O comportamento gregário é comum em algumas espécies de Opiliones. No período noturno indivíduos gregários saem do abrigo para forragear e ao amanhecer retornam ao ambiente de repouso. Químicos de coespecíficos têm sido discutidos como mediadores do retorno ao abrigo nos indivíduos da subordem Eupnoi, mas até o momento nada se sabe sobre as pistas que os indivíduos da subordem Laniatores utilizam para retornar ao abrigo. Recentemente, uma grande diversidade de receptores olfativos foi descrita nessa subordem e o uso do olfato à curta distância (< 2 cm) já foi documentado em agregados. Testamos as hipóteses do uso do olfato à longa distância (50 cm) na atração por (1) químicos voláteis emitidos diretamente de coespecíficos e (2) químicos voláteis próprios e de coespecíficos deixados previamente nos abrigos. Utilizamos um olfatômetro em formato de Y. Usamos como estímulos fêmeas e machos coespecíficos para (1) e abrigos dos sujeitos experimentais, de coespecífico do mesmo sexo e controle para (2). Para (1) machos de M. cuspidatus escolheram significativamente o lado do olfatômetro com machos coespecíficos. Fêmeas de M. cuspidatus não mostraram preferência por nenhum dos estímulos. Para (2) machos e fêmeas de M. cuspidatus não escolheram significativamente nenhum estímulo do olfatômetro. Esses resultados nos mostram que talvez machos de M. cuspidatus tenham maior sensibilidade olfativa comparada ao das fêmeas coespecíficas. Os machos de M. cuspidatus não mostraram preferência por fêmeas coespecíficas talvez porque no momento do experimento as fêmeas não estivessem liberando voláteis. Nossos resultados também mostram que indivíduos de M. cuspidatus não são atraídos à distância por químicos deixados no abrigo, talvez porque esses químicos sejam pouco voláteis ou porque os indivíduos detectaram o odor, mas optaram por não escolher o braço com odor próprio e nem de coespecífico. O olfato parece ser mais importante do que anteriormente mencionado em Opiliones / Gregarious behavior is common in some species of Opiliones. At night, gregarious individuals leave their shelter to forage and at dawn return to the original spot. Chemicals of conspecifics have been suggested to be mediators of homing in individuals of the suborder Eupnoi, but so far nothing is known about the cues used in the suborder Laniatores. Recently, a large diversity of olfactory receptors has been described in this suborder and the use of olfaction at close range (<2 cm) has already been documented in aggregations. We tested the hypotheses of the use of olfaction at long range (50 cm) in the attraction by (1) volatile chemicals emitted directly from conspecifics and (2) volatiles (own chemicals and conspecific chemicals) previously left in shelters. We used a Y-shaped olfactometer. We used conspecific females and males as stimuli for (1) and shelters of the experimental subjects and of conspecifics of the same sex for (2). For (1) males of M. cuspidatus chose significantly the side of the olfactometer with conspecifics males. Females did not choose any stimuli. For (2) males and females of M. cuspidatus did not choose any of the stimuli. Males may therefore be more sensitive than females. Males of M. cuspidatus did not show preference for conspecific females, perhaps because at the time of the experiment females were not releasing volatiles. Individuals of M. cuspidatus are not attracted at a distance by chemicals left in the shelter, perhaps because these chemicals are not volatile or because the individuals detected the odor, but chose not to walk towards it. Olfaction seems to be more important than previously mentioned in Opiliones

A área tegmental ventral (VTA) contém neurônios dopaminérgicos do grupamento A10 e envia projeções muito densas para o estriado ventral. Esta circuitaria está crucialmente envolvida em mecanismos de recompensa. Recentemente, a organização destas projeções foi reexaminada por Ikemoto S. (Brain Res. Rev., 56:27-78, 2007), em um estudo de rastreamento retrógrado minucioso, sendo proposto a subdivisão destas projeções em um sistema dopaminérgico mesoestriatal ventromedial que inerva a concha medial do accumbens e o tubérculo olfatório medial, e um sistema dopaminérgico mesoestriatal ventrolateral que inerva o cerne e a concha lateral do accumbens e o tubéculo olfatório lateral. Afim de complementar o conhecimento destas projeções, no presente estudo elas foram examinadas com a técnica anterógrada da leucoaglutinina do Phaseolus vulgaris. Nossos resultados indicam que há um extenso embricamento dos campos terminais estriatais inervados por diferentes setores/núcleos da VTA e reforçam a noção de que as eferências da VTA podem ser subdivididas em um sistema mesoestriatal ventromedial e um sistema mesoestriatal ventrolateral. Eles revelam ainda que as projeções da VTA para o estriado ventral têm uma organização topográfica médio-lateral mais complexa do que previamente reconhecido, a faixa médio-lateral do estriado ventral inervada depende de uma combinação da região médio-lateral e dorsoventral da VTA. Assim, as regiões mais ventrais e mediais da VTA (correspondendo ao núcleo interfascicular) inervam os distritos mais mediais do estriado ventral (a concha dorsomedial do accumbens e a extremidade medial do tubérculo olfatório), e as regiões mais dorsais e laterais da VTA (correspondendo à região dorsolateral do núcleo parabraquial pigmentoso) se projetam para os distritos mais laterais do estriado ventral (o cerne lateral e a concha lateral do accumbens, o caudado-putâmen ventral e o tubérculo olfatório lateral). Por outro lado, as projeções da VTA para o estriado ventral não possuem uma organização topográfica rostrocaudal. Outro fato a ser destacado é que a organização das projeções mesoestriatais da VTA lembra o padrão das projeções córticoestriatais, sendo observado no estriado, além de um campo terminal principal, pequenos focos isolados de marcação. / The ventral tegmental area (VTA) contains dopaminergic neurons of the A10 group and sends dense projections to the ventral striatum. This circuitry is critically involved in reward mechanisms. Recently, the organization of these projections was reexamined by Ikemoto S. (Brain Res. Rev., 56:27-78, 2007) in a detailed retrograde tracing study, being proposed that these projections can be subdivided into two main systems, a ventromedial mesostriatal dopaminergic system that innervates the medial shell of the accumbens and medial olfactory tubercle, and a ventrolateral mesostriatal dopaminergic system that targets the core and lateral shell of the accumbens and lateral olfactory tubercle. In order to complement these data, in the present study the VTA mesostriatal projections were examined with a sensitive anterograde tracing technique using the Phaseolus vulgaris leucoaglutinin. Our results indicate that there is an extensive overlap of terminal fields innervated by different sectors / nuclei of the VTA and reinforce the notion that VTA efferents can be subdivided into a ventromedial and a ventrolateral mesostriatal system. They also show that the VTA projections to the ventral striatum have a mediolateral topographical organization more complex than previously acknowledged. In fact, projections along the mediolateral dimension of the ventral striatum depends on a combination of the mediolateral and dorsoventral axis of the VTA. In other words, the most ventral and medial parts of the VTA (corresponding to the interfascicular nucleus) innervates the most medial districts of the ventral striatum (corresponding to the dorsomedial shell of the accumbens and medial tip of the olfactory tubercle), and the most dorsal and lateral parts of the VTA (corresponding to the dorsolateral region of the parabrachial pigmented nucleus) project to the most lateral districts of the ventral striatum (lateral core and lateral shell of the accumbens, ventral caudate-putamen and lateral olfactory tubercle). Moreover, VTA projections to the ventral striatum do not seem to have a rostrocaudal topographical organization. It is also of note that the organization of the VTA mesostriatal projections shares features with cortico-striatal projections, in the sense that both fiber systems have a main terminal field and also give rise to small, scattered isolated foci of terminal labeling.

A área de transição amígdalo-piriforme (APir) está situada na confluência dos córtices piriforme, periamigdalóide e entorrinal lateral (ENTl). Com técnicas de rastreamento retrógrado foi observado que as principais aferências da APir se originam do bulbo olfativo, dos córtices piriforme, insular disgranular e agranular posterior, perirrinal, da formação hipocampal e da amígdala. Outras estruturas como o núcleo da banda diagonal de Broca, o pálido ventral, a substância inominada sublenticular, o tálamo da linha média, o núcleo dorsal da rafe, o locus coeruleus e a área parabraquial são fontes de aferências mais modestas a esta área de transição. A APir e o ENTl diferem no que diz respeito à origem de suas aferências mesocorticais, amigdalianas e talâmicas. Assim, a APir está em condições de integrar informações olfativas, gustativas, interoceptivas gerais e polissensoriais complexas e, através de suas projeções para a amígdala expandida, striatum ventral e formação hipocampal, influenciar a expressão de comportamentos motivados. / The amygdalo-piriform transition area (APir) lies at the junction of the piriform, periamygdaloid and entorhinal cortices. The afferent connections of this olfactory district were studied with retrograde tracing methods using the cholera toxin B subunit and Fluoro-Gold as tracers. Our retrograde experiments showed that the main input sources to APir derive from the olfactory bulb, mesocortical and allocortical areas including the dysgranular insular, posterior part of the agranular insular, piriform, lateral entorhinal and perirhinal cortices, temporal field CA1 of Ammon horn, ventral subiculum, as well as the endopiriform nucleus and the amygdaloid complex (anterior basomedial, posterior basolateral and anterior, posterolateral, posteromedial cortical nuclei). Several other structures among which the diagonal band, ventral pallidum, sublenticular substantia inominatta, midline thalamic nuclei, dorsal raphe nucleus, locus coeruleus and parabrachial area provide more modest inputs to APir. Our results suggest in addition that projections from mesocortical areas, hippocampal formation and the posterior basolateral amygdaloid nucleus to APir are topographically organized. Fluoro-Gold injections in the ventrolateral entorhinal cortex indicate that the afferent connections of this district differ in many regards from the afferent connections of APir. Cortical and amygdaloid inputs suggest tha APir is chiefly involved in the processing of olfactory, gustatory, visceral and somesthesic information, whereas the ventrolateral entorhinal cortex seems to be more crucially related with visual and auditory processes. APir is also less densely projected upon by midline thalamic nuclei than the lateral entorhinal cortex. Taken as a whole our results suggest that APir is in position to relay highly integrated olfactory, gustatory, interoceptive and somesthesic information to the extended amygdala, ventral striatum and ventral subiculum, and as such modulate the expression of motivated and emotional behavior.

INTRODUÇÃO: Dor facial crônica abrange várias condições que podem se apresentar isoladas ou concomitantes, cujas evidências têm apontado para o impacto local e na saúde como um todo. Morbidades odontológicas e sistêmicas podem estar presentes nesses indivíduos e afetar a sensibilidade álgica. Assim, o objetivo deste estudo foi investigar doentes com dor facial crônica quanto à prevalência e perfil de morbidades odontológicas e sistêmicas, em comparação com indivíduos sem dor facial. MÉTODOS: Cento e sessenta e quatro pacientes do ambulatório de Dor Neuropática Orofacial do Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo, com idade média de 57,7±15,75 anos, e 133 indivíduos-controles sem queixas de dor, com idade média de 49,83±22,55 anos, foram selecionados. Foram avaliadas as características clínicas e funcionais orofaciais e o histórico médico prévio, sendo utilizado um protocolo de avaliação sensitiva superficial que incluiu as seguintes modalidades: percepção mecânica (táctil e vibratória), percepção térmica (frio e calor), percepção álgica (superficial e profunda), percepção à estimulação elétrica, sensibilidade gustativa (doce, azedo, amargo e salgado) e limiar olfativo. Para a tabulação, os doentes foram divididos em dois subgrupos (dor facial neuropática e dor facial complexa). Os dados foram analisados estatisticamente considerando-se um nível de significância de 5%. RESULTADOS: Houve maior prevalência de doenças gastrointestinais, respiratórias e psiquiátricas no grupo de dor facial complexa quando comparado aos outros dois grupos estudados (dor facial neuropática e controle) (p < 0,033, p < 0,014 e p < 0,001, respectivamente). A prevalência de ausências dentárias foi maior nos indivíduos com dor neuropática (49,2%) quando comparados ao grupo de dor complexa (37,9%) e aos controles (30,1%). Estes últimos apresentaram mais cáries do que os doentes com dor, enquanto que alterações mandibulares foram mais comuns nos grupos de doentes (p < 0,050). Os doentes com dor neuropática apresentaram mais bruxismo (p=0,005), e os diversos tratamentos odontológicos, fisioterápicos e cirúrgicos se associaram a alterações nos limiares sensitivos. Quanto às morbidades sistêmicas, houve maior prevalência de doenças cardiovasculares na maioria dos grupos de doentes, sendo que tanto estas quanto os fármacos utilizados para seu tratamento também estavam relacionados principalmente a anormalidades sensitivas somestésicas e olfativas. CONCLUSÕES: A maior prevalência de morbidades em doentes com dor facial complexa parece relacionar-se com um caráter sindrômico e funcional dessas condições, sendo que a presença de morbidades se associou com a dor e com alterações sensitivas. O grupo de dor facial neuropática apresentou maior comprometimento funcional mandibular e perdas dentárias, sendo que estas se associaram a morbidades sistêmicas / INTRODUCTION: Chronic facial pain is a term that includes several conditions that might be present isolated or concomitant. The evidences have suggested an impact in general health and dental or systemic comorbidities can be found in these patients affecting their sensory pain perception. Thus, the objective of this study was to investigate patients with chronic facial pain about the prevalence and profile of general and local oral conditions in comparison to subjects with no facial pain complaint. METHODS: Hundred-sixty-four patients from the Neuropathic Facial Pain Clinic of Hospital das Clínicas of the Medical School of the University of São Paulo, with mean age of 57.7±15.75 years old, and 133 control subjects with no pain complaints, with mean age of 49.83±22.55 years old, were selected. The evaluation protocol included: clinical and functional orofacial characteristics, previous medical history and sensory evaluation of the following modalities: mechanical (tactile and vibratory), thermal (cold and warm), pain (superficial and deep), electric stimulation, gustative (sweet, sour, bitter and salty) and olfactory thresholds. The patients were divided into two subgroups (neuropathic facial pain and complex facial pain). Data were statistically analyzed considering a significance level of 5%. RESULTS: The prevalence of gastrointestinal, respiratory and psychiatric diseases was higher in the group of patients with complex facial pain compared to the other groups (p < 0.033, p < 0.014 e p < 0.001, respectively). The frequency of dental absences was higher in patients with neuropathic pain (49,2%) when compared to complex facial pain (37,9%) and controls (30,1%). The controls had more decays that the patients, while mandibular masticatory abnormalities were more frequent among the patients (p < 0.50). Neuropathic facial patients had more bruxism (p=0.005) and the common dental, physiotherapic and surgical treatments were associated with abnormalities in sensory thresholds. Cardiovascular disease was the most common morbidity, and systemic conditions as well as the medication to treat them were associated with abnormalities in somatosensory and olfactory thresholds, mainly. CONCLUSIONS: The high prevalence of morbidities in patients with complex facial pain seems to be associated with a syndromic and functional aspect of these conditions; the frequency of systemic morbidities and pain were associated with sensory abnormalities. Patients with neuropathic facial pain had more mandibular function complications and teeth losses, which were associated with systemic morbidities

Quoique très immature à la naissance, l’opossum grimpe de l’orifice urogénital de la mère jusqu’à une tétine à laquelle il s’accroche pour poursuivre sa maturation. Des informations sensorielles sont nécessaires pour que l’animal atteigne la tétine et que le réflexe d’attachement soit déclenché. Une modalité sensorielle envisagée est l’olfaction. Or, des expériences physiologiques effectuées au laboratoire sur des préparations in vitro suggèrent que le système olfactif central est trop immature pour influencer les comportements moteurs. Une étude immunohistochimique employant un marqueur de maturité axonique (NF200) a montré une absence de marquage dans le cerveau antérieur, à l’exception d’un mince faisceau reliant les bulbes olfactifs aux régions caudales du cerveau. L’implication de l’olfaction dans les comportements du nouveau-né est donc peu probable, mais la présence de ce faisceau est intrigante et l’étude de son développement est approfondie dans le présent travail. Le développement du faisceau exprimant NF200 est décrit de la naissance jusqu’à la fin de la 2e semaine postnatale, âge auquel le marquage NF200 n’est plus observé à ce niveau. Il est aussi montré que le trajet de ce faisceau se superpose à celui de fibres nerveuses exprimant GnRH1, une neurohormone exprimée par des neurones hypothalamiques chez l’adulte. Les résultats indiquent que ce faisceau est le nerf terminal et pourrait servir de voie pionnière pour la croissance des fibres GnRH1. Aucun marquage NF200 dans le cortex olfactif n’est observé avant P15, supportant l’idée que le système olfactif n’influence pas les comportements de l’opossum nouveau-né. / While quite immature at birth, the opossum is nevertheless able to crawl from the urogenital opening to a mother's nipple to which it attaches to pursue its development. Sensory information are required to guide the newborn to the nipple and induce attachment. Olfaction is one of the sensory modalities often proposed. However, recent physiological experiments in the laboratory using in vitro preparations suggest that the olfactory system is too immature to influence the newborn behaviors. Furthermore, an immunohistochemical study using a marker of axonal maturity (neurofilament 200kDa, NF200) has shown that the prosencephalon is nearly devoid of mature fibers except for a thin fascicle running from the olfactory bulbs to more caudal areas of the brain. Olfaction is thus unlikely to guide the locomotion of the newborn, but the presence of this fascicle is intriguing and its development is studied in the present thesis. This fascicle is described from the day of birth to the end of the second postnatal week, when NF200 labeling is no more visible in this region. It is also shown that this fascicle superpose with fibers expressing GnRH1, a neurohormone characterizing hypothalamic neurons in the adult. The results indicate that this fascicle is the terminal nerve, and might serve as a pioneer pathway to GnRH1 fibers cells. Until P15, the olfactory cortex was devoid of NF200 projections, supporting that the olfactory systems is too immature to influence the behavior of newborn opossums.

The zebrafish (Danio rerio) promises to meet the growing needs of gerontological and neurobehavioral research by possessing highly conserved anatomy and physiology with all other vertebrates, while having low maintenance costs and requiring only simple care. The neurological and physiological bases of learning, memory formation, and memory retention have been studied in a variety of model organisms, such as the rat, mouse, sheep, and several teleost fishes, the notable example being the zebrafish. Unfortunately, most of these animals are poorly suited to senescence research due to costs, care requirements, or long life spans. My research expands upon our rapidly growing understanding of zebrafish neurobiology, learning processes, sensory modalities, and memory retention. Two pairs of distinct aversive conditioning experiments using classic shuttlebox designs compared the effects of sensory modality and conditioned-unconditioned stimulus (CS-US) intervals, the time delay between application of conditioned sensory stimulus and delivery of the stressful unconditioned stimulus in the event of failure to avoid it, upon memory formation and retention. These studies yielded a general spectrum of results against which future conditioning studies may be compared. Both visual and olfactory stimuli were tested, as were 10 second and 15 second CS-US intervals. Successes were scored when the fish crossed the shuttlebox hurtle within the CS-US interval, thereby avoiding the negative unconditioned stimulus. After a three-month delay, ten additional trials were conducted to compare the long-term memory retention resulting from each protocol. When testing a 15s CS-US interval, olfactory conditioning was significantly more likely (39%) to produce a successful outcome (memory formation) than visual conditioning. Grouped results reveal that the second pair of experiments, each with a 10s CS-US interval, yielded significantly more successful memory formation than a 15s CS-US interval. A significant difference was found when comparing the results of any two experiments, except between the results of the visual and olfactory 10s interval experiments). Only the olfactory experiment using a 15s CS-US interval yielded memory retention results significantly higher than the mean of memory retention results from the four experiments. These findings offer inconclusive evidence supporting olfaction’s strong role in memory formation and retention in zebrafish. The results expand our understanding of the relationship between the olfactory and visual senses and memory in the zebrafish and indicate the olfactory sense’s key role in vertebrate neurobiology, warranting further research into the effects of aging on the olfactory-memory modality.

Abstract This thesis is a study of the odour responses of insect olfactory (or odorant) receptor neurons (ORN) of blowfly (Calliphora vicina), mosquito (Aedes communis), fruitflies (Drosophila melanogaster and D. virilis) and large pine weevil (Hylobius abietis). A power-law dependence (similar to Stevens' law in psychophysics) was obtained for the action potential rate of ORN responses vs. odour concentration in measurements with metal microelectrodes from blowfly ORNs and an analysis system was developed for the extracellularily recorded action potentials (or nerve pulses). Odour exposure sequences were used to study action potential rates quantitatively as a function of odour concentration in air exposure. For an odour exposure sequence, a known initial amount of the odour compound in a filter paper inside a Pasteur pipette at the beginning of repeated exposures caused a gradual dilution of the odour concentration in the exposure sequence. The concentration at each exposure was calculated according to the discrete multiple headspace extraction and dilution (DMHED) method. The estimated odour concentration was assumed to obey in the method an exponential law with respect to the exposure number in the sequence. Despite that many uncontrollable parameters remain for measuring quantitatively the characteristics of the ORNs, the results obtained, e.g., sensitivity, specificity, adaptability, and the power-law realation are both biologically and technically very interesting. A time-to-voltage converter (TVC) was utilized for the response analysis in determining action potential intervals originating from a single ORN. A precision analysis of TVC was also performed. With the mosquito (Aedes communis), fruitflies (Drosophila melanogaster and D. virilis) and large pine weevil (Hylobius abietis) antennae were tested for inhibitory and excitatory effects to find out repellents and attractants. Human sweat was found to cause strong stimulus exposure in the responses of the mosquito ORNs and Neutroil® caused inhibitory responses in pine weevil ORNs, respectively. The power-law exponents for blowfly ORNs were about 0.19 in the case of 1-hexanol (HX), 0.065 in the case of 1,4-diaminobutane (14DAB) and 0.32 in the case of butyric acid (BA). The corresponding Stevens' law exponent values 0.39 and 0.33 have been reported for HX and BA, respectively, by Patte et al. (1975).

La cellule microgliale, seule cellule du système immunitaire résidant en permanence dansle système nerveux central, a un rôle important dans le développement cérébral. Elle participe à l’élagage des neurones en développement, via le marquage des épines dendritiques à éliminer par les facteurs du complément. Certaines régions cérébrales continuent à produire des neurones à l’âge adulte. Chez le rongeur, des néo-neurones sont ainsi générés dans la zone sous-ventriculaire tout au long de la vie et migrent vers le bulbe olfactif où ils s’intègrent au réseau pré-existant. Le but de ce travail est de caractériser l’implication de la microglie dans le développement et l’élagage des neurones nés dans le système olfactif de la souris à l’âge adulte. Pour ce faire, nous avons combiné des méthodes d’étude du comportement, d’immunohistochimie, de microscopie confocale et d’analyse d’images pour explorer les interactions entre microglie et neurones bulbaires dans un contexte normal ou pathologique : déafférentation olfactive, inflammation par les lipopolysaccharides (LPS) bactériens, dérégulation de l’axe hypothalamus-pituitaire-adrénal ou déficience génétique en complément C3 (C3−/−). Nous avons découvert que la microglie phagocyte préférentiellement les néo-neurones nés à l’âge adulte par rapport aux neurones néonataux, et que cette tendance s’accentue encore en cas de déafférentation sensorielle. Ainsi, la microglie façonne le réseau neuronal du bulbe en fonction des expériences sensorielles. La densité d’épines dendritiques est peu impactée par l’activation microgliale, et n’est pas modifiée par l’absence de complément C3. Cela suggère que l’élagage des néo-neurones du bulbe olfactif pourrait ne pas mettre en jeu la microglie et le complément C3. En conclusion, ce travail de thèse montre l’importance de la microglie dans la régulation du taux de neurogenèse bulbaire en fonction de l’activité sensorielle. L’implication de la microglie dans les mécanismes de plasticité neuronale ouvre des perspectives de recherche pour des thérapies ciblées sur les cellules microgliales. / Microglia are resident immune cells in the central nervous system. They participate in the pruning of developing neurons. Complement factors are key markers of the dendritic spines to eliminate...

Comment les différentes formes de mémoire sont-elles encodées et comment interagissent-elles ? L'identification des réseaux neuronaux sous-jacents aux différentes formes de mémoire est une approche performante qui permet de mieux comprendre la dynamique des phases de mémoire et leurs interactions. La Drosophile représente un modèle de choix pour l'étude des mécanismes d'apprentissage et de mémorisation. Son cerveau est composé de 100.000 neurones et des outils génétiques permettent d'étudier fonctionnellement les circuits neuronaux avec une résolution proche du neurone unique. On utilise deux sortes d’apprentissage olfactif associatif : l’un, appétitif, repose sur l’association entre une odeur etdu sucre, et l’autre, aversif, associe une odeur et des chocs électriques. On distingue deux types de mémoires appétitives, une à court-terme et une à long-terme. Notre équipe a montré récemment que ces mémoires appétitives se forment indépendamment. La mémoire aversive a été décomposée en deux mémoires labiles à court-terme et à moyen terme, et deux mémoires consolidées : la mémoire à long terme (LTM) qui repose sur une synthèse protéique de novo et la mémoire résistante à l’anesthésie (ARM). Les corps pédonculés (CP), le centre de l'apprentissage et de la mémoire olfactive de la Drosophile, forment une structure bilatérale d’environ 2.000 neurones par hémisphère cérébral, appelés cellules de Kenyon. Celles-ci ont été classées en trois sous-types–γ, αβ et α’β’–en fonction des ramifications de leurs projections axonales qui définissent trois lobes médians (β, β’, γ) et deux verticaux (α, α’). Certains réseaux neuronaux responsables du rappel de la mémoire ont été caractérisés mais la correspondance entre ces réseaux et les phases de mémoire n’est encore que parcellaire. Grâce à des outils thermogénétiques nous pouvons inhiber une population neuronale restreinte pendant la phase de rappel spécifiquement. Au cours de ma thèse j'ai affiné la dissection des différentes phases de mémoire olfactive tant au niveau comportemental qu'au niveau des réseaux neuronaux. Nous avons pu attribuer à chaque phase de mémoire un réseau neuronal précis allant des neurones intrinsèques des CP aux neurones efférents impliqués dans le rappel de la mémoire. Nous avons ainsi mis en évidence une distribution spatio-temporelle de six phases de mémoires aversives mettant en jeu des réseaux neuronaux distincts et complémentaires. Nous avons montré que la ARM, jusqu’ici considérée comme une phase de mémoire unique est en réalité une mémoire composite. Nous avons identifié et localisé trois formes de ARM : la ARM immédiate, la ARM à moyen terme et la ARM à long-terme localisées respectivement dans les neurones αβ, γ et α’β’. Les deux formes séquentielles de mémoire labile immédiate et à moyen-terme ont été localisées dans les neurones γ et αβ respectivement. Nous avons aussi identifié les neurones extrinsèques de rappel de ces différentes formes de mémoire. Nous avons montré que les neurones MB-V2, précédemment décrits par notre équipe, assurent le rappel des mémoires localisées dans les neurones αβ et α’β’. Nous avons également identifié un nouveau type de neurones impliqués dans le rappel mnésique, les neurones MB-M6, efférents aux lobes γ et β’. Il existe un neurone MB-M6 par hémisphère. Ceux-ci sont impliqués dans le rappel des phases de mémoire aversive impliquant les neurones γ et α’β’. Nous avons aussi montré que les neurones MB-M6 sous tendent le rappel de la mémoire appétitive à court-terme. Ces découvertes permettent de dresser un tableau complet des circuits de sortie des corps pédonculés sous-tendant chaque phase de mémoire. Ce schéma global laisse apparaître qu’à un temps donné, deux formes de mémoire distinctes ne partagent jamais le même circuit. Nos travaux ouvrent la voie à l’étude comparée des modifications physiologiques encodant les différentes formes de mémoire associative chez la Drosophile. / A fly can form robust aversive associative olfactory memory after pairing an odor with electric shocks. Appetitive memory forms in a starved fly after pairing an odor with sugar delivery. Both types of olfactory memory rely on the mushroom bodies (MBs), a paired lobed structure of ∼2,000 neurons—the Kenyon cells (KCs)—per brain hemisphere. Based on their axonal morphology, KCs are classed into three different subtypes: axons from α/β and α′/β′ KCs branch into vertical (α and α′) and medial (β and β′) lobes, whereas axons from γ neurons form only a medial γ lobe. Drosophila can form two types of consolidated memories: LTM, which relies on de novo protein synthesis, and ARM, which does not. Droophila can also sequetially forms an immediate labile memory and a middle term labile memory.We have demonstrated a spatio-temporal distribution of six phases of aversive memories involving distinct and complementary neural networks. We have identified and located three forms of ARM: immediate ARM, middle term ARM and long-term ARM located respectively in αβ neurons, γ and α'β’. Both sequential forms of immediate labile memory and middle term memory were localized in γ and αβ neurons respectively. We also identified the extrinsic neurons required for the retrieval of these different forms of memory. We showed that MB-V2 neurons, previously described by our team, ensure the recall of memories localized in αβ and α'β’ neurons. We identified a specific pair of MB-efferent neurons, named M6 neurons. These are involved in the retrieval of aversive memories involving γ and α'β ‘ neurons. We have also shown that MB-M6 neurons are required for the retrieval of appetitive short-term memory.

Ce projet de recherche est focalisé sur le lien entre la structure des molécules odorantes et leurs interactions avec les récepteurs olfactifs exprimés dans les neurones olfactifs. Cette recherche fondamentale est d'une importance primordiale pour la construction d'un «nez virtuel », physiologiquement inspiré, qui reproduit la fonction des 400 types de récepteurs olfactifs impliqués dans la détection des odeurs. Ici, chaque récepteur olfactif est représenté par un système moléculaire qui est reproduit atome par atome dans un modèle informatique. Un protocole optimal a été conçu pour prédire les structures de ces récepteurs grâce à l’analyse bioinformatiques de leurs séquences sous contraintes de données expérimentales. Ensuite, les bases de la relation entre la séquence d’un récepteur et son mécanisme d’activation en fonction de la structure d’une molécule odorante liée à sa cavité ont été établies. Par ailleurs, l’analyse des structures de molécules d’une même famille olfactive peut conduire à l’identification des récepteurs impliqués dans leur perception. L’ensemble de ces résultats constitue les bases pour l’étude des relations structure-odeur à l’ère post-génomique. / This research project is focused on the link between chemical structures of odorant molecules and their interactions with odorant receptors expressed in olfactory neurons. This basic research is of primary importance for building a physiologically-inspired “computational nose” that reproduces the function of the 400 types of odorant receptors involved in the perception of smells. Here, each odorant receptor is represented as a molecular system, reproduced atom per atom in a computational model. An optimal protocol has been built to predict the structure of these receptors using bioinformatics analyses of their sequences under the constraints of experimental data. Then, the relationship between the sequence and the activation mechanism of a receptor as a function of the structure of a molecule bound to its cavity has been established. Furthermore, the structural analysis of molecules belonging to the same olfactory family was shown to lead to the prediction of some receptors involved in their perception. These results constitute a basis for structure-odor relationships studies in the postgenomic era.