<p>We investigated 1) how objects come to serve as landmarks in spatial memory and more specifically how they form part of an allocentric cognitive map and 2) how humans encode multiple connected spatial environments. In both sets of experiments, participants performing a virtual driving task incidentally learned the layout of a town and locations of objects or stores in that town. Their spatial memory and recognition memory for the objects or stores were subsequently tested. To assess whether the objects were encoded allocentrically, we developed a new measurement, pointing consistency. We found that when participants had more limited experience of the environment spatial memory for objects at navigationally relevant locations was more consistent across tested viewpoints than for objects at navigationally less relevant locations. When participants’ attention was focused on the appearance of objects, the navigational relevance effect was eliminated, whereas when their attention was focused on the objects’ locations, this effect was enhanced, supporting the hypothesis that when objects are processed in the service of navigation, rather than merely being viewed as objects, they engage qualitatively distinct attentional systems and are incorporated into an allocentric spatial representation. The results were consistent with evidence from the neuroimaging literature that when objects are relevant to navigation, they not only engage the ventral “object processing stream”, but also the dorsal stream and medial temporal lobe memory system classically associated with allocentric spatial memory. Moreover, in the connected environments, our data were more consistent with the formation of local maps, regardless of whether the neighborhoods were learned together or separately. Only when all visible distinctions between neighborhoods were removed did people behave as if they formed one integrated map. These data are broadly consistent with evidence from rodent hippocampal place cell recordings in connected boxes, and with hierarchical models of spatial coding.</p> / Doctor of Philosophy (PhD)

La course d’endurance active le système de récompense (SR) et est reliée aux comportements de recherche alimentaire. L’influence de la leptine sur l’activité physique (AP) volontaire est bien documentée d’un point de vue physiologique, mais très peu en termes d’impact hédonique. La leptine inhibe l’effet récompensant lié à la consommation de nourriture et joue un rôle semblable pour d’autres types de stimuli. La leptine s’arrime à la forme longue du récepteur à la leptine (Leprb) situé sur les neurones à dopamine (DA) et GABA de l’aire tegmentale ventrale (ATV) dans le mésencéphale. Signal transducer and Activator of Transcription 3 (STAT3) est un facteur de transcription important de la cascade de signalisation de la leptine. La phosphorylation de STAT3 n’est détectée que dans une parcelle des neurones DA positifs pour le Leprb, conférant aux neurones DA STAT3-spécifiques des caractéristiques uniques. Nous avons généré un modèle murin invalidé pour STAT3 sélectivement dans les neurones DA (STAT3DAT-KO). La première expérience consistait à évaluer les paramètres métaboliques de base de notre modèle en utilisant les chambres métaboliques Comprehensive Lab Animal Monitoring System (CLAMS), incluant l’activité ambulatoire, le ratio d’échanges respiratoires (RER) et la production de chaleur. Les STAT3DAT-KO sont hyperactives, démontré par une activité locomotrice augmentée, mais aucune variation entre les deux groupes n’est observée pour le RER et la production de chaleur, en plus d’un gain de poids identique. Une stratégie de récupération ciblant la réinsertion de STAT3 dans les neurones DA du système mésolimbique normalise l’AP anciennement plus élevée des STAT3DAT-KO à celle des contrôles, suivant l’accès libre à une roue d’exercice (RE) pour une durée de 4 semaines, suivant l’accès libre à une roue d’exercice (RE) pour une durée de 4 semaines. L’injection d’un psychostimulant (agoniste du récepteur DA de type 1 (D1R), le Chloro-APB-Hydrobromide (SKF 82958)) reflète une fonction dopaminergique réduite chez les STAT3DAT-KO. Un test de recherche compulsive de nourriture révèle une suppression de la prise alimentaire chez les deux groupes expérimentaux. Nous démontrons pour la première fois que la motivation alliée à la course d’endurance, indépendamment de la régulation de la prise alimentaire par la leptine, est dépendant d’une signalisation leptine-STAT3 amoindrie dans les neurones DA du système mésolimbique, révélant STAT3 comme élément clé dans la régulation du tonus dopaminergique et des propriétés récompensantes de l’AP. / Endurance running is rewarding and related to food seeking behaviors. Influence of leptin on voluntary physical activity is well documented from a physiological point of view, but little is known about its hedonic impact. Leptin inhibits the rewarding aspects of food consumption and plays a similar role for other types of stimuli. Leptin binds to the long form of the leptin receptor, situated on dopamine (DA) and GABA neurons of the ventral tegmental area (VTA) in the midbrain. Signal Transducer and Activator of Transcription 3 (STAT3) is an important transcription factor of the leptin signalling cascade. Phosphorylation of STAT3 is detected only in a subset of neurons that are positive for the leptin receptor, conferring unique properties to DA STAT3 neurons. We generated a mouse model invalidated for STAT3 selectively in dopamine neurons (STAT3DAT-KO). We first assessed basic metabolic parameters of our model using CLAMS metabolic chambers, including ambulatory acitivity, respiratory exchange ratio (RER) and heat production. STAT3DAT-KO are hyperactive as seen by a higher locomotor activity, but there is no inter-group variation of RER and heat production, and the weight gain is the same. A rescue strategy targeting the reinsertion of STAT3 in DA neurons of the mesolimbic system normalizes physical activity of the STAT3DAT-KO - which was previously much higher - to that of the control mice, following free access to a running wheel for a period of 4 weeks. The injection of a psychostimulant (agonist of the type1 DA receptor (D1R), Chloro-APB-Hydrobromide (SKF 82958)) reflects a reduced DA signalling STAT3DAT-KO. A compulsive food seeking test reveals a suppression of sucrose intake in both experimental groups. We demonstrate for the first time that the motivation allied to endurance running, independently of food intake regulation by leptin, is dependent upon a diminished leptin-STAT3 signalling in DA neurons of the midbrain, revealing STAT3 as a key player in the regulation of DA tone and the rewarding properties of physical activity.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / IntroduÃÃo: A ventilaÃÃo nÃo invasiva com pressÃo positiva (VNI) vem tendo uma crescente utilidade na prÃtica clÃnica e o seu uso està bem estabelecido em casos de edema agudo de pulmÃo e nas exacerbaÃÃes da doenÃa pulmonar obstrutiva crÃnica (DPOC), diminuindo a necessidade de intubaÃÃo orotraqueal e melhorando a sobrevida. AlÃm disso, a pressÃo positiva contÃnua em vias aÃreas (CPAP) â modo de VNI â constitui o tratamento de escolha para pacientes portadores da sÃndrome de apnÃia obstrutiva do sono (SAOS), onde geralmente nÃo hà alteraÃÃo no parÃnquima pulmonar. Ainda a aplicaÃÃo de nÃveis elevados de pressÃo positiva expiratÃria final (PEEP) no manejo da sÃndrome do desconforto respiratÃrio agudo (SDRA) està associada tanto ao recrutamento alveolar como à hiperdistensÃo de Ãreas previamente normoaeradas, com resultados ainda indefinidos quanto ao impacto na sobrevida. Um dos recursos para melhora da oxigenaÃÃo nestes pacientes à a posiÃÃo prona e os efeitos da associaÃÃo desta manobra com pressÃo positiva permanecem controversos. A tomografia computadorizada de alta resoluÃÃo (TCAR) constitui um excelente mÃtodo de imagem para avaliaÃÃo qualitativa e quantitativa do parÃnquima pulmonar. O emprego da TCAR pode auxiliar na investigaÃÃo dos efeitos da CPAP de modo nÃo invasivo sobre o parÃnquima pulmonar, contribuindo para a elucidaÃÃo dos efeitos fisiolÃgicos da pressÃo positiva e da posiÃÃo prona. Objetivos: Avaliar e comparar os efeitos de diferentes nÃveis de CPAP de modo nÃo invasivo sobre o parÃnquima pulmonar em indivÃduos sadios nas posiÃÃes supina e prona. CasuÃstica e mÃtodos: Estudo intervencionista com oito voluntÃrios sadios, sem doenÃa cardiopulmonar. Foram realizados cortes tomogrÃficos de alta resoluÃÃo em trÃs regiÃes: Ãpice (2 cm acima do arco aÃrtico), hilo (1 cm abaixo da carina) e base (2 cm acima do diafragma) na posiÃÃo supina, sem CPAP (basal) e com CPAP de 5, 10 e 15 cmH2O; e na posiÃÃo prona, corte em base, sem CPAP e com CPAP de 10 cmH2O. A seqÃÃncia das posiÃÃes e da ordem das pressÃes aplicadas foi randomizada. Aguardava-se um perÃodo de no mÃnimo 5 minutos apÃs completa adaptaÃÃo da mÃscara para realizaÃÃo do exame e o mesmo perÃodo de tempo entre um nÃvel de pressÃo e outro. Os dados foram analisados agrupando-se os cortes tomogrÃficos das trÃs regiÃes e por subdivisÃes em regiÃes ventral, medial e dorsal, sendo calculadas as mÃdias das densidades pulmonares e o percentual do nÃmero de unidades com densidade menor que -950 UH (hiperaeradas) para cada uma das regiÃes. Resultados: NÃo houve diferenÃa das mÃdias das densidades pulmonares entre Ãpice, hilo e base para o mesmo nÃvel de pressÃo. Na posiÃÃo supina, houve reduÃÃo da densidade pulmonar e aumento do percentual de pixels nas Ãreas hiperaeradas com nÃveis crescentes de pressÃo: basal -761 UH e 7,25%; CPAP 5: -780 UH e 8,57%; CPAP 10: -810 UH e 11,62%; CPAP 15: -828 UH e 14,65% (p < 0,05). O mesmo foi observado na posiÃÃo prona: basal -759 UH e 6,30%; CPAP 10: -803 UH e 9,94% (p < 0,05). Este aumento da aeraÃÃo tambÃm foi observado nas regiÃes ventral, medial e dorsal. Foi encontrado um gradiente crescente no sentido ventro-dorsal de densidades pulmonares na posiÃÃo supina e o inverso na posiÃÃo prona. A CPAP de 10 cmH2O, na posiÃÃo prona, ocasionou menor aumento do percentual de pixels nas Ãreas hiperaeradas em relaÃÃo à supina. Nas regiÃes nÃo dependentes do pulmÃo (ventral em supina e dorsal em prona), observou-se um menor percentual de pixels nas Ãreas hiperaeradas e aumento nas normoaeradas na posiÃÃo prona em relaÃÃo à supina, praticamente sem diferenÃa nas regiÃes dependentes. ConclusÃes: A aplicaÃÃo de diferentes nÃveis de CPAP, de modo nÃo invasivo, em voluntÃrios sadios, resultou em maior aeraÃÃo com nÃveis crescentes de pressÃo e maior homogeneizaÃÃo da aeraÃÃo pulmonar, tanto na posiÃÃo supina como na prona. Houve menor hiperaeraÃÃo nas regiÃes nÃo dependentes na posiÃÃo prona, em relaÃÃo à supina, sem CPAP e com CPAP de 10 cmH2O, com melhor distribuiÃÃo da aeraÃÃo pulmonar naquela posiÃÃo. / Introduction: Noninvasive positive-pressure ventilation (NIPPV) is an effective means of treating patients with acute respiratory failure and its use has been well established in cardiogenic pulmonary edema and in exacerbations of chronic obstructive pulmonary disease (COPD), reducing the need for endotracheal intubation and improving survival. Furthermore the continuous positive airway pressure (CPAP) â a mode of NIPPV â is the recommended treatment for obstructive sleep apnea syndrome (OSAS), where frequently there is no abnormality in pulmonary parenchyma. Also in the acute respiratory distress syndrome (ARDS), the application of positive end-expiratory pressure (PEEP) may result in alveolar recruitment of nonaerated units as well as in overinflation of the aerated lung areas. Alveolar overinflation is considered an important factor related to ventilator-induced lung injury causing higher mortality. The prone position has beneficial effects on oxygenation in these patients and the additive effect of PEEP with this maneuver is debatable. High resolution computed tomography (HRCT) is an excellent imaging method to evaluate the effects of positive pressure and prone position on pulmonary parenchyma. Objectives: To evaluate the effects of CPAP applied by a nasal mask on pulmonary inflation in normal subjects in supine and prone positions. Patients and methods: This is an interventionist study that evaluated eight healthy volunteers. A protocol of HRCT of the lung was performed in three regions: at the apex (2 cm above the aortic level), hilum (1 cm below the carina) and basis (2 cm above the right diaphragm) in the supine position, without and with CPAP of 5, 10 and 15 cmH2O. Also HRCT slices were performed in the prone position at the lung basis, without and with CPAP of 10 cmH2O. All HRCT slices were obtained at the functional residual capacity. Each CPAP level was maintened at least five minutes and the period between the different levels of CPAP was similar. For analysis the results were divided into regions ventral, medial and dorsal and with slices of apex, hilum and basis together. The mean lung densities (MLD) and the percentual of units with densities lower than -950 UH (overinflated) were calculated for each region. Results: There was no difference between the MLD of apex, hilum and basis for the same level pressure. In the supine position, there were a MLD reduction and an increase of the number of pixels on hyperinflated areas according to CPAP levels: without CPAP -761 HU e 7,25%; CPAP 5: -780 HU e 8,57%; CPAP 10: -810 HU e 11,62%; CPAP 15: -828 UH e 14,65% (p< 0,05). The same occurred in the prone position without CPAP: -759 UH e 6,30% and with CPAP 10: -803 UH e 9,94% (p < 0,05). It was observed a crescent ventro-dorsal density gradient in supine position that was inverse in prone position. At CPAP of 10 cmH2O there was lower percentage of pixels on hyperinflated areas in the prone position than in supine. In the non dependent lung regions (ventral in supine and dorsal in prone) there were lower percentage of pixels on hyperinflated areas and higher on normoaerated areas in the prone position than in supine with little differences in the dependent regions. Conclusions: Non invasive CPAP in normal subjects induces progressive overdistension with increase of pressure levels in supine and prone positions. CPAP of 10 cmH2O causes less overdistension of the non dependent regions than the same level of CPAP in supine position, without inducing significant overinflation of the dependent regions. So that the prone position causes a more homogeneous air distribution through the lungs.

La queue de l’aire tegmentale ventrale (tVTA) est le principal contrôle inhibiteur des neurones dopaminergiques du mésencéphale. Cette structure, bien qu’aujourd’hui très étudiée, n’est cependant pas encore référencée dans les atlas stéréotaxiques. Anatomiquement, nous avons pu apporter une définition de référence de la tVTA, à travers son analyse neurochimique, stéréologique, hodologique et génomique. Fonctionnellement, nous avons montré son rôle dans la réponse à des expériences émotionnelles aversives et nous avons testé son influence sur les symptômes moteurs et non-moteurs de la maladie de Parkinson. Nous avons ainsi montré qu’une co-lésion de la tVTA dans un modèle murin de la maladie permet une amélioration des performances motrices, des seuils nociceptifs et des symptômes de type dépressifs. Ce travail a ainsi participé au progrès de nos connaissances sur la tVTA et ouvre de nouvelles pistes d’exploration quant à son implication fonctionnelle. / The tail of the ventral tegmental area (tVTA) is the major brake of the midbrain dopamine neurons. This structure although studied, is not yet referenced in stereotaxic atlases. Anatomically, this work allowed to obtain a reference definition of the tVTA through its neurochemical, stereological, connectivity-based and genomic analyses. Functionally, we studied its role for the response of aversive stimuli and we tested its influence on motor and non-motor symptoms of Parkinson’s disease. We observed that a co-lesion of the tVTA in a rodent model of the disease induce motor, nociceptive and depressive-like symptoms improvements. This work has thus contributed to the progress of our knowledge on the tVTA and opens new explorative track for its functional implication.

Le vieillissement de la population a vu émerger des maladies liées à l'âge telles que les maladies neurodégénératives. La neuromodulation peut être proposée à certains patients lorsque les médicaments ne sont plus efficaces ou qu'ils entraînent des effets secondaires invalidants. L’objectif de cette thèse est de mieux caractériser les structures cérébrales pour optimiser le ciblage de la neuromodulation et, ainsi augmenter les bénéfices thérapeutiques.Le premier axe de recherche porte sur la région locomotrice mésencéphalique (MLR) qui est une cible en cours d'évaluation pour les patients parkinsoniens souffrant de troubles de la marche et de l'équilibre. Nous avons exploré la connectivité de la MLR et les résultats nous ont amené à considérer que le noyau pédonculopontin (PPN), qui est une région constituante de la MLR, est la cible à privilégier. Or, une perte des neurones cholinergiques du PPN a été montrée chez les patients parkinsoniens. Le second projet a consisté à étudier la topographie de la perte de neurones chez différents groupes pathologiques. Nos résultats montrent que le maximum de densité des neurones cholinergiques se situe à +3 mm du début supérieur du PPN et serait la cible optimale de sa neuromodulation. Enfin, nous avons construit un atlas 3D du tronc cérébral humain afin de guider l’implantation d'électrode dans la MLR.Le second axe de recherche concerne le Vim qui est la cible usuelle pour les tremblements essentiels. Nous avons appliqué différentes méthodes de ciblage et comparé les localisations. Nous avons trouvé des différences de distance entre cibles, pouvant affecter les résultats de la neuromodulation, supérieures à 1.5 mm. / The aging of the population has led to the emergence of many age-related diseases such as neurodegenerative diseases. Neuromodulation techniques can be proposed to some patients when medications are no longer effective or have invalidating side effects. The objective of this PhD is to better characterize brain structures in order to optimize neuromodulation targeting and thus increase the therapeutic benefits for patients.The first area of research concerns the mesencephalic locomotor region (MLR), which is a neuromodulation target being evaluated for Parkinsonian patients who suffer from walking and balance disorders. We explored the anatomical connectivity of the MLR and the results led us to consider the pedonculopontin nucleus (PPN), which is a part of the MLR, as the target of neuromodulation to privilege. However, partial loss of cholinergic neurons in the PPN has been shown in Parkinsonian patients. The second project consisted in studying the topography of this loss in different pathological groups. Our results show that the maximum density of cholinergic neurons in all the subjects is situated at +3 mm from the superior edge of the PPN and is the optimal target for its neuromodulation. Finally, we constructed a 3D atlas of the healthy human brainstem in order to guide the implantation of electrodes in the MLR.The second area of research concerns the ventral intermediate nucleus (Vim) of the thalamus, which is the usual neuromodulation target for essential tremors. We applied various targeting methods of the Vim and compared the locations. We found differences in distance between targets greater than 1.5 mm which may affect the neuromodulation results.

Le syndrome de détresse respiratoire aiguë (SDRA) est caractérisé par des lésions alvéolairesdiffuses qui résultent d'une lésion de la membrane alvéolo-capillaire entrainant entre autresune réaction inflammatoire intense et une perte massive et hétérogène du volume pulmonaireaéré. La tomographie par émission de positons (TEP) et la tomographie par impédanceélectrique (TIE) sont deux techniques d'imagerie fonctionnelle permettant l'étude noninvasive, quantitative et régionale du poumon.Ce travail présente le résultat d'études expérimentales conduites dans le SDRA. Tout d'abord,nous avons comparé positivement la TIE à la TEP pour la mesure de la ventilation pulmonaireet du volume aéré. Nous avons ensuite décrit et validé une technique robuste d'obtention duvolume aéré et de la ventilation spécifique en TEP sans prélèvement invasif. Enfin, nousavons étudié en TEP l'influence de la pression expiratoire positive (PEP) et du décubitusventral (DV) sur la répartition de la ventilation, de la perfusion et de l'inflammationpulmonaires. Les poumons agressés par l'acide chlorhydrique inhalé ont une inflammationsignificativement plus élevée que le groupe contrôle. Aucune différence significatived'inflammation n'a été trouvée entre les groupes expérimentaux malgré des modificationsimportantes de la répartition de la ventilation et de la perfusion régionales lors de la mise enDV. Ces études donc ont permis le développement d'un modèle porcin stable d'agressionpulmonaire aiguë et la validation de techniques d'imagerie permettant l'étude non invasive deparamètres physiologiques importants pouvant aider au réglage de la ventilation mécanique aucours du SDRA.

We have previously shown that the arcuate organization of cell fates within the ventral midbrain critically depends upon the morphogen, Sonic Hedgehog (SHH), which is secreted from a signaling center located along the ventral midline, called the floor plate (FP). Thus, it is ultimately the specification of the FP that is responsible for the patterning and specification of ventral midbrain cell fates. Interestingly, we have found that the chick midbrain FP can be divided into medial (MFP) and lateral (LFP) regions on the basis of gene expression, mode of induction and function. Overexpression of SHH alone is sufficient to recapitulate the entire pattern of ventral cell fates, although remarkably it cannot induce MFP, consistent with the observation that the MFP is refractory to any perturbations of HH signaling. In contrast, overexpression of the winged-helix transcription factor FOXA2/HNF3[beta]robustly induced the MFP fate throughout ventral midbrain while blocking its activity resulted in the absence of the MFP. Thus, by analyzing the differences between SHH and FOXA2 blockade and overexpression, we were able to attribute functions to each the LFP and the MFP. Notably, we observed that FOXA2 overexpression caused a bending of the midbrain neurepithelium that resembled the endogenous median hinge-point observed during neurulation. Additionally, FOXA2 misexpression led to a robust induction of DA progenitors and neurons that was never observed after SHH expression alone. In contrast, we found that all other ventral cell types required HH signaling directly, at a distance and early on in the development of the midbrain when its tissue size is relatively small. Additionally, HH blockade resulted in increased cell-scatter of the arcuate territories and in the disruption of the regional boundaries between the ventral midbrain and adjacent tissue. Thus, we bring new insight into the mechanism by which midbrain FP is specified and ascribe functional roles to its subregions. We propose that while the MFP regulates the production of dopaminergic progenitors and the changes in cellshape required for bending and shaping the neural tube, the LFP appears to be largely responsible for cell survival and the formation of a spatially coherent pattern of midbrain cell fates. / text

Η ΒΥΠ διαθέτει αντίτυπο της διατριβής σε έντυπη μορφή στο βιβλιοστάσιο διδακτορικών διατριβών που βρίσκεται στο ισόγειο του κτιρίου της. / Ο ιππόκαμπος στον αρουραίο είναι μια δομή σε C-σχήμα που εκτείνεται από τον διαφραγματικό πυρήνα προσθιοραχιαία έως τον κροταφικό λοβό οπισθιοκοιλιακά. Παρόλο που από παλιά θεωρείτο ως ομοιογενής δομή, έχουν παρατηρηθεί πολλές διαφορές σε όλα τα επίπεδα οργάνωσης μεταξύ του διαφραγματικού και του κροταφικού ιππόκαμπου. Οι βενζοδιαζεπίνες δρουν στις θέσεις δέσμευσης των βενζοδιαζεπινών, οι οποίες είναι αλλοστερικά συνδεδεμένες με το σύμπλοκο του GABAA, όπου ενισχύουν την δράση του GABA στους GABAA υποδοχείς, αυξάνοντας τη συχνότητα ανοίγματος του διαύλου των ιόντων χλωρίου (Cl-) και έχοντας μικρή μόνο επίδραση στο χρόνο ανοίγματος ή στην αγωγιμότητα του διαύλου. Προηγούμενη μελέτη υποδεικνύει ότι η έκφραση των α1-, β2- και γ2-υπομονάδων ήταν μικρότερη, ενώ αντίθετα η έκφραση των α2-, α5- και β1-υπομονάδων ήταν μεγαλύτερη στον κροταφικό ιπποκάμπο σε σύγκριση με τον διαφραγματικό ιππόκαμπο. Σύμφωνα με προηγούμενες μελέτες που αφορούν την συνέκφραση των υπομονάδων στο σύμπλοκο του GABAA υποδοχέα τα αποτελέσματα μας υποδηλώνουν ότι ο α1β2-υποτύπος του GABAA υποδοχέα επικρατεί στον διαφραγματικό ιππόκαμπο (ΔΙ), ενώ ο α2β1-υπότυπος κυριαρχεί στον κροταφικό ιππόκαμπο (ΚΙ). Επιπλέον, φαρμακολογικές μελέτες έχουν δείξει ότι η καταπραϋντική δράση της diazepam πραγματοποιείται μέσω των GABAA υποδοχέων, που περιέχουν την α1-υπομονάδα, ενώ η αγχολυτική δράση της πραγματοποιείται μέσω των υποδοχέων που φέρουν την α2-υπομονάδα. Επομένως, η μελέτη των φαρμακολογικών ιδιοτήτων των υποτύπων του GABAΑ υποδοχέα δίνει την δυνατότητα στο να σχεδιαστούν ειδικά φάρμακα τα οποία θα βελτιώνουν το κλινικό προφίλ ασθενειών, όπως το άγχος, η αϋπνία ή η επιληψία, δρώντας σε εξειδικευμένους υποτύπους του GABAΑ υποδοχέα. Ο στόχος της συγκεκριμένης εργασίας ήταν να μελετηθούν οι φαρμακολογικές ιδιότητες των υποτύπων του συμπλόκου του GABAA υποδοχέα/βενζοδιαζεπινών στον διαφραγματικό σε σύγκριση με τον κροταφικό ιππόκαμπο επίμυος. Έτσι, για τη μελέτη των θέσεων δέσμευσης των βενζοδιαζεπινών μεταξύ του διαφραγματικού και κροταφικού ιπποκάμπου χρησιμοποιήθηκε ο ευρέως φάσματος αγωνιστής των θέσεων δέσμευσης των βενζοδιαζεπινών, [3H]-flunitrazepam, σε μια αυτοραδιογραφική μελέτη. Επιπλέον, χρησιμοποιήθηκαν εξειδικευμένα φάρμακα, που δεσμεύονται σε συγκεριμένους υποτύπους του GABAA υποδοχέα, όπως το zolpidem (ειδικός αγωνιστής των GABAA υποδοχέων, που περιέχουν την α1-υπομονάδα), το etomidate (ειδικός θετικός αλλοστερικός ρυθμιστής των GABAA υποδοχέων, που περιέχουν τη β2-υπομονάδα) και το L-655,708 (ειδικός αντίστροφος αγωνιστής των GABAA υποδοχέων, που περιεχούν την α5-υπομονάδα) σε μια αυτοραδιγραφική κινητική μελέτη. Τα αποτελέσματα μας έδειξαν ότι οι τομές που προέρχονταν από τον ΚΙ συγκρινόμενες με αυτές από τον ΔΙ είχαν: Α) μειωμένη δέσμευση της [3H]-flunitrazepam στις CA1, CA3 και DG περιοχές, Β) μικρότερη χημική συγγένεια της δέσμευση της [3H]-flunitrazepam στη CA1 περιοχή, Γ) καμία διαφορά στον αριθμό των θέσεων δέσμευσης, Δ) μεγαλύτερες τιμές IC50 και EC50 για το zolpidem και το etomidate, αντίστοιχα και Ε) μικρότερες τιμές IC50 για το L-655,708. Συμπερασματικά, τα αποτελέσματά μας υποδεικνύουν διαφορετικές φαραμκολογικές ιδιότητες των υποτύπων του GABAΑ/ΒΖ υποδοχέα μεταξύ του ΔΙ και ΚΙ, ενώ επιβεβαιώνεται και ενισχύεται προηγούμενη μελέτη που υποδηλώνει ότι ο α1β2-υποτύπος του GABAA υποδοχέα επικρατεί στον διαφραγματικό ιππόκαμπο (ΔΙ), ενώ ο α2β1-υπότυπος κυριαρχεί στον κροταφικό ιππόκαμπο (ΚΙ). Η μελέτη αυτή είναι πιθανό να τυγχάνει ιδιαίτερης κλινικής αξίας, στην κατεύθυνση της ακριβέστερης ρύθμισης των αποτελεσματικών δόσεων των διάφορων μορίων που δρουν στις θέσεις δέσμευσης των βενζοδιαζεπινών των α1- και α2-υποτύπων του GABAA υποδοχέα. / The hippocampus in the rat appears grossly as an elongated structure with its long axis bending in a C-shaped manner from the septal nuclei rostrodorsally to the incipient temporal lobe caudoventrally. The long axis of the hippocampal formation is referred as the dorsoventral axis. Although hippocampus has been traditionally thought as a homogeneous structure, several studies have been demonstrated differences at several organization levels (from the behavioural to the cellular) between its dorsal (DH) and ventral (VH) pole. Pharmacological studies have shown that the α1-GABAA receptor subtype is associated with the sedative and anticonvulsant effects of benzodiazepines (BZs), whereas the α2-subtype is associated with the anxiolytic effects of BZs. Recent data have demonstrated a differential distribution of the GABAA receptor subunits between DH and VH, with the α1/β2 GABAA receptor subtype dominating in the DH and the α2/β1 subtype prevailing in the VH. We therefore study possible differences in the pharmacological properties and receptor binding parameters of the GABAA/BZ receptor subtypes between DH and VH, by examining: 1a) the specific binding of [3H]-flunitrazepam (BZ sites agonist), by using quantitative autoradiography, b) the kinetic parameters of [3H]-flunitrazepam specific binding, by using the “wipe off” technique and 2) the competitive displacement of [3H]-flunitrazepam binding by using zolpidem (a specific agonist of α1-subtype) and L-655,708 (a specific inverse agonist of α5-subtype) and the enhancement of [3H]-flunitrazepam binding by using etomidate (a selective positive modulator of β2- subunit), in an autoradiographical saturation kinetic study. Our results showed in VH compared to the DH: A) lower level of [3H]-flunitrazepam binding in CA1, CA3 and DG regions, B) higher KD value for [3H]-flunitrazepam specific binding in CA1 region and no differences in the Bmax value, C) higher IC50 and EC50 values for zolpidem and etomidate, respectively and D) lower IC50 values for L-655,708. In conclusion, the lower affinity of GABAA receptors for [3H]-flunitrazepam binding, the higher IC50 and EC50 values for zolpidem and etomidate, respectively, as well as the lower IC50 values for L-655,708 observed in VH compared to DH, support the evidence that the α1/β2-GABAA receptor subtype dominates in DH and the α2/β1-subtype prevails in VH and suggest differential pharmacological effects of the benzodiazepines in DH compared to VH, which could be of clinical relevence for the more accuate adjustment of the effective dose of α1- and α2-subtype specific BZ binding sites’ ligands.

This work aims at studing the role of tachykinin NK-3 receptor (R) and kinin B1R in central autonomic regulation of blood pressure (BP) and to determine whether the B1R is overexpressed and functional in rat models of hypertension by measuring the effect of a B1R agonist on behavioural activity. Assumptions: (1) NK-3R located in the ventral tegmental area (VTA) modulates the mesolimbic dopaminergic system and has a tonic activity in hypertension; (2) B1R is overexpressed in the brain of hypertensive rats and has a tonic activity, which contributes to hypertension via a dopamine mechanism; (3) the inhibition of NK-3R and B1R with selective antagonists, reduces central dopaminergic hyperactivity and reverses hypertension. A model of genetic hypertension and a model of experimental hypertension were used: spontaneously hypertensive rats (SHR, 16 weeks) and Wistar-Kyoto (WKY) rats infused for 14 days with angiotensin II (Ang II) (200 ng / kg / min, subcutaneous (s.c.) with Alzet mini pump). The age-matched untreated WKY rats served as common controls. In the first study (article # 1), the cardiovascular response in SHR was evaluated following intracebroventricular (i.c.v.) and/or intra-VTA injection of an agonist (senktide) and antagonists (SB222200 and R-820) of NK-3R. These responses have also been characterized using selective dopamine antagonists DA-D1R (SCH23390), DA-D2R (raclopride) or non-selective dopamine DA-D2R (haloperidol). Also the VTA has been destroyed by ibotenic acid. The pressor response induced by senktide and the anti-hypertensive response induced by SB222200 or R-820 were more pronounced by intra-VTA. These responses were prevented by pre-treatment with raclopride and haloperidol. The lesion of the VTA has prevented the pressor response relayed by senktide (i.c.v.) and the anti-hypertensive effect of R-820 (i.c.v.). In addition, SB222200 (intra-VTA) prevented the pressor response of senktide (i.c.v.) and conversely, senktide (i.c.v.) prevented the antihypertensive effect of SB222200 (intra-VTA). The second study (article # 2) showed that the B1R antagonist (SSR240612) administered by gavage or i.c.v. reverses hypertension in both models. This anti-hypertensive effect was prevented by raclopride and haloperidol. In contrast, the two B1R antagonists (R-715 and R-954) injected s.c., which do not cross the blood-brain barrier reduced weakly blood pressure in hypertensive rats. In the third study (article # 3), the i.c.v. injection of a selective kinin B1R agonist Sar[DPhe8][des-Arg9]BK caused behavioural responses in SHR and Ang II-treated rats and had no effect in control WKY rats . The responses elicited by B1R agonist were blocked by an antagonist of NK-1 (RP67580), an antagonist of NMDA glutamate receptor (DL-AP5), an inhibitor of nitric oxide synthase (NOS) (L -NNA) as well as raclopride and SCH23390.The responses were modestly affected by the inhibitor of inducible NOS (iNOS). The B1R mRNA (measured by RT-PCR) was significantly increased in the hypothalamus, the VTA and the nucleus accumbens of hypertensive animals (SHR and treated with Ang II) compared with control rats. These neuropharmacological studies suggest that: (1) the NK-3R from the VTA is involved in the maintenance of hypertension in SHR by increasing DA transmission in the midbrain; (2) the B1R in SHR and Ang II-treated rats contributes to hypertension via a central mechanism involving DA-D2R; (3) the central B1R increases locomotor activity and nocifensive behaviours via the release of substance P (NK-1), DA and nitric oxide in both rat models of hypertension. Thus, the brain tachykinin NK-3R and kinin B1R represent potential therapeutic targets for the treatment of hypertension. The modulation of the mesolimbic/mesocortical dopaminergic pathway by these receptors suggests their involvement in other physiological functions (pleasure, motor activity, coordination of the response to stress) and pathophysiology (anxiety, depression). / Ce travail vise à étudier le rôle du récepteur NK-3 des tachykinines (NK-3R) et du récepteur B1 des kinines (B1R) dans la régulation autonomique centrale de la pression artérielle et de déterminer si le B1R est surexprimé et fonctionnel chez le rat hypertendu en mesurant l’effet d’antagoniste B1R sur l’activité comportementale. Hypothèses: (1) le NK-3R localisé dans l’aire tegmentale ventrale (VTA) module l’activité dopaminergique du système mésolimbique et possède une activité tonique dans l’hypertension; (2) le B1R est surexprimé dans le cerveau du rat hypertendu et possède une activité tonique qui contribue à l’hypertension via un mécanisme dopaminergique; (3) l’inhibition des NK-3R et B1R avec des antagonistes sélectifs réduit l’hyperactivité dopaminergique centrale et renverse l’hypertension. Un modèle d’hypertension génétique et un modèle d’hypertension expérimentale ont été utilisés: le rat spontanément hypertendu (SHR, 16 sem) et le rat Wistar Kyoto (WKY) infusé pendant 14 jours avec l’angiotensine II (Ang II) (200 ng/kg/min, s.c. avec mini pompe Alzet). Le rat WKY non traité du même âge a servi de témoin commun. Dans la première étude (article # 1), la réponse cardiovasculaire des SHR a été évaluée à la suite de l’injection i.c.v. et/ou intra-VTA d’un agoniste (senktide) et d’antagonistes (SB222200 et R-820) du NK-3R. Ces réponses ont aussi été caractérisées en utilisant des antagonistes sélectifs des récepteurs DA-D1R (SCH23390), DA-D2R (raclopride) ou non-sélectif DA-D2R (halopéridol). Aussi le VTA a été détruit par l’acide iboténique. La réponse pressive induite par senktide et la réponse anti-hypertensive induite par SB222200 ou R-820 étaient plus marquées par la voie intra-VTA. Ces réponses ont été prévenues par un pré-traitement avec le raclopride et l’halopéridol. La lésion du VTA a prévenu la réponse pressive relayée par le senktide (i.c.v.) ainsi que l’effet anti-hypertenseur du R-820 (i.c.v.). De plus, le SB222200 (intra-VTA) a prévenu la réponse pressive du senktide (i.c.v.) et inversement, le senktide (i.c.v.) a prévenu l’effet anti-hypertenseur du SB222200 (intra-VTA). La deuxième étude (article # 2) a montré que l’antagoniste du B1R (SSR240612) administré par gavage ou i.c.v. renverse l’hypertension artérielle dans les deux modèles. Cet effet dépresseur a été prévenu par le raclopride ainsi que l’halopéridol. Par contre, le traitement avec deux antagonistes du B1R (R-715 et R-954) qui ne traversent pas la barrière hémo-encéphalique a réduit faiblement la pression artérielle chez les rats hypertendus. Dans la troisième étude (article # 3), l’injection i.c.v. d’un agoniste sélectif du B1R, le Sar[DPhe8][des-Arg9]BK a causé des réponses comportementales typiques chez le SHR et le rat traité à l’Ang II mais il n’a pas eu d’effet chez le rat témoin WKY. Les réponses induites par l’agoniste B1R ont été bloquées par un antagoniste du récepteur NK-1(RP67580), un antagoniste du récepteur NMDA du glutamate (DL-AP5), un inhibiteur des synthétases du monoxyde d’azote (NOS) (L-NNA) ainsi qu’avec le raclopride et le SCH23390. Les réponses ont été modestement influencées par l’inhibiteur de la NOS inductible (iNOS). L’ARNm du B1R (mesuré par RT-PCR) était significativement augmenté dans l’hypothalamus, le VTA et le noyau accumbens des animaux hypertendus (SHR et traités à l’Ang II) comparativement aux rats témoins. Ces études neuropharmacologiques suggèrent : (1) que le NK-3R du VTA est impliqué dans le maintien de l’hypertension chez le SHR en augmentant la transmission DA au niveau du mésenséphale. (2) Le B1R chez le SHR et les rats traités à l’Ang II contribue à l’hypertension artérielle via un mécanisme central impliquant le DA-D2R. (3) le B1R central augmente l’activité locomotrice et les comportements défensifs, via la relâche de substance P (NK-1), de DA et de NO dans un modèle d’hypertension génétique et expérimental chez le rat. Ainsi, les récepteurs cérébraux NK-3 des tachykinines et B1 des kinines représentent des cibles thérapeutiques potentielles pour le traitement de l’hypertension artérielle. La modulation de la voie dopaminergique mésolimbique/mésocorticale par ces récepteurs suggère une participation dans d’autres fonctions physiologiques (plaisir, activité motrice, coordination de la réponse au stress) et en pathophysiologie (anxiété, dépression).

Central to human intelligence, visual categorization is a skill that is both remarkably fast and accurate. Although there have been numerous studies in primates regarding how information flows in inferiortemporal (ITC) and prefrontal (PFC) cortices during online discrimination of visual categories, there has been little comparable research on the human cortex. To bridge this gap, this thesis explores how visual categories emerge in prefrontal cortex and the ventral stream, which is the human homologue of ITC. In particular, cortical spatiotemporal plasticity in visual category learning was investigated using behavioral experiments, magnetoencephalographic (MEG) imaging, and statistical machine learning methods. From a theoretical perspective, scientists from work on non-human primates have posited that PFC plays a primary role in the encoding of visual categories. Much of the extant research in the cognitive neuroscience literature, however, emphasizes the role of the ventral stream. Despite their apparent incompatibility, no study has evaluated these theories in the human cortex by examining the roles of the ventral stream and PFC in online discrimination and acquisition of visual categories. To address this question, I conducted two learning experiments using visually-similar categories as stimuli and recorded cortical response using MEG—a neuroimaging technique that offers a millisecond temporal resolution. Across both experiments, categorical information was found to be available during the period of cortical activity. Moreover, late in the learning process, this information is supplied increasingly in the ventral stream but less so in prefrontal cortex. These findings extend previous theories by suggesting that the ventral stream is crucial to long-term encoding of visual categories when categorical perception is proficient, but that PFC jointly encodes visual categories early on during learning. From a methodological perspective, MEG is limited as a technique because it can lead to false discoveries in a large number of spatiotemporal regions of interest (ROIs) and, typically, can only coarsely reconstruct the spatial locations of cortical responses. To address the first problem, I developed an excursion algorithm that identified ROIs contiguous in time and space. I then used a permutation test to measure the global statistical significance of the ROIs. To address the second problem, I developed a method that incorporates domainspecific and experimental knowledge in the modeling process. Utilizing faces as a model category, I used a predefined “face” network to constrain the estimation of cortical activities by applying differential shrinkages to regions within and outside this network. I proposed and implemented a trial-partitioning approach which uses trials in the midst of learning for model estimation. Importantly, this renders localizing trials more precise in both the initial and final phases of learning. In summary, this thesis makes two significant contributions. First, it methodologically improves the way we can characterize the spatiotemporal properties of the human cortex using MEG. Second, it provides a combined theory of visual category learning by incorporating the large time scales that encompass the course of the learning.