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Connecting the brain to the spinal cord, the brain stem Brainstem (BST) is an area of convergence of motor and sensory pathways. It has different nuclei, responsible for various functions such as motor skills, regulation of respiratory and cardiac rhythms, the origin of cranial nerves. Despite its importance in various neurodegenerative diseases, in vivo exploration of BST is still a challenge today. The resolution used, the low contrast and its location make it difficult to study in conventional magnetic resonance imaging (MRI). Based on various advanced MRI sequences, we carried out a study of the substantia nigra (SN) in a population of Parkinson's patients, an area located in the upper part of the BST. The results show that iron imaging combined with free water imaging suggests different underlying pathophysiological processes. Nevertheless, given the size of the structures studied, the need for precision remains necessary for more reliable identification. The originality of the proposal is to develop a method dedicated to BST, in order to best overcome the difficulties of its observation. By optimizing MRI acquisitions and several image processing, the results obtained show the possibility of easily identifying certain structures and stabilizing quantitative values. To conclude, still with the objective of improving MRI measurements, we were interested in MRI on human anatomical parts. Post-mortem MRI is used in this thesis for the detection and quantification of metals (iron) and correlation with histological techniques.; Reliant le cerveau à la moelle épinière, le tronc cérébral (TC) est une zone de convergence des voies motrices et sensitives. Il comporte différents noyaux, responsables de diverses fonctions comme la motricité, la régulation des rythmes respiratoires et cardiaques, l'origine de nerfs crâniens. Malgré une importance dans différentes pathologies neurodégénératives, l'exploration in vivo du TC reste encore aujourd'hui un enjeu à relever. La résolution employée, le faible contraste et sa localisation rendent son étude difficile en imagerie par résonance magnétique (IRM) conventionnelle. A partir de différentes séquences IRM avancées, nous avons réalisé, chez une population de patients parkinsoniens, une étude de la substance noire (SN), zone située dans la partie haute du TC. Les résultats montrent que l'imagerie du fer associée à l'imagerie de l'eau libre suggère des processus physiopathologiques sous-jacents différents. Néanmoins, aux vues de la taille des structures étudiées, le besoin de précision reste nécessaire pour une identification avec plus de fiabilité. L'originalité de la proposition est de développer une méthode dédiée au TC, afin de pallier au mieux, les difficultés de son observation. Par une optimisation des acquisitions IRM, et plusieurs traitements d'images, les résultats obtenus montrent la possibilité d'identifier facilement certaines structures et une stabilisation des valeurs quantitatives. Pour terminer, toujours dans l'objectif de l'amélioration des mesures IRM, nous nous sommes intéressés à l'IRM sur pièces anatomiques humaines. L'IRM post-mortem est utilisé dans le cadre de cette thèse pour la mise en évidence et la quantification des métaux (fer) et la corrélation avec des techniques histologiques.

Multiple system atrophy (MSA) is a rapidly progressing orphan disease characterized by neurodegeneration in several brain regions, including olivopontocerebellar and striatonigral systems, together with several brainstem autonomic nuclei. The hallmark of MSA is the presence of oligodendroglial aggregates named glial cytoplasmic inclusions, which are mostly composed of the protein α-synuclein (α-syn). The neurodegenerative process causes a variable combination of parkinsonism, cerebellar impairment and autonomic dysfunction. No disease modifying therapies, nor peripheral biomarkers that would allow detecting or monitoring the evolution of MSA, are yet available. My PhD work was a multifactorial approach which allowed me to work on the different levels of therapeutic research, from animal modelling to preclinical research, and finally the search for fluid biomarkers in patient samples. We first created new models of MSA based on viral-mediated overexpression of α-syn in striatal oligodendrocytes in rats and non-human primates. We showed in our rat model progressive motor dysfunction, degeneration of dopaminergic neurons of the substantia nigra pars compacta (SNc) and striatal neurons, as well as pathological aggregation of α-syn. For the primate model, we established the specificity of oligodendroglial α-syn expression and the reach of the viral infection. In the second part, we studied the effect of three therapeutic strategies on neurodegeneration and α-syn aggregation in a transgenic murine model of MSA. Rapamycine, known to activate protein degradation through autophagy, showed a partial neuroprotective effect on dopaminergic neurons of the SNc, while intraperitoneal administration of nilotinib, which exerted neuroprotective and anti-aggregative effects in several models of Parkinson’s disease, failed to show any effect in transgenic MSA mice. The last therapeutic strategy aimed to act on brain insulin resistance, which is one of the pathological features found in MSA patient brains, through viral-mediated overexpression of a micro RNA that reduces the expression of the G protein (heterotrimeric guanine nucleotide–binding protein)–coupled receptor kinase 2 (GRK2). The inhibition of the GRK2 kinase, which is involved in mediating insulin resistance, showed neuroprotective effects in the SNc in transgenic MSA mice. The third project of my PhD work consisted in the assessment of several potential fluid biomarkers in MSA patients using the SIMOA technology., L’atrophie multisystématisée (AMS) est une maladie neurodégénérative orpheline altérant de nombreuses régions du système nerveux central, notamment les systèmes olivopontocérébelleux et striatonigral ainsi que divers noyaux autonomes du tronc cérébral, et dont la progression est très rapide. La principale caractéristique de l’AMS est la présence d’agrégats oligodendrogliaux nommés inclusions cytoplasmiques gliales dont le principal composant est la protéine α-synucléine (α-syn). La dégénérescence entraine notamment une grave atteinte des fonctions autonomes, ainsi qu’à un degré variable un syndrome parkinsonien et des troubles cérébelleux. Il n’existe aujourd’hui aucun traitement modifiant la progression de la maladie ni de biomarqueur permettant de détecter ou de suivre son évolution. Ma thèse est une approche multifactorielle qui m’a permis de travailler sur les diverses étapes de la recherche à visée thérapeutique, de la modélisation animale à la phase pré-clinique, puis à la détermination de potentiels biomarqueurs de la sévérité de la maladie. Dans la première partie de la thèse, nous avons induit une surexpression virale de l’α-syn oligodendrogliale par injection stéréotaxique striatale chez le rat et le singe. Nous avons montré chez le rat une dysfonction motrice progressive, une dégénérescence des neurones dopaminergiques de la substance noire compacte (SNc) mais aussi des neurones striataux, ainsi qu’une agrégation pathologique de l’α-syn. Pour le modèle primate, nous avons déterminé la spécificité de l’expression de l’α-syn oligodendrogliale, l’étendue de l’infection virale et de la présence de l’α-syn. Dans un second temps, nous avons étudiés l’effet de trois stratégies thérapeutiques sur la neurodégénérescence et l’agrégation de l’α-syn retrouvées dans un modèle murin transgénique de l’AMS. La rapamycine, dont une des actions est d’activer la dégradation protéique, a montré un effet neuroprotecteur partiel sur la dégénérescence des neurones de la SNc, tandis que l’administration intrapéritonéale du nilotinib qui avait montré des effets neuroprotecteurs et anti agrégatifs dans divers modèles de la maladie de Parkinson n’a eu aucun effet dans ce modèle. La troisième stratégie thérapeutique a pour but d’agir sur la résistance à l’insuline cérébrale, qui est une des caractéristiques des patients AMS, chez notre modèle murin transgénique par une approche d’injection stéréotaxique virale au niveau du striatum induisant la surexpression d’un micro ARN. L’inhibition de la kinase GRK2, impliquée dans les phénomènes de résistance à l’insuline, suite à cette injection a montré des effets neuroprotecteurs dans la SNc. Le troisième projet de ma thèse a consisté à mesurer, grâce à la technologie SIMOA, la concentration de plusieurs biomarqueurs potentiels dans le sérum et le liquide céphalo rachidien de patients AMS et à les corréler avec les données cliniques.

Connecting the brain to the spinal cord, the brain stem Brainstem (BST) is an area of convergence of motor and sensory pathways. It has different nuclei, responsible for various functions such as motor skills, regulation of respiratory and cardiac rhythms, the origin of cranial nerves. Despite its importance in various neurodegenerative diseases, in vivo exploration of BST is still a challenge today. The resolution used, the low contrast and its location make it difficult to study in conventional magnetic resonance imaging (MRI). Based on various advanced MRI sequences, we carried out a study of the substantia nigra (SN) in a population of Parkinson's patients, an area located in the upper part of the BST. The results show that iron imaging combined with free water imaging suggests different underlying pathophysiological processes. Nevertheless, given the size of the structures studied, the need for precision remains necessary for more reliable identification. The originality of the proposal is to develop a method dedicated to BST, in order to best overcome the difficulties of its observation. By optimizing MRI acquisitions and several image processing, the results obtained show the possibility of easily identifying certain structures and stabilizing quantitative values. To conclude, still with the objective of improving MRI measurements, we were interested in MRI on human anatomical parts. Post-mortem MRI is used in this thesis for the detection and quantification of metals (iron) and correlation with histological techniques., Reliant le cerveau à la moelle épinière, le tronc cérébral (TC) est une zone de convergence des voies motrices et sensitives. Il comporte différents noyaux, responsables de diverses fonctions comme la motricité, la régulation des rythmes respiratoires et cardiaques, l'origine de nerfs crâniens. Malgré une importance dans différentes pathologies neurodégénératives, l'exploration in vivo du TC reste encore aujourd'hui un enjeu à relever. La résolution employée, le faible contraste et sa localisation rendent son étude difficile en imagerie par résonance magnétique (IRM) conventionnelle. A partir de différentes séquences IRM avancées, nous avons réalisé, chez une population de patients parkinsoniens, une étude de la substance noire (SN), zone située dans la partie haute du TC. Les résultats montrent que l'imagerie du fer associée à l'imagerie de l'eau libre suggère des processus physiopathologiques sous-jacents différents. Néanmoins, aux vues de la taille des structures étudiées, le besoin de précision reste nécessaire pour une identification avec plus de fiabilité. L'originalité de la proposition est de développer une méthode dédiée au TC, afin de pallier au mieux, les difficultés de son observation. Par une optimisation des acquisitions IRM, et plusieurs traitements d'images, les résultats obtenus montrent la possibilité d'identifier facilement certaines structures et une stabilisation des valeurs quantitatives. Pour terminer, toujours dans l'objectif de l'amélioration des mesures IRM, nous nous sommes intéressés à l'IRM sur pièces anatomiques humaines. L'IRM post-mortem est utilisé dans le cadre de cette thèse pour la mise en évidence et la quantification des métaux (fer) et la corrélation avec des techniques histologiques.

Les neurones dopaminergiques de la substance noire (SNc) sont les plus vulnérables à la dégénérescence dans la maladie de Parkinson et ses modèles animaux. Suite à des travaux antérieurs et à des résultats préliminaires du laboratoire Trudeau, notre hypothèse actuelle suggère que la très grande taille de l'arborisation axonale des neurones de la SNc soit un facteur clé à l'origine de leur vulnérabilité, puisque cet état devrait être associé à un taux élevé de phosphorylation oxydative et de production de radicaux libres. En accord avec cette hypothèse, les autres populations dopaminergiques, dotées d'arborisations de moindre taille, résistent mieux aux lésions expérimentales et à la maladie chez l'humain. L'objectif du présent projet était de développer un modèle murin dans lequel les neurones de la SNc présentent une taille d'arborisation axonale plus grande, se rapprochant davantage de celle observée chez l'humain et en reproduisant la vulnérabilité, ce qui pourrait représenter une percée importante dans l'identification de nouvelles approches thérapeutiques. Basée sur le bourgeonnement axonal compensatoire des neurones dopaminergiques suite à des lésions partielles, la méthode utilisée fut l'injection unilatérale intranigrale de la toxine 6-hydroxydopamine (6-OHDA) à quelques jours de vie (P5), en visant l'élimination de 50% des neurones de la SNc. Un immunomarquage contre la tyrosine hydroxylase (TH), enzyme de synthèse de la dopamine, ainsi qu'une quantification du signal TH dans le striatum et des comptes neuronaux stéréologiques ont permis de quantifier la lésion partielle et de mettre en évidence la présence d'une croissance axonale compensatoire des neurones dopaminergiques survivants, à 10 et 90 jours post-lésion, suggérant une compensation précoce. Afin de mettre en évidence l'origine du bourgeonnement axonal, nous avons injecté un vecteur viral de type AAV encodant une protéine fluorescente (EYFP) dans la SNc ou la VTA des animaux adultes. Nos résultats confirment la présence de neurones nigrostriés à plus grande arborisation suivant une lésion unilatérale précoce à la 6-OHDA, dont la vulnérabilité accrue pourra être évaluée dans des expériences à venir par des protocoles lésionnels au MPTP, une toxine permettant de modéliser la maladie de Parkinson chez la souris., Dopaminergic neurons of the substantia nigra (SNc) are amongst the most vulnerable to neurodegeneration in Parkinson's disease and its animal models. According to previous work and preliminary results in our laboratory, our present hypothesis postulates that the large axonal arborisation size of SNc neurons is a key driving factor in their vulnerability, since this characteristic is associated with increased oxidative phosphorylation levels and free radicals production. In agreement with this hypothesis, other dopaminergic populations with smaller axonal arbors better resist to experimental lesions and to the disease process in humans. The current project aims to develop a mouse model in which SNc neurons present an axonal arborisation of increased size, closer to what is encountered in humans, thus reproducing their vulnerability, which could represent an important breakthrough in the identification of new therapeutic approaches. Based on compensatory axonal sprouting of dopaminergic neurons following partial lesions, the method used was the unilateral intranigral injection of the toxin 6-hydroxydopamine (6-OHDA) at an early age (P5), to induce the loss of approximately 50% of SNc neurons. Immunostaining against tyrosine hydroxylase (TH), an enzyme required for the synthesis of dopamine, TH signal quantification in the striatum and stereological counting of neurons allowed for the quantification of the partial lesion and demonstrated compensatory axonal sprouting at 10 and 90 days post-lesion, with our results suggesting an early compensation. To better characterize the origin of axonal sprouting, we injected an AAV viral vector encoding a fluorescent protein (EYFP) in either the SNc or the VTA of adult animals. Our results confirm the presence of nigrostriatal neurons with increased arborisation sizes following early unilateral lesion using 6-OHDA, whose increased vulnerability will be evaluated in future experiments through lesion protocols using MPTP, a toxin used to model Parkinson's disease in mice.

This thesis work describes and analyzes the neuroinflammatory reaction that accompanies neuronal cell death in a murine model of Parkinson's disease. In this model, induced by the intrastriatal injection of 6-hydroxydopamine (6-OHDA), a toxic dopamine analog, we report on the main features and kinetics of microglial activation, T-cell infiltration, loss of TH+ (Tyrosine Hydroxylase) dopaminergic neurons and motor behavior alterations. We also assessed the presence of T-cells in the susbstantia nigra of Parkinson's disease patients and found that, as observed in the 6-OHDA murine model, the neuronal cell death of dopaminergic neurons triggers a low-grade T-cell infiltration that accompanies microglial activation. We then studied the impact of genetically-determined T-cell immunodeficiency on histological and functional outcomes in the 6-OHDA model. Our results show that, as compared to immunocompetent control mice, immunodeficient strains consisting in Foxn1 KO, CD3 KO, NOD SCID or RAG KO mice consistently presented, at varied levels, a highest susceptibility to 6-OHDA induced dopaminergic neurodegeneration. The observed accentuation of neuronal cell loss was accompanied by a marked increase of microglial activation and motor behavior alterations. Our work demonstrates the pathophysiological role of neuroinflammation and adaptative immunity in the 6-OHDA model. It also suggests that T-cells infiltrating the substantia nigra of Parkinson's disease patients dampen microglial activation and could, via this inhibitory effect, slow the progression of dopaminergic cell loss. Overall this thesis work provides original data on the interactions between T-cells, microglia and dopaminergic neurons in the context of Parkinson's disease and the murine 6-OHDA model, Ce travail de thèse décrit et analyse la réaction neuro-inflammatoire accompagnant la mort cellulaire neuronale dans un modèle murin de la maladie de Parkinson. Dans ce modèle, induit par l’injection intrastriatale d'un analogue toxique de la dopamine, la 6-hydroxydopamine (6-OHDA), nous décrivons les caractéristiques et la cinétique de l’activation microgliale, de l'infiltration lymphocytaire T, de la perte de neurones dopaminergiques TH+ (Tyrosine Hydroxylase) et des altérations du comportement moteur. Nos observations sont complétées par une étude neuropathologique de la substance noire chez des patients atteints de maladie de Parkinson. Les résultats montrent que, chez l'homme comme chez la souris, la mort de neurones dopaminergiques induit une infiltration T de faible intensité, limitée à la substance noire et s'accompagnant d'une activation microgliale. Dans un deuxième temps, nous analysons l'impact d'une déficience lymphocytaire T génétiquement déterminée sur les paramètres histologiques et fonctionnels caractérisant le modèle 6-OHDA. Nos résultats montrent que, comparées à des souris contrôles immunocompétentes, les souris immunodéficientes de souche Foxn1 KO, CD3 KO, NOD SCID ou RAG1 KO présentent toutes, à des degrés divers, une susceptibilité significativement accrue aux effets neurotoxiques de la 6-OHDA. L'aggravation observée de la perte neuronale s'accompagne d'une accentuation majeure des troubles du comportement moteur et de l'activation microgliale. Ce travail démontre l'importance de la neuro-inflammation et de l'immunité adaptative dans la physiopathologie du modèle 6-OHDA. Il suggère également que les LyT infiltrant la substance noire des patients atteints de maladie de Parkinson exercent un rôle inhibiteur sur l'activation microgliale et pourraient par ce mécanisme ralentir l'évolution de la perte neuronale dopaminergique. En résumé, ce travail de thèse apporte un ensemble de données originales sur les interactions entre LyT, microglie et neurones dopaminergiques dans le contexte de la maladie de Parkinson et du modèle murin 6-OHDA

Une sous-population des neurones à dopamine (DA) du mésencéphale ventral du rat et de la souris étant connue pour exprimer l'ARN messager du transporteur vésiculaire 2 du glutamate (VGLUT2), nous avons eu recours à l'immunocytochimie en microscopie électronique, après simple ou double marquage de l'enzyme de synthèse tyrosine hydroxylase (TH) et de VGLUT2, pour déterminer la présence de l'une et/ou l'autre protéine dans les terminaisons (varicosités) axonales de ces neurones et caractériser leur morphologie ultrastructurale dans diverses conditions expérimentales. Dans un premier temps, des rats jeunes (P15) ou adultes (P90), ainsi que des rats des deux âges soumis à l'administration intraventriculaire cérébrale de la cytotoxine 6-hydroxydopamine (6-OHDA) dans les jours suivant la naissance, ont été examinés, afin d'étayer l'hypothèse d'un rôle de VGLUT2 au sein des neurones DA, au cours du développement normal ou pathologique de ces neurones. Chez le jeune rat, ces études ont montré: i) la présence de VGLUT2 dans une fraction importante des varicosités axonales TH immunoréactives du coeur du noyau accumbens ainsi que du néostriatum; ii) une augmentation de la proportion de ces terminaisons doublement marquées dans le noyau accumbens par suite de la lésion 6-OHDA néonatale; iii) le double marquage fréquent des varicosités axonales appartenant à l'innervation DA aberrante (néoinnervation), qui se développe dans la substance noire, par suite de la lésion 6-OHDA néonatale. Des différences significatives ont aussi été notées quant à la dimension des terminaisons axonales marquées pour la TH seulement, VGLUT2 seulement ou TH et VGLUT2. Enfin, à cet âge (P15), toutes les terminaisons doublement marquées sont apparues dotées d'une spécialisation membranaire synaptique, contrairement aux terminaisons marquées pour la TH ou pour VGLUT2 seulement. Dans un deuxième temps, nous avons voulu déterminer le devenir du double phénotype chez le rat adulte (P90) soumis ou non à la lésion 6-OHDA néonatale. Contrairement aux observations recueillies chez le jeune rat, nous avons alors constaté: i) l'absence complète de terminaisons doublement marquées dans le coeur du noyau accumbens et le néostriatum d'animaux intacts, de même que dans les restes de la substance noire des animaux 6-OHDA lésés; ii) une très forte baisse de leurnombre dans le coeur du noyau accumbens des animaux 6-OHDA lésés. Ces observations, suggérant une régression du double phénotype TH/VGLUT2 avec l'âge, sont venues renforcer l'hypothèse d'un rôle particulier d'une co-libération de glutamate par les neurones mésencéphaliques DA au cours du développement. Dans ces conditions, il est apparu des plus intéressants d'examiner l'innervation DA méso-striatale chez deux lignées de souris dont le gène Vglut2 avait été sélectivement invalidé dans les neurones DA du cerveau, ainsi que leurs témoins et des souris sauvages. D'autant que malgré l'utilisation croissante de la souris en neurobiologie, cette innervation DA n'avait jamais fait l'objet d’une caractérisation systématique en microscopie électronique. En raison de possibles différences entre le coeur et la coque du noyau accumbens, l'étude a donc porté sur les deux parties de ce noyau ainsi que le néostriatum et des souris jeunes (P15) et adultes (P70-90) de chaque lignée, préparées pour l'immunocytochimie de la TH, mais aussi pour le double marquage TH et VGLUT2, selon le protocole précédemment utilisé chez le rat. Les résultats ont surpris. Aux deux âges et quel que soit le génotype, les terminaisons axonales TH immunoréactives des trois régions sont apparues comparables quant à leur taille, leur contenu vésiculaire, le pourcentage contenant une mitochondrie et une très faible incidence synaptique (5% des varicosités, en moyenne). Ainsi, chez la souris, la régression du double phénotype pourrait être encore plus précoce que chez le rat, à moins que les deux protéines ne soient très tôt ségréguées dans des varicosités axonales distinctes des mêmes neurones DA. Ces données renforcent aussi l’hypothèse d’une transmission diffuse (volumique) et d’un niveau ambiant de DA comme élément déterminant du fonctionnement du système mésostriatal DA chez la souris comme chez le rat., Knowing that a subset of rat and mouse mesencephalic dopamine (DA) neurons expresses the mRNA of the vesicular glutamate transporter type 2 (VGLUT2), we used electron microscopic immunocytochemistry, after single or double labeling of the biosynthetic enzyme tyrosine hydroxylase (TH) and of VGLUT2, to determine the presence of one and/or both proteins in axon terminals (varicosities) of these neurons and characterize their ultrastructural morphology under various experimental conditions. At first, young (P15) or adult (P90) rats, subjected or not to cerebro-ventricular administration of the cytotoxin 6-hydroxydopamine (6-OHDA) a few days after birth, were examined in order to investigate the role of VGLUT2 in DA neurons during normal and pathological development of these neurons. In the young rats, these studies revealed: i) the presence of VGLUT2 in a significant fraction of TH immunoreactive varicosities in the core of the nucleus accumbens and the neostriatum; ii) an increase in the proportion of dually labeled terminals in the nucleus accumbens following neonatal 6-OHDA lesion; iii) frequent double labeling of TH varicosities belonging to the aberrant DA innervation (neoinnervation) which develops in the substantia nigra following neonatal 6-OHDA lesion. Significant differences were also noted in the size of the axon terminals labeled for TH only, VGLUT2 only, or TH and VGLUT2. Finally, at this age (P15), all the dually labeled terminals appeared equipped with a synaptic membrane specialization, unlike the terminals labeled for TH or for VGLUT2 only. In a second step, we sought to determine the fate of the dual phenotype in adult rats (P90) subjected or not to the neonatal 6-OHDA lesion. In contrast with the observations made in young rats, we found: i) a complete absence of dually labeled terminals in the core of the nucleus accumbens and striatum of intact animals, as well as in the remains of the substantia nigra after neonatal 6-OHDA lesion; ii) a sharp decline of their number in the core of the nucleus accumbens of 6-OHDA-lesioned animals. These findings, suggesting a regression of the dual TH/VGLUT2 phenotype with age, reinforced the hypothesis of a specific role of the co-release of glutamate from midbrain DA neurons during development. Under these conditions, it was of considerable interest to examine the DA meso-striatal innervation in two strains of mice whose Vglut2 gene has been selectively invalidated in DA neurons, as well as in their control littermates and wild-type mice. This issue was particularly relevant with the increasing use of genetically modified mice in neurobiology; indeed, this DA innervation had never been systematically characterized by electron microscopy. Because of possible differences between the core and shell of the nucleus accumbens, the study included both parts of this nucleux as well as the striatum of young (P15) and adult (P70-90) mice of each strain, prepared for TH immunocytochemistry, and also for double labeling of TH and VGLUT2, according to the protocol previously used in rats. The results were surprising. At both ages, regardless of the genotype, the TH immunoreactive axon terminals of the three regions appeared comparable in size, vesicle content, percent with mitochondria, and exceeding low frequency of synaptic membrane specialization (5% of varicosities, on average). Thus, in mice, the regression of the dual phenotype might be even more precocious than in rats, unless the two proteins are segregated very early in different axon terminals of the same DA neurons. These data also strenghten the hypothesis of a diffuse (volume) transmission and of an ambient level of DA as determinant elements in the functioning of the meso-striatal DA system in mice as well as rats.

Changes in the substantia nigra of patients with Parkinson's disease were suspected by Brissaud in the late 19th century. They were subsequently confirmed by Tretiakoff but neglected by Lewy, who described the inclusion bodies that bear his name. The experimental Parkinsonian syndrome caused by reserpine led Carlsson to discover the neuromediatory role of dopamine, a finding at the origin of L-DOPA therapy. Identification of a mutation of the alpha-synuclein gene in cases of familial Parkinson's disease with autosomal dominant transmission was followed by the detection of the protein product in Lewy bodies and neurites. Alpha-synuclein is now recognized as being the main constituent of Lewy bodies. Alpha-synuclein immunohistochemistry has revealed that lesions can extend from the autonomous nervous system to the cortex (in Lewy body dementia). The Lewy body itself does not appear to be the direct cause of symptoms, which correlate better with neuronal death. Neuronal death could be due to metabolic disturbances related to alpha-synuclein accumulation, ubiquitin-proteasome system dysfunction, or oxidative stress. Non-autonomous cell death, caused by neuro-inflammation or gliosis, has also been incriminated.

No validated biomarker is yet available for Parkinson's disease (PD). Clinical PD symptoms include dopa-responsive motor symptoms and dopa-resistant non motor symptoms. Some of the non motor symptoms begin during the premotor stage, like constipation, hyposmia or REM-sleep disorders. Dementia, gait disorders and dysarthria occur in later stages of the disease. PD pathology extends well beyond the substantia nigra. It affects autonomic and non autonomic nuclei in the brainstem and in the medulla, the olfactory bulb and the peripheral autonomic nervous system. Alpha-synuclein aggregates, called Lewy bodies and Lewy neurites, are detectable in these structures at early stages. The study of the enteric nervous system (ENS) displays the Lewy pathology in living patients through the digestive biopsies. Minor salivary glands analysis could be a good marker as well, but this needs confirmation. An anatomopathologic PD biomarker would be interesting at different stages of PD: for the positive diagnosis, to follow the progression and to develop neuroprotective treatments.

This work concerns the functional study of two genes preferentially expressed in two brain regions affected by neurodegenerative diseases: Capucine, a marker of the striatum, a structure that degenerates in Huntington's disease and Agpat4, a marker of the ventral tegmental area and the substantia nigra pars compacta, whose dopaminergic neurons are selectively affected in Parkinson's disease. Mouse lines deficient for Capucine and Agpat4 have been generated in the laboratory and during my PhD thesis I carried out their characterization.As the striatal gene expression of Capucine is significantly reduced in mouse models of Huntington's disease, we wished to evaluate its possible role in the pathogenesis of this disease. In a collaborative work, we examined the effect of the knockout and overexpression of the Capucine gene on the vulnerability of striatal neurons to a mutant Huntingtin fragment in a mouse model of Huntington’s disease. The data show that Capucine has no significant effect on the toxicity of the mutant Huntingtin fragment in the considered model.The Agpat4 protein has sequence homologies with acyltransferases involved in the metabolism of phosphoglycerides. I conducted expression studies using different molecular biology techniques, which showed that the Agpat4 gene is expressed in most catecholaminergic tissues. To determine the endogenous activity of Agpat4 and its physiological role in the tissues where it is expressed, I compared the metabolomes of Agpat4-deficient and wild-type mice tissues by liquid chromatography coupled with mass spectrometry. My results indicate that Agpat4 deficiency alters not only the metabolism of different lipid classes, in particular lysophosphatidylethanolamines, but also the metabolism of catecholamines., Ce travail porte sur l’étude fonctionnelle de deux gènes préférentiellement exprimés dans deux régions du cerveau touchées par des pathologies neurodégénératives : Capucine, un marqueur du striatum, structure qui dégénère au cours de la maladie de Huntington et Agpat4, un marqueur de l’aire tegmentaire ventrale et de la substance noire compacte, dont les neurones dopaminergiques sont sélectivement atteints lors de la maladie de Parkinson. Des lignées de souris invalidées pour ces gènes ont été générées au laboratoire et au cours de ma thèse j’ai procédé à leur caractérisation. L’expression striatale du gène de la Capucine étant significativement diminuée dans des modèles murins de la maladie de Huntington, nous avons souhaité évaluer son rôle éventuel dans la pathogenèse de cette maladie. Pour ce faire, nous avons examiné, dans le cadre d’une collaboration, l’effet du knock-out et de la surexpression du gène de la Capucine sur la vulnérabilité des neurones striataux à un fragment de la Huntingtine mutée dans un modèle murin de la maladie de Huntington. Les données montrent que la Capucine n’a pas d’effet significatif sur la toxicité du fragment de la Huntingtine mutée dans le modèle étudié.La protéine Agpat4 présente des homologies de séquence avec des acyltransférases impliquées dans le métabolisme des phosphoglycérides. J’ai réalisé des études d’expression par différentes techniques de biologie moléculaire qui montrent que le gène d’Agpat4 est exprimé dans la plupart des tissus catécholaminergiques. Pour déterminer l’activité endogène d’Agpat4 et son rôle physiologique dans les tissus où elle est exprimée, j’ai comparé le métabolome de tissus de souris invalidées pour le gène d’Agpat4 et sauvages par chromatographie en phase liquide couplée à la spectrométrie de masse. Mes résultats indiquent que l’invalidation du gène d’Agpat4 perturbe le métabolisme non seulement de différentes classes de lipides, notamment les lysophosphatidyléthanolamines, mais aussi celui des catécholamines.

This work concerns the functional study of two genes preferentially expressed in two brain regions affected by neurodegenerative diseases: Capucine, a marker of the striatum, a structure that degenerates in Huntington's disease and Agpat4, a marker of the ventral tegmental area and the substantia nigra pars compacta, whose dopaminergic neurons are selectively affected in Parkinson's disease. Mouse lines deficient for Capucine and Agpat4 have been generated in the laboratory and during my PhD thesis I carried out their characterization.As the striatal gene expression of Capucine is significantly reduced in mouse models of Huntington's disease, we wished to evaluate its possible role in the pathogenesis of this disease. In a collaborative work, we examined the effect of the knockout and overexpression of the Capucine gene on the vulnerability of striatal neurons to a mutant Huntingtin fragment in a mouse model of Huntington’s disease. The data show that Capucine has no significant effect on the toxicity of the mutant Huntingtin fragment in the considered model.The Agpat4 protein has sequence homologies with acyltransferases involved in the metabolism of phosphoglycerides. I conducted expression studies using different molecular biology techniques, which showed that the Agpat4 gene is expressed in most catecholaminergic tissues. To determine the endogenous activity of Agpat4 and its physiological role in the tissues where it is expressed, I compared the metabolomes of Agpat4-deficient and wild-type mice tissues by liquid chromatography coupled with mass spectrometry. My results indicate that Agpat4 deficiency alters not only the metabolism of different lipid classes, in particular lysophosphatidylethanolamines, but also the metabolism of catecholamines., Ce travail porte sur l’étude fonctionnelle de deux gènes préférentiellement exprimés dans deux régions du cerveau touchées par des pathologies neurodégénératives : Capucine, un marqueur du striatum, structure qui dégénère au cours de la maladie de Huntington et Agpat4, un marqueur de l’aire tegmentaire ventrale et de la substance noire compacte, dont les neurones dopaminergiques sont sélectivement atteints lors de la maladie de Parkinson. Des lignées de souris invalidées pour ces gènes ont été générées au laboratoire et au cours de ma thèse j’ai procédé à leur caractérisation. L’expression striatale du gène de la Capucine étant significativement diminuée dans des modèles murins de la maladie de Huntington, nous avons souhaité évaluer son rôle éventuel dans la pathogenèse de cette maladie. Pour ce faire, nous avons examiné, dans le cadre d’une collaboration, l’effet du knock-out et de la surexpression du gène de la Capucine sur la vulnérabilité des neurones striataux à un fragment de la Huntingtine mutée dans un modèle murin de la maladie de Huntington. Les données montrent que la Capucine n’a pas d’effet significatif sur la toxicité du fragment de la Huntingtine mutée dans le modèle étudié.La protéine Agpat4 présente des homologies de séquence avec des acyltransférases impliquées dans le métabolisme des phosphoglycérides. J’ai réalisé des études d’expression par différentes techniques de biologie moléculaire qui montrent que le gène d’Agpat4 est exprimé dans la plupart des tissus catécholaminergiques. Pour déterminer l’activité endogène d’Agpat4 et son rôle physiologique dans les tissus où elle est exprimée, j’ai comparé le métabolome de tissus de souris invalidées pour le gène d’Agpat4 et sauvages par chromatographie en phase liquide couplée à la spectrométrie de masse. Mes résultats indiquent que l’invalidation du gène d’Agpat4 perturbe le métabolisme non seulement de différentes classes de lipides, notamment les lysophosphatidyléthanolamines, mais aussi celui des catécholamines.

Despite the fact that the neurotransmitter dopamine was discovered more than 50 years ago, we still have limited knowledge of its physiological and pathological roles. Recent work has unveiled novel and surprising properties of dopamine neurons and of other key players involved in regulating the dopamine system. For example, the integration of the dopamine signal by its receptors depends on many proteins of diverse signaling pathways and also of other types of receptors that interact with and regulate dopamine receptors: many new promising interactions have been reported during the past few years. Also, we are beginning to discover that chronic treatment with dopamine receptor ligands or other molecules affecting dopaminergic pathways induce long-term molecular, structural and functional rearrangements that could ultimately force us to revisit the mechanism of action of established therapeutic agents. Finally, the discovery of glutamate co-release by dopamine neurons is leading us to reconsider some keys aspects of dopamine neuron physiology.

In contrast to monoaminergic (MA-ergic) neurons possessing the whole set of the enzymes for MA synthesis from the precursor amino-acid, some, mostly peptidergic, neurons co-express only one of the enzymes of monoamine synthesis. They are widely distributed in the brain, being particularly numerous in ontogenesis and, in adulthood, under certain physiological conditions. Most monoenzymatic neurons possess one of the enzymes for dopamine (DA) synthesis, tyrosine hydroxylase (TH) or aromatic L-amino acid decarboxylase (AADC). TH and AADC are enzymatically active in a substantial number of monoenzymatic neurons, where they are capable of converting L-tyrosine to L-3,4-dihydroxy-phenylalanine (L-DOPA) and L-DOPA to dopamine (DA) (or 5-hydroxy-tryptophan, 5-HTP to serotonin), respectively. According to our data L-DOPA synthesized in monoenzymatic TH-neurons is released and taken up by monoenzymatic AADC-neurons for DA synthesis. Moreover, L-DOPA captured by dopaminergic neurons and serotoninergic neurons serves to stimulate dopamine synthesis in the former and to start DA synthesis in the latter. Cooperative synthesis of MAs is considered as a compensatory reaction under a failure of MA-ergic neurons, e.g. in neurodegenerative diseases like hyperprolactinemia and Parkinson's disease, which are developed primarily because of degeneration of DA-ergic neurons of the tuberoinfundibular system and the nigrostriatal system, respectively. Noteworthy, the neurotoxin-induced increase of prolactin secretion returns with time to a normal level due to the stimulation of DA synthesis by the tuberoinfundibular most probably monoenzymatic neurons. The same compensatory mechanism is supposed to be used under the failure of the nigrostriatal DA-ergic system that is manifested by an increased number of monoenzymatic neurons in the striatum of animals with neurotoxin-induced parkinsonism and in humans with Parkinson's disease. Expression of the enzymes of MA synthesis in non-monoaminergic neurons is controlled by intercellular signals such as classical neurotransmitters (catecholamines), etc. Thus, a substantial number of brain neurons express partly the monoaminergic phenotype, namely individual complementary enzymes of MA synthesis, serving to produce MAs in cooperation, which is considered as a compensatory reaction under the failure of MA-ergic neurons.

Progressive supranuclear palsy (PSP) is classically characterized by supranuclear ophthalmoplegia, paroxysmal imbalance with backward falling, axial dystonia, rigidity, pseudobulbar palsy and cognitive dysfunction. However, incomplete or atypical clinical presentation has been previously reported, but in all these cases, the patients had at least one of the main clinical features of the disease (ophthalmoplegia, parkinsonian syndrome or cognitive dysfunction).A 60-year-old woman presented with nocturnal agitation and choreiform movements. A few months later she developed severe swallowing disorders, caused by achalasia of the upper esophageal sphincter, and responsible for recurrent acute respiratory distress and pneumonia, prevailing to tracheotomy and gastrostomy. She died suddenly two years after the onset of the symptoms.Postmortem examination of brain revealed a tauopathy, with deposition of abnormal phosphorylated tau in threads and in coiled-shaped as well as globose tangles in the brainstem, subthalamic nuclei and hippocampus. Nuclei of the medulla, including the vagus/solitarius complex and the region of the nucleus ambiguous were especially rich in tau positive inclusions. Ultrastructural analysis of globoid-shaped tangles in the brainstem revealed the presence of straight and paired helicoidal filaments compatible with a PSP.This case contributes to improve knowledge of the clinical phenotypic range of PSP. In this case, the neuropathological lesions accounted for most of the symptoms. However, the early death of the patient was probably related to the particular distribution of the neuropathological lesions. This case suggests that the initial neuropathological changes in PSP is located in the dorsal brainstem.

The subthalamic nucleus (STN) is the main target of deep brain stimulation (DBS) treatment for severe idiopathic Parkinson's disease. But there is still no clear information on the location of the effective contacts (used during the chronic phase of stimulation). Our aim was to assess the anatomical structures of the subthalamic area (STA) involved during chronic DBS. Ten patients successfully treated were included. The surgical procedure was based on direct STN targeting (stereotactic MRI based) pondered by the acute effects of intraoperative stimulation. We used a formaldehyde-fixed human specimen to compare by matching MRI images obtained at 1.5 Tesla (performed in clinical stereotactic conditions) and at very high field at 4.7 Tesla. This allowed accurate analysis of the anatomy of the STA and retrospective precision of the location of the center of effective contacts which were located within the STN in 4 patients, at the interface between the STN and the ZI and/or FF in 13, at the interface between ZI and FF in 2 and between the STN and the substantia nigra in one. These results were consistent with the literature, revealing the implication of neighboring structures, especially the zona incerta and Forel's Field, in the clinical benefit.

Efficacy of high frequency subthalamic nucleus (STN) stimulation has been demonstrated in idiopathic Parkinson's disease (IPD). However, since it may be difficult to differentiate IPD from multiple system atrophy with parkinsonian presentation (MSA-P), a few cases of MSA-P has been treated by deep brain stimulation (DBS) and showed no sustained improvement of clinical signs. We report a patient with a clinical misdiagnosed MSA-P, later confirmed by neuropathological study, who was improved by DBS for one year.A 63-year-old parkinsonian patient had been treated by levodopa for 6 years with a persistent good response. Over one year he progressively developed disabling fluctuations with severe axial syndrome and vegetative non motor symptoms in off periods. After checking usual contraindications, he was included in surgical procedure protocol (bilateral STN stimulation). During the first year after surgery, the clinical status improved with disappearance of non motor fluctuations, a 45 percent decrease of the OFF UPDRS III score, and a 39 percent reduction of the treatment. However after one year, axial symptoms reappeared with recurrent falls, as well as increasing dysarthry and swallowing difficulties which were only slightly improved by levodopa. He developed severe urinary disorders increased by a prostatic adenoma which led to surgical treatment. During the post operative period, 2 years after DBS, he died suddenly from an unexplained cause. A cerebral autopsy was performed and showed a good position of the two electrodes in the STN. Microscopic studies revealed severe neuronal depletion in the substantia nigra but no Lewy bodies. Immunohistochemical methods demonstrated numerous argyrophilic glial cytoplasmic inclusions positive for alpha-synuclein and ubiquitin in the STN, putamen, globus pallidus, pontine nuclei and cerebellar white matter, significant of MSA.This case shows that DBS can improve parkinsonian signs in MSA-P with persistent dopa sensitivity. However, probably because of striatal degeneration progression, this improvement is time limited and STN DBS cannot be recommended in MSA.

Parkinson's disease is characterized by the progressive and selective loss of the dopaminergic neurons in the substantia nigra and the presence of ubiquitinated protein inclusions termed Lewy bodies. In the past six years, four genes involved in rare inherited forms of Parkinson's disease have been identified: mutations in the alpha-synuclein and ubiquitin carboxyterminal hydrolase L1 genes (UCH-L1) cause autosomal dominant forms, whereas mutations in the Parkin and DJ-1 genes are responsible for autosomal recessive forms of the disease. A toxic gain of function related to the ability of alpha-synuclein to assemble into insoluble amyloid fibrils may underlie neuronal cell death in parkinsonism due to alpha-synuclein gene mutations. In contrast, loss of protein function appears to be the cause of the disease in parkinsonism due to mutations in the genes encoding Parkin and UCH-L1, which are key enzymes of the ubiquitin-proteasome pathway. The presence of alpha-synuclein, Parkin and UCH-L1 in Lewy bodies suggests that dysfunction of pathways involved in protein folding and degradation is not only involved in the pathogenesis of familial Parkinson's disease, but could also play a role in the frequent sporadic form of the disease (idiopathic Parkinson's disease).

MR imaging of the brain, particularly with high field MR imagers, may demonstrate signal abnormalities consistent with deposits of iron or other paramagnetic substances in extrapyramidal disorders. The diagnosis of Parkinson's disease and progressive supranuclear palsy can be made on clinical grounds in most of the cases and MR signs are of little help in the diagnosis of these diseases. In patients with parkinsonian disorders poorly responding to therapy, MR imaging may be useful in demonstrating signal abnormalities in the putamen that may help to establish the diagnosis of striatonigral degeneration (component of multiple system atrophy) with a poorer prognosis than Parkinson's disease. Finally, MR imaging may be useful in the exclusion of other disease processes.

The MRI exploration of a woman suspected, on clinical grounds, of having Hallervorden-Spatz disease (or rather syndrome) revealed, on T2-weighted sequences, the "tiger's eye" or "target" image of the pallidum described by previous authors: i.e. a high-intensity signal in the centre of a distinct low-intensity signal; it also showed an abnormal low-intensity signal of the substantia nigra. These changes are related to the iron deposits and neuro-axonal lesions which characterize the disease. The MRI semeiology of Hallervorden-Spatz disease has been analyzed in the literature. The images we obtained in this patient with the echo-gradient technique using T1-weighted sequences were unusual, showing a low-intensity signal of the globi pallidi surrounded by central and peripheral low-intensity signal areas, whereas the images obtained with spin-echo T1-weighted sequences were normal.

Three types of tachykinin receptors (NK1, NK2 and NK3) have been identified, their endogenous ligands being substance P, neurokinin A and neurokinin B respectively. Peptide agonists and non peptide antagonists are now available allowing to study the functional properties of these receptors which are coupled to G proteins. Depending on the tissue, stimulations of phospholipase C occur with NK1, NK2 or NK3 agonists. Peptide, a C-terminal substance P analog and substance P(1-7) seem to act on tachykinin receptors distinct from those of the NK1, NK2 or NK3 type. NK2 binding sites have not been visualized in the brain. Nevertheless, biological responses of the NK2 type have been shown both in the substantia nigra and the striatum in studies on dopamine release.

Within the past decade, the harmonious anatomic aspect of the basal ganglia has changed for inhomogeneous structures filled up with a wealth of neurotransmitters and receptor subtypes with massive vertical and horizontal interconnections, asking for new mathematical concepts like parallel distributed processing of computation to approach their respective functions. Moreover, not only the motor control, but also some important aspects of cognition, eye motions, and limbic functions seem to be processed in the basal ganglia. Their overall threshold of activity seems to be under the bipolar control of the substantia nigra and the subthalamic nucleus; this results in hyper or hypokinetic syndromes. Few practical or therapeutical results have come out from the last radiological technologies and biochemical studies of extrapyramidal disorders, but the wealth of information brings hope for new issues from the knowledge in molecular biology, neuropharmacology, and from earlier diagnosis of these diseases in the future.

Five cases of parkinsonism with athymhormia observed in a single family are reported. Death caused by central respiratory disorders occurred after 6 to 8 years of progressive course. In 2 cases with autopsy, there was a severe neuronal loss predominant in the substantia nigra. Other brain stem nuclei (locus coeruleus, dorsal motor nucleus of the vagus nerve, nucleus of the tractus solitarius) were involved, as well as the striatum, pallidum and frontal cortex. No Lewy body was seen. In the surviving patient, positron emission tomography demonstrated, 4 years after the onset, a bilateral frontal hypometabolism. This disease is a rare variety of familial parkinsonism of dominant inheritance, already reported in 2 Canadian families by Perry et al. (1975) and Purdy et al. (1978) and in a family of West Virginia by Roy et al. (1988). The respiratory disorders can be explained by the involvement of the dorsal medullary nuclei. The peculiar neuropsychological disorder and motor slowing are best accounted for by the functional impairment of both motor and limbic striato-pallido-thalamo-frontal loops.

Children with metabolic or toxic diseases affecting the brain stem were examined by MRI in an attempt to obtain images of brain stem systematization fibres and to determine their origin. A toxic cause may be envisaged in hazy, ill-systematized lesions, and a metabolic cause in well-systematized lesions.

Using a double-labelling procedure, morphological relationships existing between dopaminergic and indoleaminergic neuronal systems in rat brain were investigated. Firstly, thanks to a tryptamine (T) antiserum, we visualized this indoleamine in all mesencephalic regions and showed that the T-immunoreactivity (IR) seems to overlap with the staining observed from serotonin (HT) and 5-methoxytryptamine (MT) antisera. Secondly, using a monoclonal anti-dopamine (DA) antibody and our anti-T antibodies, the simultaneous and specific detection of these compounds enabled us to define the chemically relationships existing between the dopaminergic and tryptaminergic neuronal systems from substantia nigra to raphe nuclei. No co-localization exists. But, the intensity of T-IR decreases from the back to the front, whereas the DA-staining decreases in the opposite way, indicating possible interactions at the end of substantia nigra and B9 area.

Severe akinesia can be observed in macaques following MPTP injections destroying dopaminergic nigrostriatal neurons. Akinesia also results from inhalation of toxic substances inducing bilateral lesions of the two pallidal nuclei and of the pars reticulata of the substantia nigra, and not of the pars compacta. Most of the recent studies of the anatomo-physiological substratum of akinesia used MPTP injections. Deoxyglucose studies have shown a clear increase in the neuronal activity of the medial nucleus of the pallidum and of its thalamic projection territory. Electrophysiological studies have shown a major modification of the spontaneous activity of medial pallidal neurons which is influenced in an excessive and non selective manner by sensorimotor inputs. Analysis of the relative three dimensional geometry of nervous arborizations have shown that the striato-pallido-nigral system is extremely convergent. Akinesia consecutive to nigrostriate lesions could be linked to an excessive and anarchic activation of this system. The contradiction which exists between akinesia with an abnormal activity of the medial pallidum and akinesia with bilateral pallidal lesions could only be apparent if akinesia was linked to the ineffective emission or to the interruption of messages to the thalamus.

Huntington's chorea is a degenerative disorder of the human brain characterized by a marked loss of intrinsic neostriatal neurons. This situation can be reproduced by kainic acid injection in the caudate nucleus. Activity of pars reticulata neurons ipsilateral to the injected neostriatum was studied in normal, control (saline-injected) and lesioned rats. They were identified by electrophysiological and histological criteria (Fig. 1). Results obtained in normal and control rats were very similar (Table I). As previously described, the mean frequency of these neurons was high. An important percentage (respectively 72.5 and 73%) and these neurons presented the characteristics of a regular firing pattern (so called "organized neurons"). Results obtained in kainic acid lesioned rats were significantly different (Table I). The mean frequency was lower and only 11% of reticulata cells remained organized after neostriatal lesion. This important dysfunction may be explained in various ways: The neostriato-nigral pathway's destruction involves both the inhibitory GABAergic tract and the excitatory substance P tract (GALE et al., 1978). Other inputs arising from many structures in the brain continue to exert their own action on SN neurons, resulting in an unbalance in the SN inputs. It is well known that the nigral dopamine influences the neuronal activity of pars reticulata neurons (Ruffieux et Schultz, 1980; Waszczak et Walters, 1983). Doudet et al. (1984 b) previously reported a dysfunction of neuronal activity of dopaminergic cells after striatal lesion. A disturbance in the electrical activity may induce a similar disturbance in the intranigral dendritic release of DA.(ABSTRACT TRUNCATED AT 250 WORDS)

Sleep and memory were investigated in a well educated patient suffering from striato-nigral degeneration. Despite almost total insomnia (only 591 min of stages 1 and 2, without any stage 3, 4 or paradoxical sleep during a continuous 4 day recording) it was not possible to objectify significant short or long term memory impairment.

The lesions of Parkinson's disease chiefly involve the dopaminergic nigrostriatal tract and the great subcortical-cortical dopaminergic, noradrenergic, serotoninergic and cholinergic neuron systems. On the basis of these data, one may suggest a mechanism for some motor and mental disorders, as well as the rationale for treatment with L-dopa, the origin of its main side-effects and the classical escape phenomenon observed with this drug.

The use of Leão's spreading depression for studying the action of connections between central structures is examined. Extracellular recordings of cortical and striatal spreading depressions with single microelectrodes are presented using both a DC channel and spike recordings systems. Striatal spreading depression was produced by peristaltic perfusion of a KC1 solution via a push-pull cannula system. The characteristics of cortical and striatal spreading depressions were studied and their effects on antidromically provoked cellular spikes. Using double microelectrode recordings modifications of spontaneous activity provoked by cortical spreading depression were examined in n. ventralis posterior (VP) and centralis lateralis (CL) of the thalamus. In both nuclei a silence corresponding to the block of spontaneous activity of a localised cortical area was observed. The controls originated from different cortical regions for each nucleus. The discharge preceeding the onset of the spreading depression slow wave is reflected by a similar discharge in VP but not in CL. The differences in the frequency following of CL and VP was examined in order to explain this discrepancy. The results just summarized can be explained if we accept that a tonic facilitatory control exists between localised cortical areas and the two thalamic nuclei studied. Similar experiments were performed to study the controls exerted by cortical areas on dorsal column nuclei. Only phasic transitory effects were observed which were either an increase or a decrease in activity. These facilitatory or depressive effects were attributed to the initial excitation signalling the propagation of a cortical spreading depression. No tonic effects were observed. Striatal spreading depression was not accompanied by a cortical effect but on the contrary the activity of cells in substantia nigra was significantly altered. In pars reticulata two populations could be distinguished. The first presented a phasic increase followed by a long period of decreased activity, they are proposed to be under the control of striatum via an excitatory pathway. The second was initially depressed then presented a long period of increased activity. This probably reflects the block of an inhibitory striato-nigral pathway. Both striato nigral effects were tonic in nature. The possibility of separating the effects due to cortical excitation or cortical block are discussed as well as the problems of interpretation of long distance changes in cellular activity.

Substance P (SP) is a polypeptide formed by 11 amino acids of the tachykinin family. SP is found in the peripheral nervous system, particularly in small diameter myelinated and non myelinated afferent fibers. It is concentrated at both proximal and distal ends of sensory neurones to the skin, mucous membranes, viscera and vessels throughout the body. In the central nervous system SP is concentrated in the basal ganglia (striatonigral system), the habenulo-interpeduncular system, the brain stem (particularly in afferent spinal tract neurones) and the hypothalamus. Neurones containing SP may also contain other neurotransmitters. Criteria for identification of SP are similar to those applying to other neuromediators except for duration of action, which is comparatively greatly prolonged for SP. SP exerts complex synaptic effects, both pre- and post-synaptic, and usually acts as an activating factor. Its physiological role is unknown but it could intervene in peripheral nociceptive processes by its peripheral (oedema and plasma extravasation) and central (excitation of dorsal horn sensory neurones and facilitation of medullary reflexes by depolarization of motor neurones) effects; in central regulation of nociceptive impulses (analgesic effect); in regulation of some vegetative functions (glandular secretion, digestive and vasomotor motility, hypothalamic functions); in certain motor regulatory actions as suggested by the large amounts of SP in the striatonigral tract and the motor effects induced by injection of SP into the substantia nigra; in control of some learning processes; in control of growth of some central nerve fibers during development.

Local cerebral glucose utilization (LCGU) was studied quantitatively in awake rats one week and one month following unilateral electrolytic lesion of the ventromedial thalamic nucleus (VM). Significant decrease in LCGU were observed in the ipsilateral cortex as well as in some contralateral cortical areas and bilateral subcortical structures. The modifications by the VM lesion, of the metabolic activations induced by electrical stimulation of substantia nigra pars reticulata (SNR, main afference of the VM) were investigated also. Results suggest that VM is an important relay nucleus on the pathways directed from one SNR towards ipsilateral corticostriatal system and contralateral thalamus and basal ganglia. Finally, one month following the VM lesion a recovery of metabolic activations induced by SNR stimulation was observed whereas basal glucose consumption remained decreased.

Six clinico-pathological cases (4 males and 2 females) with a Parkinson-like syndrome which lasted an average of 5 1/2 years are reported. The average age at death was 73 years. Neuropathological features were similar to those described in post encephalitic Parkinson's syndrome and in Steele-Richardson-Olszewski disease. However, neurofibrillary tangles were less numerous; lesions in tectal, periaqueductal and reticular structures were less severe. Furthermore, the lesions seemed more pronounced in the substantia nigra, the globus pallidus and the nucleus subthalamicus, giving the appearance of a systematic pallido-luyso-nigral atrophy. None of these patients had a history of encephalitis. Clinical examination did not reveal the dystonic rigidity in extension of the neck nor the characteristic ophthalmoplegia of progressive supranuclear palsy. These 6 cases are compared to 10 cases of progressive supranuclear palsy typical both on clinical and pathological grounds. They could be considered as a particular form of Steele-Richardson-Olszewski disease without ophthalmoplegia.

The demonstration of fluorescent catecholamines and horseradish peroxidase (HRP) in the same neuron has been achieved in the Rat in two ways: by submitting vibratome sections to a modified glyoxylic acid fluorescence method followed by the usual procedure to reveal HRP; or by combining the last procedure with the cryostat technique of Chiba et coll. After HRP injection into the striatum or the nucleus accumbens of the Rat, non-fluorescent HRP labelled neurons were observed in the substantia nigra and the ventral tegmental area respectively, in addition to the HRP labelled fluorescent dopaminergic neurons.

Using a retrograde tracer technique with horseradish peroxidase, we have revealed some afferent projections to the locus coeruleus complex from the contralateral pontine tegmentum, raphe nuclei, substantia nigra, nucleus of the solitory tract, dorsal motor nucleus of the vagus and other regions of the ponto-bulbar reticular formation as well as from hypothalamic and preoptic areas.

The authors report two anatomo-clinical cases of striato-nigral degeneration with trial of L-Dopa; one of them included an olivoponto-cerebellar degeneration. The features of this degeneration are compared with the literature and related to heredo-degenerative diseases of the nervous system.

The hypothesis linking decreased serotonin transmission to reduced anxiety as the mechanism in the anxiolytic activity of benzodiazepines conflicts with most clinical observations. Serotonin antagonists show no marked capacity to alleviate anxiety. On the other hand, clinical signs of reduced serotonergic transmission (low 5-HIAA levels in the cerebrospinal fluid) are frequently associated with aggressiveness, suicide attempts and increased anxiety. This brief review attempts to reconcile these human and animal findings by investigating whether anxiety reduction or increased impulsivity are likely to account for animal behavioral changes associated with decreased serotonergic transmission. The effects of manipulating central serotonin on experimental anxiety paradigms in animals (punishment, novelty) are reviewed and compared to the effects of anti-anxiety drugs. Anxiety seems neither necessary nor sufficient to induce control by serotonergic neurons on behavior. Further evidence suggests that behavioral effects of anxiolytics thought to be mediated by decreases in anxiety are not caused by the ability of these drugs to reduce serotonin transmission. Blockade of serotonin transmission, especially at the level of the substantia nigra, results in a shift of behavior towards facilitation of responding. This behavioral shift is particularly marked when there is competition between acting and restraining response tendencies and when obstacles prevent the immediate attainment of an anticipated reward. It is proposed that serotonergic neurons are not only involved in behavioral arousal but also in enabling the organism to arrange or tolerate delay before acting. Decreases in serotonin transmission seem to be associated with the increased performance of behaviors which are usually suppressed though not necessarily because of the alleviation of anxiety which might contribute to the suppression.

The effects of bilateral microinjection of gamma-vinyl GABA (GVG, an irreversible inhibitor of GABA-T) were tested during the development of seizures induced by i.p. administration of 10 mg/kg of kainic acid. Intrahippocampal injection of GVG prevents the development of the seizures at an early stage in about half of the cases. In the remaining animals status epilepticus comparable to that of controls develops. Intra-amygdaloid injection reduces the severity of the seizures from the first motor limbic signs. Finally, intranigral injection prevents the appearance of convulsive status epilepticus or, when it develops, reduces its duration. The role that these three structures could play in the electro-clinical development of kainic acid-induced seizures is discussed.

Results of a clinicopathologic study in 3 cases of nigrostriatal degeneration associated with olivopontocerebellar atrophy are reported. The clinical picture was primarily that of parkinsonism but associated disorders were atypical: sphincter and deglutition disorders, pyramidal signs and action myoclonia; paralysis of vertical gaze (with a deficit of convergence in 1 case) and a cerebellar syndrome in 2 cases; postural hypotension with an invariable pulse, amyotrophy of the hands and a paradoxical response to Dopa: worsening of akineto-hypertonic symptomatology and deglutition disorders in 1 case. Pathologic examination showed similar lesions in the 3 cases: atrophy with pigmentation of the putamen and changes in the substantia nigra, associated with evidence of olivopontocerebellar degeneration. There was marked loss of neurones in the intermediolateral tract in the cord of the patient with the Shy and Drager's syndrome. All cases reported of this abiotrophic association have been of a sporadic nature. The predominance of females, the age of onset and duration of the disease are features that do not differ much from those of pure nigrostriatal degenerative disorders. These cases cannot therefore be considered as a pathological entity but as a particular form of degeneration affecting multiple systems.

Bilateral micro-injections of 6-hydroxydopamine into the substantia nigra or the striatum of the Rat impair the acquisition of a two-way avoidance response. This effect is not due to nutritional deficiencies and it is not associated with changes in locomotor activity.

Anatomo-clinical findings are reported in a case of central nervous system degeneration which began at age 47 and progressed over a three year period. Information obtained prior to the patient's death suggested probable spinocerebellar degeneration with amyotrophies. Postmortem anatomical examination confirmed this diagnosis but also revealed the existence of unsuspected lesions. These clinically non-manifested lesions involved severe pallido-luysian degeneration as well as numerous and diffuse senile plaques. The nosological implications of this case are discussed.

The retrograde axonal transport of an iron-dextran complex was observed in neurons of the substantia nigra and of the intralaminar nuclei of the thalamus, after previous injection into the striatum. The histochemical demonstration of iron is simple and rapid, and can be combined with that of horseradish peroxidase, under precise conditions in the sequence of reactions. The iron-dextran complex revealed to be a valuable material for neuronal connectivity studies in the central nervous system.