INTRODUÇÃO: A doença de Parkinson é causada pela perda significativa de neurônios dopaminérgicos na substância nigra e perda celular no locus cerúleo, com perda do neurotransmissor dopamina e continuada deposição de inclusões proteicas nos tecidos cerebrais. A doença tem progressão caudo-rostral, iniciando-se no núcleo dorsal do nervo vago e, em grau menor, nos sistema olfativo, com evolução para o mesencéfalo e posteriormente para o prosencéfalo e neocórtex. Cerca de 90% dos casos são idiopáticos e o principal fator de risco é o envelhecimento. Para se compreender a interação genoma-ambiente e o mecanismo molecular nessa doença têm sido conduzidas investigações dos perfis de expressão gênica global em diversos tecidos-alvo. Essa abordagem de genômica funcional utiliza a tecnologia de DNA microarrays para estudo da expressão gênica e ferramentas de bioinformática para análise dos dados gerados. Neste trabalho foi feita uma análise das redes de interação transcricional em tecidos-alvo da doença de Parkinson utilizando-se amostras post mortem de tecidos cerebrais obtidas de pacientes e controles livres da doença. MÉTODOS: Estudo comparativo das redes de interação transcricional no núcleo dorsal do nervo vago, locus cerúleo e substância nigra entre pacientes com doença de Parkinson idiopática nos estágios Braak 4-5 e controles livres da doença utilizando material de necropsia. Foram utilizados DNA microarrays Agilent de 44 K e a análise estatística comparativa de dos transcritos válidos (TMEV) foi feita no vetor paciente X controle para cada região anatômica sob estudo. Para a análise das redes de interação transcricional dos grupos de pacientes e controles em cada região anatômica utilizou-se o software FunNet e as anotações genômicas do Gene Ontology Consortium. RESULTADOS: Os genes com maior número de ligações gene-gene em cada rede transcricional, ou hubs, foram identificados e correlacionados com sua função biológica e possível papel na doença de Parkinson. A análise comparativa entre o perfil de hubs (número de ligações, posição na rede) em cada região anatômica para pacientes e controles revelou que: i) no núcleo dorsal do nervo vago os hubs principais nas redes de controles e pacientes estão relacionados a funções de manutenção da homeostase cerebral e organização neuronal, ii) no locus cerúleo os hubs principais dos controles são genes ligados à manutenção das funções cerebrais, mobilização de células progenitoras (pericitos) e controle de vias inflamatórias, enquanto que na rede de pacientes esses hubs estão ligados aos processos de endo e exocitose, desenvolvimento neuronal e controle do estresse oxidativo e degradação de proteínas; iii) finalmente, na substância nigra os principais hubs da rede de controles estão envolvidos na proteção contra estresse oxidativo e proteínas não dobradas e na manutenção do sistema dopaminérgico mesodiencefálico, enquanto que na rede de pacientes predominam hubs ligados a processos epigenéticos de envelhecimento mitocondrial, transporte vesicular, neurogênese, inflamação e morte neuronal. CONCLUSÕES: Os resultados da análise de redes de interação transcricional de pacientes e controles em diferentes regiões anatômicas são compatíveis com o modelo de progressão caudo-rostral da doença de Parkinson e apontam para mecanismos compensatórios no núcleo dorsal do nervo vago e locus cerúleo / INTRODUCTION: Parkinson\'s disease is caused by a substantial loss of dopaminergic neurons in the substantia nigra and cell loss in locus coeruleus, concomitant loss of dopamine neurotransmitter and continuing deposition of protein within the brain as intracellular inclusions. The disease has a caudal-rostral progression, beginning in the dorsal nucleus of vagus nerve and, in a less extent, in the olfactory system, progressing to the midbrain and finally to the basal forebrain and the neocortex. About 90% of the cases are idiopathic and the main risk factor is ageing. In order to have a better understanding of the genome-environment interactions and of the molecular mechanisms involved in this disease, the investigation of global gene expression in different target tissues has been conducted. This functional genomic approach is based on DNA microarray technology and on the use of bioinformatics for analyzing the data. In the present work an analysis of transcriptional interaction networks in Parkinson\'s disease target tissues was conducted in post mortem cerebral tissue samples obtained from patients and disease-free controls. METHODS: Comparative study of transcriptional interaction networks in the dorsal nucleus of vagus nerve, locus coeruleus, and substantia nigra of idiopathic Parkinson\'s disease patients in Braak stages 4-5 and disease-free controls using post mortem tissue samples. Agilent 44 K DNA microarrays were used and the statistical comparative analysis of valid transcripts was accomplished (TMEV) in the vector patient X control for each anatomic region under study. In order to analyze the transcriptional interaction networks for patient and control groups in each anatomic region the FunNet software and the Gene Ontology genomic annotations were used. RESULTS: The genes with high number of gene-gene connections in each transcriptional network, or hubs, were identified and related to their biological function and putative role in Parkinson\'s disease. The comparative analysis between hub profiles (number of connections, position in the network) in each anatomic region for patients and controls revealed that: i) in the dorsal nucleus of vagus nerve the main hubs in patient and control networks are related to the maintenance of brain homeostasis and to neuronal organization; ii) in the locus coeruleus the main hubs of control network are related to the maintenance of brain functions, mobilization of progenitor cells (pericytes) and control of inflammatory pathways, whereas in the patient network the main hubs are linked to exo and endocytosis processes, neuronal development and control of oxidative stress and protein degradation; iii) finally, in the substantia nigra the main hubs in the control network are related to protection against oxidative stress and unfolded/misfolded proteins and in the maintenance of the midbrain dopaminergic system, whereas in the patient network the main hubs are related to epigenetic processes of mitochondrial ageing, vesicular transport, neurogenesis and inflammation and neuronal death. DISCUSSION: The results of transcriptional interaction networks analyses performed for patient and control groups in different anatomic regions are compatible with the caudal-rostral model of Parkinson\'s disease progression and point out to compensatory mechanisms acting in vagus nerve and locus coeruleus

Les neurones noradrénergiques (NA) du locus coeruleus (LC) et sérotoninergiques (5-HT) du noyau du raphé dorsal (NRD) sont fortement impliqués dans la régulation des états d'éveil et de sommeils. Ces neurones ont, au cours de l'éveil, une activité spontanée tonique régulière qui diminue progressivement au cours du sommeil lent (SL) et cesse au cours du sommeil paradoxal (SP) (neurones "SP-OFF"). La diminution puis l'arrêt d'activité des neurones NA et 5-HT seraient une condition nécessaire à l'endormissement et à la survenue du SP. Les mécanismes à l'origine de cette modulation d'activité des neurones NA et 5-HT au cours du cycle veille-sommeil demeurent toutefois inexpliqués.<br /><br />Sur la base de données anatomiques et électrophysiologiques, il a été suggéré que la diminution puis la cessation d'activité des neurones NA du LC et 5-HT du NRD au cours du SL et du SP seraient dues (1) à une dé-activation consécutive à l'arrêt d'entrées synaptiques excitatrices, (2) à des mécanismes d'auto-inhibition, (3) à une action inhibitrice de l'adénosine, (4) à la mise en jeu d'afférences GABAergiques et/ou glycinergiques. <br />Afin de tester ces différentes hypothèses nous avons développé une approche électrophysio-logique et micropharmacologique sur un nouveau modèle expérimental de rat non anesthésié en contention stéréotaxique. Cette technique, non stressante, nous a permis de réaliser l'enregistrement extracellulaire unitaire des neurones NA et 5-HT au cours du cycle veille-sommeil, couplé à la micro-iontophorèse d'agonistes et d'antagonistes des différents neurotransmetteurs.<br /><br />Les résultats obtenus soutiennent l'hypothèse selon laquelle l'activité tonique des neurones NA du LC au cours de l'éveil serait sous la dépendance de leurs propriétés intrinsèques. L'activité des neurones 5-HT du NRD, en revanche, dépendrait au moins en partie de l'influence excitatrice des neurones NA. <br />Nous avons déterminé également que le GABA et la glycine exercent une influence inhibitrice tonique sur les neurones NA et 5-HT tout au long du cycle veille-sommeil. Nos résultats suggèrent en outre que le tonus inhibiteur glycinergique serait constant alors que le tonus GABAergique augmenterait progressivement au cours du SL et serait maximum au cours du SP. Le GABA serait ainsi le neurotransmetteur responsable de l'inactivation des neurones NA du LC et 5-HT du NRD nécessaire à l'endormissement et à la survenue au SP.<br /><br />Ces données soutiennent l'hypothèse selon laquelle deux populations de neurones GABAergiques seraient impliquées dans l'inactivation des neurones NA et 5-HT au cours du sommeil. L'une, localisée dans l'aire préoptique latérale et ventrolatérale serait mise en jeu au cours du SL, la seconde, localisée dans la substance grise péri-aqueducale, serait mise en jeu au cours du SP.

O gás monóxido de carbono (CO) possui diversas funções no sistema nervoso central (SNC) funcionando como neuromodulador, como por exemplo da regulação da temperatura corporal, da nocicepção e mais recentemente, do comportamento emocional. Este neuromodulador gasoso é produzido pela ação da enzima heme oxigenase (HO), a qual é encontrada em diferentes áreas do SNC. Com destaque, esta enzima tem alta expressão no locus coeruleus (LC), o que sugere o envolvimento do CO na modulação de funções desempenhadas por esta estrutura. O LC localiza-se na ponte, sendo a maior origem da inervação noradrenérgica do SNC. Esta estrutura tem participação ativa na modulação das respostas relacionadas ao estresse, em particular, na modulação do comportamento emocional, desde que integra o Sistema de Inibição Comportamental (SIC), o qual inclui ainda o sistema septo-hipocampal e os núcleos da rafe. O SIC é responsável por comandar respostas defensivas de avaliação de risco, alerta e atenção, as quais podem ser eliciadas pela ansiedade. Dentro desta perspectiva, o presente estudo teve como objetivo avaliar se a ativação sistêmica da via HO-CO pode modular o comportamento emocional de ratos, e se há participação do LC. Assim, este trabalho avaliou se o tratamento sistêmico via intraperitoneal (i.p.) agudo (3 h antes) ou crônico (10 dias/2 vezes ao dia) com um liberador de monóxido de carbono (CORM-2), ou com indutor da enzima HO (CoPP), altera as respostas comportamentais no teste do labirinto em cruz elevado (LCE) e no teste claro-escuro (TCE) em ratos, bem como a expressão da enzima HO no LC. Em uma segunda etapa foi avaliado se a administração aguda de CORM-2 ou CoPP altera o comportamento avaliado no LCE e no TCE de ratos submetidos ao estresse crônico variado (ECV) por 10 dias. Os resultados mostraram que o CO induzido pela administração aguda ou crônica de CORM-2 ou CoPP possui efeito ansiolítico. Ainda, o tratamento com CORM-2 ou CoPP aumentou a expressão da enzima HO-1 em células localizadas no LC, sem alterar a imunorreatividade à enzima HO-2. Considerando os grupos submetidos ao estresse ECV, nem a ativação da via HO-CO ou o ECV apresentaram efeitos significativos nos comportamentos avaliados nos testes LCE e TCE. Os resultados do presente estudo sugerem que o tratamento sistêmico com drogas que modulam a liberação de CO possui claro efeito ansiolítico. Assim, é possível que o CO possa ser uma droga com potencial terapêutico para o tratamento de desordens neuropsiquiátricas. / The carbon monoxide gas (CO) has several functions in the central nervous system acting as a neuromodulator, such as in the body temperature regulation, nociception and more recently, in the emotional behavior modulation. This gas is produced by the action of the heme oxigenase enzyme (HO), which is found in different areas of the central nervous system (CNS). It is important to note that this enzyme has high expression in the locus coeruleus (LC), suggesting the involvement of CO in the modulation functions performed by this midbrain structure. LC is located in the pons, being the source of majority of the noradrenergic innervation of the CNS. This structure is intimately involved in the stress modulation responses, particularly in the emotional behavior regulation, since it integrates the Behavioral Inhibition System (BIS), which also includes septum-hippocampal system and raphe nucleus. The BIS is responsible for defensive responses like the risk assessment and alertness trigged by anxiety. Within this perspective, the present study was designed to evaluate whether the systemic HO-CO pathway can modulate emotional behavior of rats, and if the HO enzyme of the neurons located into LC is involved in this response. Thus, this study evaluated whether the acute systemic i.p. treatment (3 hours before) or chronic (10 days / 2 times a day) with a carbon monoxide releaser (CORM-2) or inducer of heme enzyme oxygenase (CoPP), is able to alter the behavioral responses in the elevated plus maze (EPM) and in the light-dark box test (LDB) in rats, and the HO enzyme expression in the LC. Furthermore, the effect of the acute administration of CORM-2 or CoPP was evaluated in the emotional behavior assessed in the EPM and LDB by rats submitted to unpredictable chronic stress (during 10 days). The results showed that the CO induced by acute or chronic administration of CORM-2 or CoPP has an anxiolytic-like effect. Furthermore, treatment with CORM-2 or CoPP promoted an increase of HO-1 enzyme expression in cells located in the LC without altering the immunoreactivity of HO-2 enzyme. Still, considering the rats subjected to stress UCS neither the activation of HO-CO pathway nor the UCS protocol altered the emotional behavior evaluated in the EPM and LDB tests. The results of this study suggest that systemic treatment with drugs that modulate the CO release has anxiolytic effect. Thus, it is possible that CO can be a potential drug therapeutic target for neuropsychiatric disorders.

Alzheimer’s disease (AD) is a degenerative disorder where the distribution of pathology throughout the brain is not random but follows a predictive pattern used for pathological staging. While the involvement of defined functional systems is fairly well established for more advanced stages, the initial sites of degeneration are still ill defined. The prevailing concept suggests an origin within the transentorhinal and entorhinal cortex (EC) from where pathology spreads to other areas. Still, this concept has been challenged recently suggesting a potential origin of degeneration in nonthalamic subcortical nuclei giving rise to cortical innervation such as locus coeruleus (LC) and nucleus basalis of Meynert (NbM). To contribute to the identification of the early site of degeneration, here, we address the question whether cortical or subcortical degeneration occurs more early and develops more quickly during progression of AD. To this end, we stereologically assesses neurone counts in the NbM, LC and EC layer-II in the same AD patients ranging from preclinical stages to severe dementia. In all three areas, neurone loss becomes detectable already at preclinical stages and is clearly manifest at prodromal AD/MCI. At more advanced AD, cell loss is most pronounced in the NbM > LC > layer-II EC. During early AD, however, the extent of cell loss is fairly balanced between all three areas without clear indications for a preference of one area. We can thus not rule out that there is more than one way of spreading from its site of origin or that degeneration even occurs independently at several sites in parallel.

No description available.

Vagus nerve stimulation (VNS) is a promising neuromodulatory therapy under investigation for a range of disorders, including heart failure, gastric dysmotility, and migraine. Two primary forms of VNS are currently investigated: cervical VNS (cVNS), involving surgically implantation to activate vagal afferents in the cervical branch in the neck and transcutaneous auricular VNS (taVNS) which subcutaneously stimulates the auricular branch in the outer ear. The nucleus of the solitary tract (NTS) serves as a relay-station receiving 90% of vagal afferents, enabling connections with higher-order brain regions and other brainstem nuclei like the spinal trigeminal nucleus (Sp5) and locus coeruleus (LC), facilitating neuromodulation through VNS. Research has established the efficacy of VNS at 20–30 Hz for disorders like depression, but the impact of alternative stimulation parameters on medullary nuclei neuromodulation remains unclear. These studies used anesthetized rats to extracellularly record neuronal activity across varying VNS parameters within NTS, Sp5, and LC. Neuronal responses were classified as positive (increased activity), negative (decreased activity), or non-responders (no response). In LC, cVNS at standard paradigms (≥ 10 Hz) and bursting paradigms with shorter interburst intervals or increased pulses induced more positive responders, while standard 5 Hz generated more negative responders. Additionally, a build-up effect was observed in LC, with increased responders over consecutive VNS cycles. In NTS and Sp5, taVNS evoked comparable activation, with more positive responders at 20 Hz and 100 Hz and stronger responses at higher intensities. However, Sp5 responses were twice as strong compared to NTS. Furthermore, comparative analysis between taVNS and cVNS revealed similar overall activation in NTS, but distinct activation profiles in individual neurons indicate different pathways. Finally, the therapeutic efficacy of VNS therapy was evaluated in heart failure using a pressure-overload rat model. A 60-day cVNS treatment restored adverse cardiac remodeling and dysfunction, mitigated cardiac molecular changes, and prevented neuroinflammatory responses within brainstem nuclei. The findings presented herein demonstrated differential parameter-specific and nuclei-specific responses to taVNS and cVNS, investigated the mechanisms responsible for taVNS modulation, and confirmed that VNS therapy, when initiated early, can mitigate heart failure development and restore multiorgan homeostasis in a PO model.

No / The molecular identity of ion channels which confer PCO(2)/pH sensitivity in the brain is unclear. Heteromeric Kir4.1/Kir5.1 channels are highly sensitive to inhibition by intracellular pH and are widely expressed in several brainstem nuclei involved in cardiorespiratory control, including the locus coeruleus. This has therefore led to a proposed role for these channels in neuronal CO(2) chemosensitivity. To examine this, we generated mutant mice lacking the Kir5.1 (Kcnj16) gene. We show that although locus coeruleus neurons from Kcnj16((+/+)) mice rapidly respond to cytoplasmic alkalinization and acidification, those from Kcnj16((-/-)) mice display a dramatically reduced and delayed response. These results identify Kir5.1 as an important determinant of PCO(2)/pH sensitivity in locus coeruleus neurons and suggest that Kir5.1 may be involved in the response to hypercapnic acidosis.

The process of respiration is a pattern of spontaneity and automatic motor control that originate in the brainstem. The mechanism by which the brainstem detects CO2 is termed central CO2 chemoreception (CCR). Since the early 1960’s there have been tremendous efforts placed on identification of central CO2 chemoreceptors (molecules that detect CO2). Even with these efforts, what a central CO2 chemoreceptor looks like remain unknown. To test the hypothesis that inward rectifier K+ (Kir) channels are CO2 sensing molecules in CCR, a series of experiments were carried out. 1) The first question asked was whether the Kir4.1-Kir5.1 channel is expressed in brainstem chemosensitive nuclei. Immunocytochemistry was performed on transverse medullary and pontine sections using antibodies raised against Kir4.1 and Kir5.1. Positive immunoassays for both Kir4.1 and Kir5.1 subunits were found in CO2 chemosensitive neurons. In the LC the Kir4.1 and Kir5.1 were co-expressed with the neurokinin-1 receptor that is the natural receptor for substance P. 2) The second question asked was whether the Kir4.1-Kir5.1 channel is subject to modulation by neurotransmitters critical for respiratory control. My studies demonstrated that indeed the Kir4.1-Kir5.1 channel is subject to modulation by substance P, serotonin and thyrotropin releasing hormone. 3) I performed studies to demonstrate the intracellular signaling system underlying the Kir4.1-Kir5.1 channel modulation by these neurotransmitters. The modulation by all three neurotransmitters was dependent upon the activation of protein kinase C (PKC). The Kir4.1-Kir5.1 but not the Kir4.1 channel was modulated by PKC. Both the Kir4.1 and Kir5.1 subunits can be phosphorylated by PKC in vitro. However, systematic mutational analysis failed to reveal the phosphorylation site. 4) The fourth question asked was whether Kir channels share a common pH gating mechanism that can be identified. Experiments were performed to understand the gating of the Kir6.2+SUR1 channel as specific sites for ligand binding and gating have been demonstrated. I identified a functional gate that was shared by multiple ligands that is Phe168 in the Kir6.2. Other Kir channels appear to share a similar gating mechanism. Taken together, these studies demonstrate the modulation of Kir channels in central CO2 chemoreception.

A recent model of Parkinson’s disease (PD) suggests that the neuropathological, behavioural and cognitive symptoms progress in stages. There is substantial evidence for a prodromal stage of PD, during which time pre-motor symptoms develop. Rapid eye movement (REM) sleep behaviour disorder (RBD) is a risk factor for developing PD and may be part of the pre-motor stage. In both disorders, neuropathological α-synuclein aggregates are thought to be a direct cause of the resulting symptoms. One model has shown that in rats, proteasome inhibition produced by systemic exposure to environmental toxins results in α-synuclein pathology and motor behaviour dysfunction that mimics the progression of PD in humans. The present study examined the hypothesis that the systemic proteasome inhibition model would produce pre-Parkinsonian RBD-like pathology in rats. It was expected that sleep disturbances would be seen prior to behavioural disturbances in rats treated systemically with PSI (a proteasome inhibitor). Following baseline sleep recording and training on the inclined beam-traverse task, rats were injected with PSI (a proteasome inhibitor) or ethanol (control), 6 times over 2 wk. Sleep recording over 8 wk and behavioural testing over 16 wk provided no evidence of sleep disturbances or motor dysfunction. Post-mortem immunohistochemical analyses of brain tissue provided no evidence of PSI-associated α-synuclein aggregates in the locus coeruleus, subcoeruleus (dorsal part), or substantia nigra (areas involved in RBD and/or PD). These results did not provide support for RBD as a prodromal phase of PD within the systemic proteasome inhibitor-based model and add to a growing body of research reporting inconsistent findings using this model. We suggest that systemic PSI exposure in rats does not produce a viable model of RBD or PD. Whether RBD is an early symptom in the progression of PD remains to be established. / Thesis (Master, Neuroscience Studies) -- Queen's University, 2010-04-28 12:04:50.613

No description available.