changes, that while not causative of PD, may increase risk within patient populations. GWAS findings play a particularly crucial role in treating neurodegenerative diseases, as early identification of patient risk may allow for preventative therapeutics to slow disease onset or reduce symptom severity. Amongst the many small gene changes identified as increasing PD risk, changes in the gene CD38 that cause reduced gene expression are consistently identified as increasing risk. The cluster of differentiation 38 (CD38) protein serves two major roles: one as a receptor for immune responses and a second as an enzyme that impacts how cells produce energy. The functions of CD38 are highly relevant to neurodegenerative contexts, as changes in central nervous system (CNS) inflammatory status and means of cellular energy production typically precede disease pathology. In the brain, CD38 expression is most enriched in astrocytes, specialized brain cells that supports neurons, in regions affected by PD. However, it is not known how CD38 deficiency may contribute to astrocytic dysfunction and neuropathological features of PD. This dissertation describes how CD38 influences astrocytic gene expression and cellular bioenergetics. Astrocyte RNA was sequenced from the BG of one-year old male Cd38+/+, Cd38+/- (50% CD38 loss), and Cd38-/- (100% CD38 loss) mice by magnetic-activated cell sorting (MACS) to acquire astrocytes. Numerous changes in gene expression were identified in Cd38 Cd38+/- and Cd38-/- astrocytes that relate to regulation of cellular health, responses to stress, and energy functions. Further analysis looking at functions, suggested mitochondrial abnormalities in both Cd38+/- and Cd38-/- astrocytes. In a subsequent set of experiments evaluating mitochondrial function by Seahorse XF96 platform, Cd38+/- and Cd38-/- astrocytes displayed altered energetic function. The results herein demonstrate that astrocytic Cd38 expression regulates cellular function and implicates transcriptional changes associated with the hallmarks of neurodegeneration. These findings serve to provide future direction for studies evaluating the relationship between CD38 function and astrocytes as it relates to neurodegenerative PD risk.

Self-administration of 1-methyl-4-pheny]-1,2,3,6-tetrahydropyridine (MPTP) has resulted in irreversible symptoms of Parkinson's disease in several young drug abusers. It was found that this neurotoxicant selectively destroys neuronal cells in the substantia nigra of humans and other primates. Although the mechanism of action of MPTP is not fully understood, it is now generally believed that the crucial species for MPTP neurotoxicity is not MPTP itself, but rather some of its metabolites. MPDP⁺, an intermediate in the metabolism of the neurotoxin MPTP, was found to generate superoxide radical (⋅O₂⁻) during its autoxidation process. The generation of ⋅O₂⁻ was detected by their ability to reduce ferricytochrome c. Superoxide dismutase (SOD) inhibited this reduction in a dosedependent manner. The rate of reduction of ferricytochrome c was dependent not only on the concentration of MPDP⁺, but also on the pH of the system. Thus, the rate of autoxidation of MPDP⁺ and the sensitivity of this autoxidation to superoxide dismutase inhibitable ferricytochrome c reduction were both augmented as the pH was raised from 7.0 to 10.5. The rate constant (k_c) for the reaction of superoxide radical with ferricytochrome c to form ferrocytochrome c was found to be 3.48 x 10⁵ M⁻¹S⁻¹. The rate constant (k_MPDP⁺) for the reaction of MPDP⁺ with ferricytochrome c was found to be 4.86 M⁻¹S⁻¹. The generation of ⋅O₂⁻ was further confirmed by spin-trapping in combination with EPR techniques using 5, 5-dimethyl-1-pyrrolonine-N-oxide (DMPO) as the spin trapping agent. The rate of formation of spin adduct (DMPO-O₂⁻) was dependent not only on the concentrations of MPDP⁺ and oxygen but also on the pH of the system. Superoxide dismutase inhibited the spin adduct formation in a dose-dependent manner. The ability of DMPO to trap superoxide radicals, generated during the autoxidation of MPDP⁺, and of SOD to effectively compete with this reaction for the available ⋅O₂⁻, was used as a convenient competition reaction to quantitatively determine various kinetic parameters. Using this technique, the rate constant for scavenging of superoxide radicals by superoxide dismutase was found to be 7.56 x 10⁹ M⁻¹S⁻¹. The maximum rate of superoxide generation at a fixed spin trap concentration using different amounts of MPDP⁺ was found to be 4.48 x 10⁻¹⁰ M⋅S⁻¹. The rate constant (k₁) for MPDP⁺ making superoxide radical was found to be 3.97 x 10⁻⁶ Sec⁻¹. The second order rate constant (k_DMPO) for DMPO trapping superoxide radicals was found to be 10.2 M⁻¹S⁻¹. The life time of superoxide radical at pH 10.0 was calculated to be 1.25 seconds. These data indicate that superoxide radicals are produced during spontaneous oxidation of MPDP⁺ and that EPR spin trapping techniques can be used to determine the rate constants and life time of free radicals generated in aqueous solution. Monoamine oxidase type B (MAO-B), an enzyme present in mitochondrial membranes, is known to metabolize MPTP to MPDP⁺, which then spontaneously oxidizes to MPP⁺. In the studies of MAO-B catalyzed oxidation of MPTP, the neurotoxicant was found to generate reactive oxygen species during its interaction with the enzyme. The kinetic parameters, K_m and V_max, for MAO-B catalyzed oxidation of MPTP to the corresponding species MPDP⁺ were found to be 0.194 mM and 0.335 µM/min, respectively. The generation of ⋅O₂⁻ and hydroxyl (⋅OH) radicals was detected as the DMPO spin adduct by spin trapping in combination with EPR techniques. Addition of Fe²⁺ (10 µM) to this system caused a 5-fold enhancement in EPR signal intensity of the DMPO-OH adduct. Catalase, a scavenger of hydrogen peroxide (H₂O₂), inhibited the DMPO-OH spin adduct formation in a dose-dependent manner, indicating that H₂O₂ is produced in the MAO-B catalyzed oxidation of MPTP. Ethanol, a well known scavenger of hydroxy] radical, rapidly produced an alpha-hydroxyethyl radical signal. SOD inhibited the formation of DMPO-O₂⁻ and DMPO-OH spin adducts in a dose-dependent fashion. These data suggest that ⋅O₂⁻ are produced during the oxidation of MPTP by MAO-B and that the generation of H₂O₂ and ⋅OH was secondary to the production of ⋅O₂⁻. MPTP and its metabolites, MPDP⁺ and MPP⁺, were found to inhibit the activity of acetylcholinesterase (AChE). The kinetic parameter, K_m for the substrate (acetylthiocholine), was found to be 0.216 mM and K_i values for MPTP, MPDP⁺ and MPP⁺ to inactivate AChE were found to be 2.14, 0.265 and 0.197 mM, respectively. The inactivation of AChE by these neurotoxicants was found to be dose-dependent. It was found that MPTP, MPDP⁺ and MPP⁺ are neither substrates of AChE nor the time-dependent inactivators. The studies of reaction kinetics indicate that the inactivation of ACHE by these inactivators is via a mixed-type inhibition. The dilution of the enzyme-inhibitor complex completely reversed the MPTP inhibition but only partially reversed the MPDP+ and MPP+ inhibition. These data indicate that MPTP and its metabolites can inactivate AChE and thereby increase ACh level in the basal ganglia of the brain, leading to potential cell dysfunction. These results suggest that once MPTP enters the basal ganglia of the brain, it can be catalyzed by MAO-B to generate a series of reactive species, including ⋅O₂⁻, H₂O₂ and ⋅OH, which are known to destroy cell membranes, enzymes and other important biological molecules. The nigrostriatal toxicity by MPTP leading to Parkinson's disease-like syndrome may largely be due to the reactivity of these reactive oxygen species in combination with the inactivation of the AChE enzyme in the brain, leading to potential cell dysfunction. / Ph. D.

Studies into the quantitative structure act! Vlty relationships of rate s of I-methyl-4-phenyl-l,2,3,6-tetrahydropyridine oxidation catalyzed by monoamine oxidases A and B were performed to elucidate active site substrate conformation and oxidation mechanisms. Plotting experimental kinetic activity against molecular properties obtained by experiment and by computational chemistry methods demonstrated correlations with lipophilic, steric, and electronic factors. Compounds studied were 4-aryloxy analogs, 4- aromatic heterocycle analogs, and 4-phenyl analogs. The conformer with phenyl ring to tetrahydropyridine dihedral angles similar to a low energy conformer of I-methyl-4-(2'-methyl-phenyl)-1,2,3,6- tetrahydropyridine is the most active conformer. Results indicate that rate limiting single electron transfer mechanisms are more viable than hydrogen atom abstraction mechanisms. Results indicate that binding or dissociation is the rate limiting step for aryloxy-analog oxidation catalyzed by monoamine oxidase B whereas the catalytic event itself is the rate limiting step for the other analogs. Several equations were developed to describe quantitative structure activity relationships of oxidation rates. / Master of Science

No description available.

Yes / This study examined the effects of providing cues to facilitate autobiographical memory retrieval in Parkinson's disease. Previous findings have shown that individuals with Parkinson's disease retrieve fewer specific autobiographical memories than older adult controls. These findings are clinically significant since the quality of autobiographical memory is linked to identity and sense of self. In the current study, 16 older adults with Parkinson's disease without dementia and 16 matched older adult controls were given 3 min in which to recall autobiographical memories associated with five different time periods and to give each memory a short title. Participants were later asked to retrieve the memories in three phases: firstly in a free recall phase; secondly in response to general cues (time periods) and finally in response to specific cues (the short titles previously given). The number of memories and the quality of the memory (general or specific) was recorded in each condition. Compared with matched older adult controls, the Parkinson's disease group was impaired in retrieving the memories that they had previously given in the free recall phase and in response to general cues. The performance of the group with Parkinson's disease was only equivalent to the older adults when they retrieved memories in response to self-generated cues. The findings are discussed in relation to theories of autobiographical memory and the neuropsychology of Parkinson's disease.

No / Instances in which we cannot retrieve information immediately but know that the information might be retrieved later are subjective states that accompany retrieval failure. These are expressed in feeling-of-knowing (FOK) and Tip-of-the-tongue (TOT) experiences. In Experiment 1, participants with Parkinson's disease (PD) and older adult controls were given general questions and asked to report when they experienced a TOT state and to give related information about the missing word. The PD group experienced similar levels of TOTs but provided less correct peripheral information related to the target when in a TOT state. In Experiment 2, participants were given a Semantic (general knowledge questions) and an Episodic (word pairs) FOK task. PD patients failed to accurately predict their future memory performance (FOK) in response to both episodic and semantic cues. Results are interpreted in the context of recent frameworks of memory and metacognition.

Thesis (PhD (Biomedical Sciences. Medical Physiology))--Stellenbosch University, 2008. / The overall objective of this thesis is to provide additional data to assist clinicians and experimental neurologists alike in the quest for better understanding, more accurately diagnosing and more successfully treating patients suffering from Parkinson’s disease (PD). The general theme of the thesis is the interaction between certain environmental stimuli, including the exposure to adverse events during early central nervous system (CNS) development and the manifestation of elements of neurodegeneration, whether by means of neurochemical changes or expressed as a dysfunctional voluntary motor system. The first chapter provides a general introduction to the research theme of the thesis. This includes, in particular, a discussion on current understanding concerning the etiology and clinical profile of PD, the relative contribution made by genetic factors compared to environmental ones, and current treatment strategies for treating the disease. Mention is also made of the failure of these therapeutic applications for reversing or protecting against the disease, due to the side-effects associated with them. The material covered in chapter 1 provides the basis for the more complete discussion concerning these various aspects, contained in the chapters to follow. The overall aim was also to characterise the effects of commonly used toxin-induced animal models of PD, and the extent of vulnerability that the CNS displays towards them. The destruction of dopaminergic neurons following the administration of 6-OHDA at targeted points along the nigrostriatal tract is used extensively to model PD pathology in rats and is an established animal model of the disease. However, mature or even aged animals are mainly used in these studies, while the effects that the toxin might have on the developing CNS remain unclear. The study reported in chapter 4 aimed to elucidate some of 6-OHDA’s actions on the young adolescent (35 days-old) CNS by comparing the motor and biochemical effects of a unilateral infusion of the toxin into two anatomically distinct basal ganglia loci: The medial forebrain bundle (MFB) and the striatum. Animals were randomly assigned to receive either a direct delivery of 6-OHDA (12μg/4μl) into the MFB or an indirect injection, into the striatum. Although both lesion types were used, the MFB model is considered a more accurate portrayal of end-stage PD, while the striatum-model better reflects the long-term progressive pathology of the disease. The different lesions’ effects on motor function were determined by observing animal’s asymmetrical forelimb use to correct for weigh shifting during the vertical exploration of a cylindrical enclosure. Following the final behavioral assessment, the concentration of dopamine (DA) and DA metabolites remaining in the post-mortem brains were determined using 4 HPLC electrochemistry (HPLC-EC) and the levels compared between the two groups. The HPLC-EC results revealed a compensatory effect for DA production and DA turnover on the lesioned hemisphere side of the toxin-infused animal group. Thus, following 6-OHDA treatment, there appears to be extensive adaptive mechanisms in place within the remaining dopaminergic terminals that may be sufficient for maintaining relatively high extracellular and synaptic concentrations of DA. However, since substantial changes in motor-function were observed, it is suggested that the capacity of the remaining dopaminergic neurons to respond to increased functional demands may be limited. In addition, the behavioral results indicate that the distinct indices relating to different functional deficits depend on the lesioning of anatomically distinct structures along the nigrostrial tract. It has long been known that far fewer women are diagnosed with PD than men are. This seeming protection offered to females against degenerative disease of the CNS may relate to estrogen, although the hormone’s mechanism of action on the dopaminergic system is poorly defined. With an estimated 10-15 million women using oral contraceptives (OCs) in the United States alone, the aim of chapter 2 was to examine the evidence for a possible relationship between PD and the female reproductive hormone estrogen. A review of the current literature available on the topic was performed by consulting Medline, and by performing a search of the case-reports contained within the World Health Organization’s (WHO) International Drug Monitoring database, for possible PD-related symptoms that may arise from estrogen replacement therapy (ERT). The results, whilst conflicting, seem to suggest that estrogen protects women from obtaining the disease, or at least some features of it. Intensive research efforts are called for, with sufficient power to establish the relationship between ERT and the onset and development of parkinsonism. Chapter 3 reports on the results obtained from an experiment that subjected young Sprague-Dawley rats, 35 days of age, to a lower and a higher dose of 6-OHDA delivered to the MFB. Control rats received equivalent saline infusions. At 14 days post-surgery, the rats were evaluated for forelimb akinesia. For the higher dose of 6- OHDA the female rats were less impaired than males in making adjustment steps in response to a weight shift and in the vibrissae-evoked forelimb placing test. In addition, Tyrosine hydroxylase (TH) immunoreactivity was significantly higher for the female rats. Early gender differences in cell survival factors and/or other promoters of neuroplasticity may have contributed to the beneficial outcome seen in the females. For example, nerve growth factor (NGF) was found to be higher in the female rats following administration of the DA neurotoxin. It is unclear whether gonadal steroids are involved, and, if so, whether female hormones are protective or whether male hormones are prodegenerative. Determining the mechanisms for the improved outcome seen in the young female rats may lead to potential treatment strategies against PD. 5 Many studies have shown that early life stress may lead to impaired brain development, and may be a risk factor for developing psychiatric diseases, including clinical depression. However, few studies have investigated the impact that early stress may have on the onset and development of neurodegenerative disorders such as PD. The study reported on in chapter 5 conjointly subjected rat pups to a maternal separation (MS) paradigm that is a well characterised model of adverse early life events, and a unilateral, intrastriatal injection of 6- OHDA. The combined effects of these models on motor deficits and brain protein levels were investigated. Specifically, the animals were assessed for behavioral changes at 28 days postlesion with a battery of tests that are sensitive to the degree of DA loss sustained. The results show that animals that had been subjected to MS display poorer performance in the vibrissae and single-limb akinesia test compared to non-MS control animals (that had also been subjected to the toxin exposure). In addition, there was a significant increase in the loss of TH staining in MS rats compared to non-MS ones. The results from this study therefore suggest that exposure to adverse experiences during the early stages of life may contribute towards making dopaminergic neurons more susceptible to subsequent insults to the CNS occurring during mature stages of life. Therefore, taken together, early exposure to stress may predispose an individual towards the onset and development of neurodegenerative disease, which especially becomes a threat during the later stages of adult life. Moreover, within the framework of these characteristics, the capacity of a widely-used pharmacological agent (statins) was tested for possible future therapeutic application in PD (chapter 7). Although the precise cause of sporadic PD remains an enigma, evidence suggests that it may associate with defective activity of complex I of the mitochondrial electron transport chain. Mitochondrial DNA transmit and express this defect in host cells, resulting in increased oxygen free radical production, depressed antioxidant enzyme activities, and greater susceptibility to apoptotic cell death. Simvastatin is a member of the 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) group of drugs that are widely used for lowering cholesterol levels in patients who display elevated concentrations of low-density lipoprotein cholesterol. The study aimed to investigate the effects that statin-treatment have on motor-function and at the mitochondrial-protein level, using rotenone, a mitochondrial complex I inhibitor, as a rat-model of PD. Adult male Sprague-Dawley rats were treated either with simvastatin (6mg/day for 14 days) or with a placebo. Two different tests to assess motor function were used: The apomorphine-rotation test, and the vibrissae-elicited forelimb placement test. Following the drug administration protocol, the nigrostriatal tract was unilaterally lesioned with either rotenone (3 μg/4 μl) or, for the controls, were sham-operated by infusing the vehicle (DMSO:PEG) only. Five days later the rats were killed and a highly purified concentration of isolated mitochondria was prepared from the substantia nigra (SN) sections. 2- 6 Dimensional electrophoresis (2-DE) with subsequent identification of the spots using electronspray ionization quadruple time-of-flight mass spectrometrical (ESI-Q-TOF MS) was performed and the results BLAST-searched using bio-informatics tools for naming the identified peptides. The motor test results indicate that while unilateral rotenone causes behavioral asymmetries, treatment with simvastatin improved motor function relative to the rotenoneinduced ones. Mass Spectroscopy identified 23 mitochondrial proteins that differ significantly in protein expression (p < 0.05) following simvastatin treatment. The altered proteins were broadly classified according to their cellular function into 6 categories, with the majority involved in energy metabolism. This study effectively illustrated how neuroproteomics, with its sophisticated techniques and non-biased ability to quantify proteins, provides a methodology with which to study the changes in neurons associated with neurodegeneration. As an emerging tool for establishing disease-associated protein profiles, it also generates a greater understanding as to how these proteins interact and undergo post-translational modifications. Furthermore, due to the advances made in bioInformatics, insight is created concerning their functional characteristics. Chapter 4 summarises the most prominent proteomics techniques and discuss major advances made in the fast-growing field of neuroproteomics in PD. Ultimately, it is hoped that the application of this technology will lead towards a presymptomatic diagnosis of PD, and the identification of risk factors and new therapeutic targets at which pharmacological intervention can be aimed. The final chapter (chapter 8) provides a retrospective look at the academic work that had been performed for the purpose of this thesis, recaps on the main findings, and also highlights certain aspects of the project and provides relevant suggestions for future research. Lastly, the appendix provides a detailed overview of the methods followed for the experiments described in this thesis. It provides not only a comprehensive description of the techniques that had been followed, but provides information concerning the care taken with the animals (i.e. post-surgery) in order to control for the potential influence of experimental variables on the results.

Adult neurogenesis is affected in neurodegenerative diseases and also represents an important therapeutic target. The goal of this dissertation research was to test the hypothesis that regeneration of neurons and glia in the adult brain can be manipulated by neurotrophic drugs in the context of two mouse models of neurodegenerative disease : Parkinson's disease and Huntington's disease.... These findings have implications for the pathophysiology of Huntington's disease and neurodegeneration in general. Specific alterations to the SVZ neurogenic niche parallel some of the pre-motor symptoms of Parkinson's disease and Huntington's disease. This dissertation research contributes to the growing body of literature concerning the pharmacological modulation of SVZ-derived neurogenesis designed to attenuate the progressive loss of neurons in neurodegenerative diseases and perhaps delay the onset of symptoms. / by Mark Harvey McCollum. / Vita. / Thesis (Ph.D.)--Florida Atlantic University, 2012. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

初級運動皮質直接負責運動控制。大量關於帕金森式癥(PD)的有效治療手段的研究已經證明，初級運動皮質在病理情況下的功能改變，直接與患者運動障礙相關。本論文的研究重點在於探索初級運動皮質在深部腦刺激治療帕金森氏症的運動障礙的過程中發揮的作用及其與運動學習功能障礙的聯繫。 / 丘腦底核深部腦刺激(STN-DBS) 已被廣泛應用於治療帕金森式症。雖然該項治療手段能顯著地改善患者的運動功能障礙，但其確切的治療機制仍未明確。理論上來說，丘腦底核深部腦刺激能夠直接啟動丘腦底核內部和其周圍很大範圍的神經組織，包括丘腦底核內部本身的神經元胞體，以及與其相連接的輸入輸出核團的神經元軸突。在丘腦底核眾多輸入核團之中，一個重要的神經輸入來自於初級運動皮質(MI)第五層的離皮質神經元(CxFn)，電刺激引起的逆行皮質啟動作用被提出，用於解釋丘腦底核深部腦刺激的治療機制。 / 為了研究逆行皮質啟動效應究竟如何在丘腦底核深部腦刺激的過程之中帶來治療效果，我們採用多通道神經電生理信號記錄系統在自由活動的單側帕金森大鼠的初級運動皮質進行鋒電位元和局部場電位元信號的記錄。實驗結果證明，當對丘腦底核進行高頻電刺激，在運動皮質第五層的離皮質神經元能成功記錄到保持固定延時的逆行鋒電位。由於增加刺激頻率會引起逆行鋒電位被成功記錄到的百分比下降，因此當深部腦刺激的頻率選擇在125Hz時，逆行鋒電位的放電頻率達到最高，而此刺激頻率正好與行為學實驗中帶來最佳治療效果的刺激頻率一致。於此同時，逆行皮質啟動作用還伴隨著初級運動皮質離皮質神經元的自發放電頻率增加、同步性爆發式放電減少等電生理信號特點。場電位分析的結果進一步表明，丘腦底核深部腦刺激減弱了病理情況下出現的beta波頻譜能量增高以及鋒電位-場電位相干性增強。更重要的是，我們發現只有逆行鋒電位被成功誘發，離皮質神經元的發放電機率才能被調節。這點有力地表明由電刺激隨機誘發的逆行鋒電位傳導至初級運動皮質，直接幹預並抑制了離皮質神經元在病理情況下的同步性爆發式放電活動，從而緩解了帕金森氏症的運動障礙。 / 另外，初級運動皮質並不僅僅是一個靜態的運動控制中樞，更為重要的功能在於它參與著與運動學習和運動記憶相關的動態資訊編碼。帕金森氏症患者普遍存在皮質可塑性減弱以及運動技能學習障礙。由於初級運動皮質分層結構的存在，層內神經元之間的突觸連接為神經可塑性提供了很好的結構基礎。因此，我們在初級運動皮質誘發在體長時程增強(LTP)，旨在研究與運動技能學習相關的皮質神經可塑性的動態變化過程，以及探索中腦多巴胺能投射系統對皮質神經可塑性的影響。 / 一方面，我們採用間斷性高頻刺激誘發在體長時程增強，證實六羥多巴損毀後皮質的長時程增強水準顯著下降。另一方面，我們設計前肢抓食的行為學範式用來評價動物在運動技能學習的不同階段皮質可塑性發生的動態變化。實驗結果表明，直接損毀皮質的多巴胺能輸入，模型組大鼠與假實驗組大鼠的行為表現在初期的技能獲取階段並無明顯差異，而只在後期的技能鞏固階段模型組大鼠表現出技能鞏固障礙。更為有趣的是，兩組行為學變化趨勢與各自的在體長時程增強的變化趨勢有很高的一致性。本研究表明多巴胺對初級運動皮質的支配在運動記憶的鞏固過程中起著關鍵作用。在帕金森氏症的病理情況下，多巴胺耗竭將影響皮質的突觸可塑性，從而造成帕金森患者在運動技能的鞏固階段表現出障礙。 / The primary motor cortex (MI) controls movement directly, but is an under-investigated brain region in the pathogenesis and treatment of Parkinsonian motor disability, when compared with the basal ganglia circuitry. In this study, the roles of MI in underlying the therapeutic action of surgical deep brain stimulation and motor learning impairment were investigated. / Deep brain stimulation of the subthalamic nucleus (STN-DBS) is now a recognized therapeutic option for Parkinson’s disease (PD). Although this surgical strategy provides behavioral benefits remarkably, its exact mechanism is still a matter of controversy. In principle, STN-DBS can directly activate a wide range of neuronal elements within the STN and surrounding areas. As the corticofugal neurons (CxFn) in the layer V motor cortex provide a major input to the STN, we hypothesized that the stimulation evoked antidromic cortical activation is involved in the therapeutic mechanism of STN-DBS. In the first series of experiments, we performed simultaneous recordings of multi-unit neuronal activities and local field potentials (LFPs) in MI in freely moving hemi-parkinsonian rats. By identifying stimulation evoked antidromic spike, which occurred at a fixed, short latency, CxFn located in the layer V MI were identified. Increasing stimulation frequency also increased failure rate of activation, resulting in a peak frequency of stochastic antidromic spikes at 125Hz STN-DBS, which was correlated with the optimal therapeutic efficacy observed in behavioral tests. Meanwhile, this antidromic effect was accompanied by the rectification of pathological neuronal activities including increased spontaneous firing rate, reduced burst discharge and synchrony among the CxFn. Field potential analysis revealed that STN-DBS alleviated the dominance of pathological beta band oscillation and spike-field coherence in the MI. More importantly, it was found that the firing probability of CxFn could only be modified following the occurrence of antidromic spikes, suggesting that direct interference of stochastic antidromic spikes with pathological neuronal activities underlies the beneficial effect of STN-DBS. / The MI is not simply a static motor control structure. It also contains a dynamic substrate that participates in motor learning or stores motor memory. In PD patients, loss of cortical plasticity and impaired motor learning is a common feature. As the intrinsic horizontal neuronal connections in MI are a strong candidate of cellular correlate for activity-dependent plasticity, in the second series of experiments, we developed in vivo long-term potentiation (LTP) technique in the MI to investigate the dynamics of cortical plasticity during motor skill learning and the role of the innervation by mesocortical dopamine input. Local depletion of dopamine in the primary motor cortex resulted in reduced performance in the forelimb reaching for food learning task. Although the performance of the PD rats in the initial learning phase was comparable to that of the sham-operated group, as training continued, these animals exhibited deficit in consolidating the motor skill. These deficits closely paralleled the impairment in training-enhanced synaptic connections in layer V neurons, and the in vivo LTP of evoked field excitatory postsynaptic potentials induced by intermittent high frequency stimulation. In addition, progressive recruitment of task-specific neurons was suppressed. Our study therefore revealed that dopamine depletion confined to the MI could lead to impairment in cortical synaptic plasticity which may preferentially affect the consolidation, but not the acquisition, of motor skills. These findings shed light on the cellular mechanisms of motor skill learning and could explain the decreased ability of PD patients in learning new motor skills. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Li, Qian. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references (leaves 168-190). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts also in Chinese. / CHAPTER 1 --- p.1 / General Introduction --- p.1 / Chapter 1.1 --- Anatomical organization of the basal ganglia --- p.1 / Chapter 1.1.1 --- Overview of the basal ganglia circuit --- p.1 / Chapter 1.1.2 --- Cortico-basal ganglia-cortical circuit --- p.1 / Chapter 1.1.2.1 --- Direct and indirect pathway --- p.2 / Chapter 1.1.2.2 --- Hyperdirect pathway --- p.2 / Chapter 1.1.2.3 --- The midbrain dopamine system --- p.2 / Chapter 1.2 --- Striatum --- p.3 / Chapter 1.2.1 --- Cell types in the striatum. --- p.3 / Chapter 1.2.2 --- The Cortico-striatal system --- p.4 / Chapter 1.3 --- Subthalamic Nucleus --- p.5 / Chapter 1.3.1 --- Neuronal property of the STN. --- p.5 / Chapter 1.3.2 --- Electrophysiological property of the STN --- p.6 / Chapter 1.3.3 --- Cortico-subthalamic system --- p.7 / Chapter 1.3.4 --- Functional significance of the cortico-subthalamic and corticostriatal system. --- p.8 / Chapter 1.4 --- Parkinson’s disease --- p.9 / Chapter 1.4.1 --- Pathogenesis of PD --- p.9 / Chapter 1.4.2 --- Genetic risk factors of PD --- p.10 / Chapter 1.4.3 --- Progressive motor symptoms of PD --- p.11 / Chapter 1.4.4 --- Non-motor symptoms of PD --- p.13 / Chapter 1.4.5 --- Pathological neuronal rhythms in the basal ganglia of PD. --- p.16 / Chapter 1.5 --- Experimental studies of PD. --- p.18 / Chapter 1.5.1 --- Animal modeling of PD. --- p.18 / Chapter 1.5.2 --- Motor deficits evaluation in rodent models of PD --- p.21 / Chapter 1.5.3 --- Non-motor symptoms evaluation in experimental models of PD --- p.24 / Chapter 1.6 --- Deep Brain Stimulation --- p.27 / Chapter 1.6.1 --- DBS in alleviating Parkinsonian motor symptoms --- p.28 / Chapter 1.6.2 --- DBS in alleviating Parkinsonian non-motor symptoms --- p.29 / Chapter 1.6.3 --- Investigation of the STN-DBS mechanism. --- p.31 / Chapter 1.6.3.1 --- Local inhibitory effect within the STN --- p.32 / Chapter 1.6.3.2 --- Excitatory effect at output nuclei --- p.33 / Chapter 1.6.3.3 --- The de-coupling of soma and axons at system level --- p.34 / Chapter 1.6.3.4 --- Effects of DBS on abnormal rate or pattern --- p.35 / Chapter 1.6.3.5 --- Antidromic propagation of DBS effect towards cortex --- p.37 / Chapter 1.7 --- Objective --- p.38 / Chapter 1.8 --- Figures --- p.41 / CHAPTER 2 --- p.47 / General Methods --- p.47 / Chapter 2.1 --- Animals --- p.47 / Chapter 2.2 --- Stereotaxic surgery --- p.47 / Chapter 2.2.1 --- Preoperative preparation --- p.47 / Chapter 2.2.2 --- Anesthesia and craniotomy --- p.48 / Chapter 2.2.3 --- Induction of hemi-Parkinsonian rat model --- p.48 / Chapter 2.2.4 --- Electrode implantation techniques. --- p.49 / Chapter 2.3 --- Behavioral assessment. --- p.50 / Chapter 2.3.1 --- Apomorphine-induced contralateral rotation. --- p.50 / Chapter 2.3.2 --- Open field test --- p.50 / Chapter 2.4 --- STN-DBS protocol --- p.50 / Chapter 2.5 --- Electrophysiological data acquisition --- p.51 / Chapter 2.6 --- Data analysis --- p.52 / Chapter 2.6.1 --- Statistical analysis of behavioral data --- p.52 / Chapter 2.6.2 --- Electrophysiological data --- p.52 / Chapter 2.6.2.1 --- Stimulation artifact removal --- p.52 / Chapter 2.6.2.2 --- Multi-unit spike sorting --- p.53 / Chapter 2.6.2.3 --- Electrophysiological identification of pyramidal neuron and interneuron. --- p.54 / Chapter 2.6.2.4 --- Identification of antidromic cortical activation --- p.54 / Chapter 2.6.2.5 --- Discharge pattern classification --- p.54 / Chapter 2.6.2.6 --- Synchrony level evaluation --- p.55 / Chapter 2.6.2.7 --- Oscillatory rhythm characterization --- p.55 / Chapter 2.6.2.8 --- Coherence Level Measurement --- p.56 / Chapter 2.7 --- Histological verification --- p.56 / Chapter 2.8 --- Figures --- p.58 / CHAPTER 3 --- p.60 / Alleviation of Parkinsonian Motor Symptoms during Deep Brain Stimulation in Hemi-Parkinsonian Rats --- p.60 / Chapter 3.1 --- Introduction --- p.60 / Chapter 3.2 --- Materials & Methods --- p.61 / Chapter 3.2.1 --- Animals --- p.61 / Chapter 3.2.2 --- Chemicals --- p.61 / Chapter 3.2.3 --- Equipment --- p.61 / Chapter 3.3 --- Results --- p.62 / Chapter 3.3.1 --- Time course of the Apomorphine induced rotation behavior --- p.62 / Chapter 3.3.2 --- Dose-dependence of the Apomorphine induced rotation --- p.62 / Chapter 3.3.3 --- Acute behavioral response to STN-DBS. --- p.63 / Chapter 3.3.4 --- The dependence of STN-DBS effect on stimulation paradigm. --- p.64 / Chapter 3.3.5 --- Acute effects of STN-DBS on APO induced rotation. --- p.64 / Chapter 3.3.6 --- Long-term effects of STN-DBS on APO induced rotation --- p.64 / Chapter 3.3.7 --- Histological confirmation of the stimulation electrodes localization --- p.65 / Chapter 3.3.8 --- Loss of DA neurons in the SNc --- p.65 / Chapter 3.3.9 --- Reductions of the DA axon terminals in the striatum --- p.65 / Chapter 3.3.10 --- Chronic STN-DBS failed to rescue nigrostsriatal and striatal DA --- p.66 / Chapter 3.4 --- Discussion --- p.66 / Chapter 3.4.1 --- Neurotoxic mechanism of 6-OHDA --- p.66 / Chapter 3.4.2 --- Time course of dopamine degeneration induced by 6-OHDA --- p.66 / Chapter 3.4.3 --- Failure in observing worsened motor symptoms during low frequency STN-DBS. --- p.67 / Chapter 3.4.4 --- Experimental DBS based on rat model: does it mimic human case? --- p.67 / Chapter 3.4.5 --- Technical issues about STN-DBS --- p.69 / Chapter 3.5 --- Figures --- p.72 / CHAPTER 4 --- p.82 / Direct involvement of the Corticofugal Neurons in Motor Cortex during Therapeutic Deep Brain Stimulation --- p.82 / Chapter 4.1 --- Introduction --- p.82 / Chapter 4.2 --- Materials --- p.83 / Chapter 4.2.1 --- Animals --- p.83 / Chapter 4.2.2 --- Chemicals --- p.83 / Chapter 4.2.3 --- Equipment --- p.83 / Chapter 4.3 --- Results --- p.84 / Chapter 4.3.1 --- Identification of CxFn based on antidromic effect --- p.84 / Chapter 4.3.2 --- Antidromic spikes frequency correlates with therapeutic effect of STN-DBS. --- p.84 / Chapter 4.3.3 --- Pathological changes of neuronal firing rate in MI --- p.85 / Chapter 4.3.4 --- Only high frequency STN-DBS normalizes neuronal firing rate in MI --- p.86 / Chapter 4.3.5 --- Pathological changes of neuronal discharge pattern in MI --- p.88 / Chapter 4.3.6 --- Pathological synchrony of MI neuronal population, especially during burst discharge --- p.89 / Chapter 4.3.7 --- High frequency STN-DBS successfully suppresses synchronized burst discharge in MI --- p.89 / Chapter 4.3.8 --- Pathological β-band oscillatory activity in MI-LFPs induced by 6-OHDA lesion --- p.90 / Chapter 4.3.9 --- High frequency STN-DBS alleviates the β-band oscillation in MI-LFPs --- p.90 / Chapter 4.3.10 --- Synchronized bursting discharge correlates with oscillatory activity --- p.91 / Chapter 4.3.11 --- Pathological increased spike-LFP coherence level induced by 6-OHDA lesion --- p.92 / Chapter 4.3.12 --- High frequency STN-DBS modulated the spike-LFP coherence properties --- p.92 / Chapter 4.3.13 --- Antidromic spikes directly modulate the firing probability of CxFn --- p.93 / Chapter 4.3.14 --- Antidromic spikes modulate the firing probability of INs and non-CxFn nearby. --- p.94 / Chapter 4.3.15 --- The efficiency of antidromic cortical modulation depends on DBS frequency --- p.94 / Chapter 4.3.16 --- Orthodromic vs. antidromic effect: which one is responsible for the beneficial effect of DBS? --- p.95 / Chapter 4.3.17 --- Histology --- p.96 / Chapter 4.4 --- Discussion --- p.96 / Chapter 4.4.1 --- Origin of pathogenic rhythm in basal ganglia circuit --- p.96 / Chapter 4.4.2 --- Suppression of oscillatory synchronization equals to therapeutic effects of DBS? --- p.97 / Chapter 4.4.3 --- Beneficial effect of DBS corresponds to the topographic distribution of cortico-subthalamic projection. --- p.98 / Chapter 4.4.4 --- What is the reason for a stochastic pattern of antidromic activation effect? --- p.99 / Chapter 4.4.5 --- Desynchronization of pathological oscillatory rhythm by antidromic activation --- p.100 / Chapter 4.4.6 --- Antidromic vs. orthodromic: which is the cause of the beneficial effects of DBS? --- p.101 / Chapter 4.4.7 --- Wide propagation of antidromic effect by cortical horizontal circuits --- p.102 / Chapter 4.4.8 --- Significance of antidromic cortical activation in during STN-DBS --- p.102 / Chapter 4.4.9 --- Implication of antidromic activation effect on pathogenesis and treatment of PD --- p.104 / Chapter 4.5 --- Figures --- p.105 / CHAPTER 5 --- p.132 / Impaired Synaptic Plasticity in the Primary Motor Cortex after Dopamine Depletion: Potential Role in Motor Memory Consolidation --- p.132 / Chapter 5.1 --- Introduction --- p.132 / Chapter 5.1.1 --- Characteristics of motor learning --- p.132 / Chapter 5.1.2 --- Motor learning related cortical plasticity. --- p.133 / Chapter 5.1.3 --- Dopaminergic signals in the primary motor cortex --- p.134 / Chapter 5.1.4 --- Impaired cortical plasticity in PD --- p.135 / Chapter 5.1.5 --- Objective --- p.136 / Chapter 5.2 --- Materials --- p.136 / Chapter 5.2.1 --- Animals --- p.136 / Chapter 5.2.2 --- Chemicals --- p.136 / Chapter 5.2.3 --- Equipment --- p.136 / Chapter 5.3 --- Methods --- p.136 / Chapter 5.3.1 --- Functional mapping of the forelimb territory in MI --- p.136 / Chapter 5.3.2 --- Stereotaxic surgery --- p.137 / Chapter 5.3.3 --- Forelimb-reaching Task. --- p.137 / Chapter 5.3.4 --- In-vivo LTP Induction. --- p.138 / Chapter 5.4 --- Results --- p.139 / Chapter 5.4.1 --- Functional mapping of rat forelimb territory. --- p.139 / Chapter 5.4.2 --- Morphologies of evoked field potential response --- p.139 / Chapter 5.4.3 --- LTP of the early, monosynaptic plasticity within horizontal layer V MI --- p.140 / Chapter 5.4.4 --- LTP of the late, polysynaptic plasticity within horizontal layer V MI --- p.140 / Chapter 5.4.5 --- Impaired synaptic plasticity in MI after dopamine depletion --- p.140 / Chapter 5.4.6 --- Learning curve of forelimb-reaching task --- p.140 / Chapter 5.4.7 --- Physiologically enhanced cortical plasticity during motor learning --- p.141 / Chapter 5.4.8 --- Dynamic modulation of cortical neuronal activities during motor skill learning. --- p.142 / Chapter 5.4.9 --- Statistical analysis of ‘task related’ neuron’s modulation pattern. --- p.143 / Chapter 5.4.10 --- Loss of dopamine modulation in the MI --- p.144 / Chapter 5.5 --- Discussion --- p.144 / Chapter 5.5.1 --- Distinguishing between monosynaptic and polysynaptic transmission --- p.144 / Chapter 5.5.2 --- Artificially vs physiologically induced cortical plasticity. --- p.145 / Chapter 5.5.3 --- Cortical synaptic plasticity interprets motor learning dynamics --- p.146 / Chapter 5.5.4 --- Balance between neuronal recruitment and withdrawal in the consolidation stage --- p.147 / Chapter 5.5.5 --- Dopamine’s involvement in mediating the cortical synaptic plasticity. --- p.148 / Chapter 5.6 --- Figures --- p.150 / Conclusion --- p.162 / Abbreviations --- p.165 / References --- p.168

Introdução: A doença de Parkinson (DP) é uma doença neurodegenerativa cujo quadro clínico é essencialmente motor, no entanto as manifestações não motoras frequentemente estão presentes e muitas vezes são negligenciadas. Dentre as manifestações não motoras o declínio cognitivo tem ganhado destaque sendo causa de maior morbidade e mortalidade. A prevalência da demência na doença de Parkinson (DDP) varia de acordo com a população estudada e no momento do diagnóstico até 20% dos pacientes já apresentam algum grau de declínio cognitivo e com a evolução da doença até 80% dos pacientes apresentaram um quadro demencial associado a DP. Como A DP apresenta características clinico e patológicas sobrepostas à Doença de Alzheimer (DA) e a Apolipoproteína (ApoE) é o principal preditor de risco para desenvolvimento de demência na DA aventou-se a hipótese de que o alelo ?4 da ApoE pudesse ter relação com o risco de o paciente com DP desenvolver quadro demencial. Objetivo: analisar a relação entre o polimorfismo do gene ApoE com o desempenho cognitivo, avaliado pela MoCA, de pacientes com doença de Parkinson e descrever prevalência de cada alelo do gene em uma amostra de pacientes com DP da população brasileira. Método: estudo transversal onde foram analisados 186 pacientes em seguimento nos ambulatórios especializados em Distúrbios do Movimento do Hospital das Clínicas de Ribeirão Preto - HCFMRP e do Hospital São Paulo da Universidade Federal de São Paulo - UNIFESP, no período entre os anos de 2007 e 2014. Foi realizada a genotipagem dos alelos da ApoE e a avaliação cognitiva foi realiza através do MoCA. Para análise da amostra os pacientes foram classificados em portadores ou não do alelo ?4. Os grupos foram comparados utilizando o teste do Qui-quadrado para a variável sexo e o teste nãoparamétrico de Mann-Whitney para idade, tempo de doença e anos de estudo. Resultados: A análise dos escores da MoCA nos grupos com e sem o alelo ?4 não revelou diferença estatisticamente significativa entre os grupos (p=0,20). A frequência genotípica foi semelhante à descrita nos demais estudos sobre o assunto. Conclusão: a presença do alelo ?4 não está associada, em nossa amostra, a um pior desempenho cognitivo, quando este é avaliado pela escala cognitiva global MoCA. / Introduction: The Parkinson\'s disease (DP) is a neurodegenerative disorder where clinical findings are primarily motor however non-motor manifestations are often present and are frequently neglected. Among the non-motor events cognitive decline has gained prominence because it is cause of increased morbidity and mortality. The prevalence of Parkinson\'s disease dementia (PDD) varies depending on the population studied but at the time of diagnosis about 20% of patients already have some degree of cognitive decline and the progression of the disease up to 80% of patients demonstrated PDD. As DP has overlapping clinical and pathological features with Alzheimer\'s disease (DA) and apolipoprotein (ApoE) is the main predictor of risk for developing dementia in AD the hypothesis has suggested that the allele ?4 of ApoE could be related to the risk of the patient with PD develop dementia. Objective: analyze the relationship between ApoE gene polymorphism with the cognitive performance of patients with Parkinson\'s disease and describe prevalence of each allele of the gene in a sample of with PD in a Brazilian population. Method: cross-sectional study which analyzed 186 patients in follow-up in specialized of Hospital das Clínicas de Ribeirão Preto - HCFMRP and Hospital São Paulo of Universidade Federal de São Paulo - UNIFESP, between the years 2007 and 2014. Was made the genotyping for assessing the ApoE allele and cognitive assessment was carried out through the MoCA. For sample analysis, patients were classified as carriers or not allele ?4. The groups were compared using the chi-square test for gender and non-parametric Mann-Whitney test for age, disease duration and years of study. Results: The analysis of MoCA scores in the groups with and without the ?4 allele revealed no statistically significant difference between groups (p = 0.20). The genotypic frequency was similar to that described in other studies