Afin d'avancer sur la fonction du sommeil paradoxal, il est nécessaire d'étudier son impact sur le fonctionnement cortical. Nous avons ainsi comparé l'expression génique corticale à l'aide de puces à ADN chez trois groupes de rats présentant différentes quantités de sommeil paradoxal (SP) : témoins, privé de SP ou en hypersomnie de SP. 71 et 83 transcrits montrent un niveau d'expression modifié par notre protocole dans le néocortex et l'hippocampe, respectivement. Ces résultats moléculaires ont été confirmés par PCR quantitative. Dans l'hippocampe l'expression des gènes de plasticité (Fos, Arc, Cox2, Homer1...) augmente en hypersomnie de SP. Au contraire, dans le néocortex le niveau d'expression de ces gènes augmente après privation de SP. Au niveau systémique, les aires limbiques (le gyrus dentelé, le cortex cingulé antérieur et rétrosplénial et le claustrum) contiennent un nombre de neurones immunoréactifs au FOS, un marqueur d'activation indirect, élevé après hypersomnie de sommeil paradoxal. En revanche, le nombre de neurones immunoréactifs au FOS dans les cortex sensoriels est diminué après hypersomnie par rapport à la privation de sommeil paradoxal L'éjection de traceurs rétrogrades dans le gyrus dentelé, le cortex rétrosplénial et le cortex cingulaire antérieur des rats en hypersomnie de SP a permis d'observer des neurones afférents et actifs dans les noyaux supramamillaires et le claustrum. Nous avons ensuite observé que le nombre de neurones immunoréactifs pour FOS, ARC dans le gyrus dentelé, le claustrum et certaines structures limbiques est fortement diminué pendant l'hypersomnie de SP chez des rats porteurs d'une lésion des noyaux supramamillaires. De plus, la lésion du Sum est accompagnée d'une diminution de la puissance du thêta enregistrée par l'électroencéphalogramme pendant le sommeil paradoxal en hypersomnie. Il semble donc que les projections des noyaux supramamillaires soient responsables de l'activation des régions limbiques corticales pendant le SP / To move forward on the PS function, it is necessary to study its impact on the cortical functioning. We so compared the cortical genic expression by using DNA microarrays in three groups of rats with different PS amounts: control, deprived of PS and in PS hypersomnia. 71 and 83 transcripts have an expression level modified by our protocol in the neocortex and the hippocampal formation, respectively. These molecular results were confirmed by quantitative PCR. In the hippocampal formation the genes involved in synaptic plasticity (Fos, Arc, Cox2, Homer1) have an expression level increased after PS hypersomnia. In the contrary, in the neocortex the expression level of these genes increases after PS deprivation. At the systemic level, limbic areas (the dentate gyrus, anterior cingulate and retrosplenial cortex and claustrum) contain a number of FOS immunoreactive neurons, an indirect marker of neuronal activation, increased after PS hypersomnia. On the other hand, the number of FOS immunoreactive neurons in the sensory-motor cortices is decreased after PS hypersomnia compare to PS deprivation. The ejection of retrograde tracers in the dentate gyrus, retrosplenial and anterior cingulate cortex in PS hypersomniac rats showed that active neurons project to the supramammillary nucleus and claustrum. We then observed that the number of FOS and ARC immunoreactive neurons in the dentate gyrus, claustrum and limbic structures is strongly decreased during PS hypersomnia in rats bearing a supramammillary nucleus lesion. Furthermore, the supramammillary nucleus lesion leads to a decrease of the theta power recorded by electroencephalogram during PS in hypersomnia. It thus seems that the supramammillary nucleus projections are responsible for the limbic cortical regions activation during PS

Cette recherche se situe au croisement de quatre domaines différents : la didactique du FOS ; l’analyse de discours ; l’autonomisation de l’apprenant et l’apprentissage sur le web. Nous avons recueilli un corpus qui nous a fourni des données permettant de concevoir des activités discursives et contextualisées exploitant le web (web-based learning, web comme outil de communication, web comme artéfact intégrant dans l’environnement d’apprentissage) pour l’apprentissage du français dans le cadre du FOS – tourisme. Nous avons choisi de mettre l’accent sur l’activité discursive parce qu’elle nous permet de répondre à deux questions : - que faut-il enseigner/apprendre dans un contexte du FOS du tourisme ? - quelles sont les caractéristiques des discours impliqués ? Notre corpus comporte deux guides imprimés sur le Vietnam (environ 1000 pages) et le discours oral des guides touristiques transcrit à partir des enregistrements dont la durée totale est d’environ 10 heures continues. Il s’agit donc à la fois de l’extraction de données dans le corpus, du transfert de ces données à la didactique et de leur réutilisation directe dans la conception des activités d’apprentissage. Le transfert consiste en l’application des conclusions tirées de l’analyse du corpus pour l’élaboration des activités discursives tandis que la réutilisation de ces données consiste en d’extractions des éléments du corpus pour les intégrer aux activités discursives. Pour analyser le corpus et pour structurer, programmer les activités discursives, nous avons fait appel au langage XML et conçu des scripts informatiques permettant son exploitation (analyse et activités d’apprentissage). Enfin, notre recherche débouche sur une perspective didactique. Nous recommandons la démarche discursive pour la conception d’un programme de formation et d’activités discursives. Nous illustrons cette démarche par des activités d’apprentissage concrètes. Il est à noter que s’il agit d’une étude exploratoire et non expérimentale. / This research lies at the intersection of four different areas: French for specific purposes; discourse analysis; learner autonomy and web based learning. We’ve collected a corpus which provided data for designing contextualized discursive activities exploiting the web (web-based learning : web as a communication tool, web as artifact integrated into the learning environment ) in the context of FOS for tourism. We chose to focus on the discursive activity because it allows us to answer two questions: - What should be taught / learned in a context of FOS for tourism ? - What are the characteristics of speech involved ? Our corpus comprises two printed travel guides on Vietnam (approximately 1000 pages) and oral discourse transcribed from records of tour guide speeches (about 10 hours in total). It is therefore both data mining in the corpus, the transfer of this data for applied linguistic and their direct reuse in the design of learning activities. The transfer is the application of the conclusions drawn from the analysis of the corpus for the development of discursive activities while the reuse of these data consists in extracting corpus elements to integrate them into discursive activities. To analyze the corpus, to structure and to program discursive activities, we used the XML and developed scripts for computer operations (analysis and learning activities ). Finally, our research leads to a didactic perspective. We recommend the discursive approach for the design of syllabus and discursive learning activities. We illustrate this approach with some learning activities. It should be noted that this is an exploratory study and not an experimental one.

As células Y-1 pertencem a uma linhagem clonal de células funcionais de córtex adrenal de camundongo, que respondem a ACTH. Em células Y-1, ACTH promove a esteroidogênese (função) e tem efeitos regulatórios complexos na transição G0→G1→S do ciclo celular. ACTH promove a transição G0→G1, mas inibe a transição G1→S. É possível que a regulação do ciclo celular por ACTH seja mediada pelo controle da expressão dos proto-oncogenes das famílias fos, jun e myc. Nosso laboratório mostrou, anteriormente, que ACTH induz a expressão dos genes fos e jun, mas inibe c-myc. O objetivo deste trabalho foi identificar pontos de controle na expressão dos genes fos, jun e myc e na atividade dos fatores de transcrição AP-1 (dímeros da proteínas Fos e Jun) por ACTH, derivados de cAMP (ativadores de PKA), PMA (ativador de PKC) e FCS (soro fetal bovino). ACTH, PMA e dcAMP aumentam a atividade de ligação de AP-1 a DNA, independentemente de síntese protéica. Ensaios de elongação de cadeia nascente de RNA (run off transcription) mostram que ACTH, PMA e FCS são fortes indutores de c-fos, c-jun e junB, enquanto dcAMP induz apenas c-fos e junB. Hibridizações Northern permitiram estimar a meia-vida dos mRNAs de c-fos e c-jun em 30 min, independentemente do tratamento com ACTH ou PMA. Diferentemente de c-fos, o mRNA de fosB é superinduzido por ActinomicinaD em células Y-1 tratadas com ACTH e PMA. / The Y-1 cells belong to a clonal lineage of functional mouse adrenocortical cells, which are responsive to ACTH. In Y-1 cells, ACTH promotes esteroidogenesis (function) and has complex effects on the G0→G1→S transition of the Y-1 cell cycle. ACTH induces the G0→G1 transition but inhibits the G1+S transition. Probably, the cell cycle regulation by ACTH is mediated by the expression control of the proto-oncogenes from the fos, jun and myc families. Our laboratory has previously shown that ACTH induces the fos and jun genes expression, but inhibits c-myc expression. The target of this work was to identify control points in the fos, jun and myc genes expression and in the AP-1 transcription factors (Fos and Jun proteins dimers) by ACTH, cAMP derivatives (PKA activators), PMA (PKC activator) and FCS (Fetal Calf Serum). ACTH, PMA and dcAMP raise the AP-1 DNA binding activity, independently of protein synthesis. Run off transcription assays show that ACTH, PMA and FCS are strong c-fos, c-jun and junB inducers, while dcAMP induces only c-fos and junB. Northern hybridisations allowed us to estimate the half life of the fos and jun mRNAs in about 30 min, independently of ACTH or PMA treatment. Differently of c-fos, fosB mRNA is superinduced by ActinomicinD treatment in Y-1 cells treated with ACTH or PMA.

La navigation spatiale est une fonction complexe qui nécessite de combiner des informations sur l’environnement et notre mouvement propre pour construire une représentation du monde et trouver le chemin le plus direct vers notre but. Cette intégration multimodale suggère qu’un large réseau de structures corticales et sous-corticales interagit avec l’hippocampe, structure clé de la navigation. Je me suis concentrée chez la souris sur la navigation de type séquence (ou stratégie égocentrique séquentielle) qui repose sur l’organisation temporelle de mouvements associés à des points de choix spatialement distincts. Après avoir montré que l’apprentissage de cette navigation de type séquence nécessitait l’hippocampe et le striatum dorso-médian, nous avons caractérisé le réseau fonctionnel la sous-tendant en combinant de l’imagerie Fos, de l’analyse de connectivité fonctionnelle et une approche computationnelle. Les réseaux fonctionnels changent au cours de l’apprentissage. Lors de la phase précoce, le réseau impliqué comprend un ensemble de régions cortico-striatales fortement corrélées. L’hippocampe était activé ainsi que des structures impliquées dans le traitement d’informations de mouvement propre (cervelet), dans la manipulation de représentations mentales de l’espace (cortex rétrosplénial, pariétal, entorhinal) et dans la planification de trajectoires dirigées vers un but (boucle cortex préfrontal-ganglions de la base). Le réseau de la phase tardive est caractérisé par l’apparition d’activations coordonnées de l’hippocampe et du cervelet avec le reste du réseau. Parallèlement, nous avons testé si l’intégration de chemin, de l’apprentissage par renforcement basé modèle ou non-basé modèle pouvaient reproduire le comportement des souris. Seul un apprentissage par renforcement non-basé modèle auquel une mémoire rétrospective était ajoutée pouvait reproduire les dynamiques d’apprentissage à l’échelle du groupe ainsi que la variabilité individuelle. Ces résultats suggèrent qu’un modèle d’apprentissage par renforcement suffit à l’apprentissage de la navigation de type séquence et que l’ensemble des structures que cet apprentissage requiert adaptent leurs interactions fonctionnelles au cours de l’apprentissage. / Spatial navigation is a complex function requiring the combination of external and self-motion cues to build a coherent representation of the external world and drive optimal behaviour directed towards a goal. This multimodal integration suggests that a large network of cortical and subcortical structures interacts with the hippocampus, a key structure in navigation. I have studied navigation in mice through this global approach and have focused on one particular type of navigation, which consists in remembering a sequence of turns, named sequence-based navigation or sequential egocentric strategy. This navigation specifically relies on the temporal organization of movements at spatially distinct choice points. We first showed that sequence-based navigation learning required the hippocampus and the dorsomedial striatum. Our aim was to identify the functional network underlying sequence-based navigation using Fos imaging and computational approaches. The functional networks dynamically changed across early and late learning stages. The early stage network was dominated by a highly inter-connected cortico-striatal cluster. The hippocampus was activated alongside structures known to be involved in self-motion processing (cerebellar cortices), in mental representation of space manipulations (retrosplenial, parietal, entorhinal cortices) and in goal-directed path planning (prefrontal-basal ganglia loop). The late stage was characterized by the emergence of correlated activity between the hippocampus, the cerebellum and the cortico-striatal structures. Conjointly, we explored whether path integration, model-based or model-free reinforcement learning algorithms could explain mice’s learning dynamics. Only the model-free system, as long as a retrospective memory component was added to it, was able to reproduce both the group learning dynamics and the individual variability observed in the mice. These results suggest that a unique model-free reinforcement learning algorithm was sufficient to learn sequence-based navigation and that the multiple structures this learning required adapted their functional interactions across learning.

Master of Science / Department of Psychology / Mary E. Cain / Previous research has shown that both the environment and psychostimulant use influence dopamine levels via the mesolimbic dopamine pathway. C-fos expression has also been observed following exposure to novel environments and psychostimulants. The present study looked to determine the effects of acute amphetamine exposure on locomotor activity and c-fos expression in the basolateral and central nucleus of the amygdala, for rats raised in either an enriched condition (EC), impoverished condition (IC), or social condition (SC). Rats were reared in either the EC, IC, or SC for 30 days, after which they received an acute amphetamine injection (1.0 mg/kg) and locomotor activity was measured. Following the locomotor test rats were perfused and immunohistochemistry was used to measure c-fos levels in the basolateral and central nucleus of the amygdala. Results showed that EC amphetamine rats had significantly greater locomotor activity compared to EC saline rats. There were no significant group or treatment differences in c-fos expression in the ACe. In the BLA SC amphetamine rats had significantly greater c-fos expression than EC amphetamine rats. Overall, the current study revealed that environmental enrichment and amphetamine do significantly alter locomotor activity and c-fos expression in the BLA.

Les mécanismes neurologiques responsables du déclenchement et de l'homéostasie du sommeil, et du sommeil paradoxal (SP) en particulier, sont l'objet d'un nombre toujours plus important d'études du fait notamment de l'attention croissante portée aux pathologies associées. Les travaux rapportés dans cette thèse s'inscrivent parfaitement dans cette dynamique puisqu'ils ont pour objectif de mieux caractériser les populations neuronales mises en jeu dans la régulation du SP ainsi que leurs interactions. Dans cette optique, nous avons combiné différentes approches techniques complémentaires à savoir : neuroanatomie fonctionnelle, polysomnographie et pharmacologie sur animal libre de se mouvoir. Nous avons ainsi pu démontrer pour la première fois la nature glutamatergique des neurones du SLD, région pontique jouant un rôle central dans la mise en place du SP. De plus, s'il est généralement admis que ces neurones du SLD sont sous le contrôle de neurones GABAergiques situés au niveau de la partie ventrolatérale de la substance grise périaqueducale (VLPAG), le contrôle de ces derniers est encore soumis à controverse. Les résultats que nous avons obtenus suggèrent fortement que l'aire latérale de l'hypothalamus (LH) serait responsable de ce contrôle et donc de celui du SP. En effet, la LH est l'afférence majeure à la VLPAG activée lors d'une hypersomnie de SP. En outre, son inactivation par application locale de muscimol entraine la disparition totale du SP et l'activation des neurones GABAergiques de la VLPAG projetant sur le SLD. En parallèle, nous avons étudié le rôle du noyau réticulé paragigantocellulaire dorsal (DPGi) dans la genèse du SP. Bien que le DPGi fût déjà connu pour être responsable de l'inhibition du locus coeruleus (LC) durant les phases de SP, nous apportons ici un certain nombre d'arguments suggérant que le DPGi pourrait être responsable de l'inhibition, non seulement du LC, mais également de l'ensemble des neurones adrénergiques et noradrénergiques. Cela suggère donc que ce noyau joue également un rôle majeur dans la régulation du SP. Les données rapportées dans cette thèse permettent donc de mieux appréhender les mécanismes neuronaux contrôlant la survenue et la régulation du SP. En particulier, ils apportent de nouvelles données en faveur d'un rôle central de l'hypothalamus dans la régulation du SP puisqu'il constituerait le générateur principal de cet état.

L'anxiété est un symptôme prédominant au cours des périodes initiales de sevrage à la cocaïne et est considéré comme un facteur important de rechute. Le but de cette étude était de caractériser les dysfonctionnements cérébraux qui pourraient contribuer à l'expression de cet état pathologique chez le rat. Les rats sont traités avec de la cocaïne en chronique et le comportement anxieux est évalué au cours du sevrage dans différents paradigmes expérimentaux (tests du labyrinthe en croix surélevé, du confinement dans un bras ouvert surélevé et de l'enfouissement défensif). Nos résultats ont montré que le sevrage à la cocaïne induit un état anxieux élevé qui persiste pendant au moins 28 jours de sevrage. Nous avons ensuite utilisé l'immunohistochimie de Fos pour comparer les patterns d'activation cérébrale chez les rats sevrés et témoins après exposition au test de l'OA. Nos données ont montré que l'anxiété élevée des rats sevrés était accompagnée d'une altération de la réactivité des neurones glutamatergiques de la partie dorsale du cortex préfrontal médian (dCPFm) et de certaines régions sous-corticale (aires hypothalamiques latérale et antérieure et le noyau paraventriculaire du thalamus). Nous avons ensuite montré que l'inactivation pharmacologique du dCPFm avec du muscimol atténuait les comportements anxieux des rats sevrés suggérant ainsi une hyperréactivité de cette région corticale durant le traitement des informations de type anxieux. Notre étude amène des données nouvelles quant aux substrats neuronaux sous-tendant l'anxiété pathologique observée au cours du sevrage à la cocaïne et souligne l'importance du CPFm dans la régulation de cet état d'anxiété pathologique.

Studies have suggested the possibility that there is sensory (SS) afferent signaling from white adipose tissue (WAT) to the brain, which may play an important role in communication with the brain sympathetic nervous system (SNS) outflow to WAT. Therefore, we tested whether the SNS-SS feedback loop between the subcutaneous inguinal WAT (IWAT) and the epididymal WAT (EWAT) exists. These fat pads were chosen due to 1) their divergent role in manifestation of metabolic disorders with the IWAT being beneficial and the EWAT being detrimental, as well as 2) different lipolytic response to glucoprivic 2-deoxyglucose (2DG). By using retrograde tract tracers Fast Blue (FB) and Fluorogold (FG), we found that the IWAT is more innervated than EWAT by both the SS and SNS ganglia (T13-L3). Surprisingly, we found ~12-17% of double-labeled cells in the SNS and SS ganglia innervating fat depots, implying SNS-SS crosstalk loops between the IWAT and EWAT. Increased neuronal activation by 2DG was observed in the SNS ganglia to both IWAT and EWAT but not in the SS dorsal root ganglia. In addition, 2DG induced lipolysis in both fat pads with greater lipolytic properties in the IWAT as a result of higher density of the SNS-SS fibers. Collectively, our results show neuroanatomical reality of the IWAT and EWAT SNS-SS neural crosstalk with a coordinated control of lipolytic function.

Esta dissertação de mestrado tem por objetivo apresentar, analisar e discutir a experiência de ensino de Francês Língua Estrangeira para estudantes da Escola Politécnica da USP, por meio do Programa CFI (Curso de Francês para Iniciantes). Tal formação, iniciada em 2001, foi concebida pelo Centro de Línguas da Faculdade de Filosofia, Letras e Ciências Humanas da Universidade de São Paulo a pedido da Comissão de Relações Internacionais da Escola Politécnica, e tinha por finalidade preparar os alunos que fossem fazer dois anos de curso em faculdades de engenharia francesas (Ecoles Polytechniques, Ecoles Centrales, Ponts et Chaussés, etc), no âmbito do Programa Duplo Diploma em Engenharia promovida pela Poli-USP. Nosso estudo corresponde ao período em que se decidiu discutir a progressão e o equilíbrio entre as duas modalidades de ensino trabalhadas - o Francês, Língua Estrangeira (FLE) geral e o Francês com Objetivos Específicos (FOS) - na formação dos estudantes, que passara de 2 para 3 anos, incluindo um módulo específico (Módulo France) e cujo número de inscritos havia chegado a quinhentos por semestre letivo. Nesse período, coube à equipe pedagógica a concepção geral do curso e a preparação do material didático de cada um dos seis módulos de ensino oferecidos, o que trouxe resultados bastante positivos, como mostram os questionários respondidos por alunos do Duplo Diploma que participaram de tal formação. / The objective of this undergraduate thesis is to present, analyze and discuss the experience of teaching French as a foreign language for students at the Polytechnic School at University of São Paulo through the FCB Program (French Course for Beginners). This course, started in 2001, was designed by the Language Center at the College of Philosophy, Languages and Human Sciences of the University of São Paulo by request of the International Relations Commission of the Polytechnic School to prepare students who had been selected for the Dual Diploma Program in Engineering sponsored by Poli-USP, that is, a program in which students would spend two years of their undergraduate program at a French College of Engineering (Ecoles Polytechniques, Ecoles Centrales, Ponts et Chaussés, etc). Our study corresponds to the period in which we decided to reevaluate the progress and the balance between the two approaches used during the course general French as a Foreign Language (FFL) and French with Specific Objectives (FSO) a course which had increased from 2 to 3 years and which included a specific module (France module) and whose number of enrolled participants had reached 500 per semester. During this period, the pedagogical team (coordinators and teachers) were responsible for the general conception of the new course and for the textbooks of each one of the 6 teaching modules offered. The results obtained were extremely satisfactory as shown in the questionnaires answered by the Dual Diploma students who took this course.

O estudo do comportamento sexual em ratos machos envolve a análise da motivação e da performance sexuais. A distinção está entre procurar o contato sexual e estar apto para realizar o ato copulatório. Este comportamento é necessário para a preservação da espécie e não para sobrevivência do indivíduo, uma vez que abstinência sexual não tem, a curto prazo, consequências adversas para o organismo. Sendo assim, difere consideravelmente de outros comportamentos espontâneos como alimentação, hidratação, termorregulação ou respiração. Estudos mostram que o estresse com consequente ativação do eixo hipotálamo-hipófiseadrenal (HHA) e secreção de glicocorticóides pode alterar diversos parâmetros hormonais e comportamentais. O objetivo deste estudo foi analisar a motivação e performance sexuais de ratos machos e suas possíveis alterações diante da administração aguda e crônica de dexametasona (DEXA), um glicocorticóide sintético. Foram utilizados ratos da linhagem Wistar, mantidos em grupos com até 4 animais por caixa, em ciclo claro-escuro de 12hs a 21±1ºC. Para análises de performance sexual, ratos machos adultos sexualmente experientes, tratados com veículo ou com DEXA, aguda e cronicamente, foram expostos a fêmeas receptivas, filmando-se por 40 minutos. Os resultados das análises comportamentais e de imunoistoquímica para c-Fos mostraram que a administração aguda melhorou parâmetros do comportamento sexual e reduziu a expressão de neurônios marcados com c-Fos no BST, no MnPOd, no MnPOv, PVN e SON. Por outro lado, a administração crônica não alterou nenhum dos parâmetros do comportamento e aumentou o número de células positivas para c-Fos no SON. Para avaliação da motivação sexual, ratos machos, sexualmente inexperientes, tratados com veículo ou DEXA, foram colocados em um aparato onde havia uma fêmea receptiva (incentivo sexual) e um macho sexualmente experiente (incentivo social), filmandose por 20 minutos, tratados com veículo ou tratados com DEXA. Os resultados mostraram que a administração aguda de dexametasona aumentou a motivação sexual, enquanto a administração crônica não modificou este comportamento. Em conjunto, estes resultados sugerem que a administração aguda de dexametasona aumentou a motivação sexual em ratos machos sexualmente inexperientes através de mecanismos envolvidos com a supressão do eixo HHA. Além disso, administração aguda de DEXA melhorou parâmetros da performance sexual às custas de diminuição da atividade neuronal em áreas hipotalâmicas relacionadas ao controle neuroendócrino em ratos machos sexualmente experientes. / The study of sexual behavior in male rats involves the analysis of motivation and sexual performance. The distinction between them is seeking sexual contact and be able to perform the copulatory act. This behavior is required for preservation of the species and not to survival of the individual, as abstinence has not, the short-term adverse effects for the organism. Thus, it differs considerably from other spontaneous behaviors such as feeding, hydration, thermoregulation or respiration. Studies show that stress and consequent activation of the hypothalamic-pituitaryadrenal (HPA) and secretion of glucocorticoids can alter various hormonal and behavioral parameters. The aim of this study was to analyze the motivation and sexual performance of male rats and its possible changes in the face of acute and chronic administration of dexamethasone (DEXA), a synthetic glucocorticoid. We used Wistar rats, kept in groups with up to four animals per cage in light-dark cycle of 12h at 21 ± 1 ° C. For analyzes of sexual performance, sexually experienced adult male rats treated with vehicle or DEXA, acute and chronic, were exposed to receptive females, recording 40 minutes. The results of behavioral analysis and immunohistochemistry for c-Fos showed that acute administration improved parameters of sexual behavior and decreased the c-Fos neurons in BST, the MnPO d in MnPOv, PVN and SON. Moreover, the chronic administration did not affect any of the parameters of performance and increased the number of positive cells in the SON c-Fos. For assessment of sexual motivation, male rats, sexually inexperienced, treated with vehicle or DEXA, were placed in an apparatus where there was a receptive female (sexual incentives) and a sexually experienced male (social incentive), recording 20 minutes, treated treated with vehicle or DEXA. The results showed that the acute administration of dexamethasone increased sexual motivation, while the chronic administration did not modify this behavior. Together, these results suggest that acute administration of dexamethasone increased sexual motivation in male rats by inexperienced sexually mechanisms involved in suppression of the HPA axis. Furthermore, acute administration of DEXA improved sexual performance parameters by decreased neuronal activity in hypothalamic areas related to the neuroendocrine control of sexually experienced male rats. / Fundação de Amparo à Pesquisa do Estado de Minas Gerais - FAPEMIG