No description available.

Este trabalho descreve uma simulação computacional biologicamente plausível do sistema olfativo de vertebrados. O modelo construído foi capaz de reproduzir satisfatoriamente características importantes observadas no sistema olfativo de vertebrados, incluindo a recepção de diferentes concentrações e tipos de odores no epitélio olfativo e a propagação dessa informação para o bulbo. Ele também tornou possível a observação de diferentes padrões de resposta odorífera, tanto no epitélio como no bulbo, associados a diferentes odores usados nas simulações. / This work describes a biologically plausible simulation of the olfactory system of vertebrates. The constructed model was capable of reproducing satisfactorily important characterisitics observed in the vertebrate olfactory system, including the reception of different concentrations and odor types at the epithelium and the propagation of this information to the olfactory bulb. Also, it made possible the observation of the different response patterns, both in the epithelium as in the olfactory bulb, associated with different odors used in the simulations.

Esse trabalho consiste no estudo de alguns mecanismos responsáveis pela geração das oscilações elétricas observadas no sistema olfativo de vertebrados e das possíveis funções que essas oscilações possam ter no processamento da informação olfativa. Da-se especial atenção ao papel desempenhado pelo ritmo respiratório e pelas sinapses químicas e elétricas nesse processo. Para realizar essa investigação, foram utilizados modelos computacionais que reproduzem aspectos da anatomia e da fisiologia do epitélio olfativo, do bulbo olfativo e do córtex piriforme. Os modelos foram desenvolvidos e simulados no neurossimulador GENESIS, funcionando no sistema operacional LINUX. A análise dos resultados foi feita no programa MATLAB (Mathworks™). Inicialmente, a tese faz uma descrição do substrato neurobiológico que compõe as camadas iniciais do sistema olfativo, incluindo o epitélio, bulbo e córtex olfativo, e de como a informação olfativa é processada por cada camada, discutindo a importância do sentido olfativo e a relevância da neurociência computacional no estudo da origem e do papel das oscilações elétricas existentes nesse sistema (Capítulo 1). O capítulo 2 descreve os materiais e métodos utilizados para a construção dos modelos computacionais e para análise dos resultados. O capítulo 3 faz uma descrição detalhada do modelo computacional utilizado e dos experimentos realizados com o modelo. Finalmente, o capítulo 4 apresenta e discute os resultados das simulações realizadas e o capítulo 5 estende essa discussão, concluindo a tese. O capítulo 6 contém as referências bibliográficas utilizadas no trabalho. Os resultados do trabalho sugerem que as oscilações elétricas no sistema olfativo poderiam ser geradas em várias estruturas e níveis de organização, abrangendo os níveis moleculares, celulares e de sistemas neurais. E que as sinapses químicas e elétricas, assim como os ritmos respiratórios, podem ter um papel fundamental na geração dessas oscilações. Assim, o modelo construído propõe uma explicação plausível para a origem das oscilações elétricas no sistema olfativo de vertebrados e discute as possíveis funções que essas oscilações teriam no contexto do processamento da informação sensorial. / This work is a study of some mechanisms associated with the generation of electric oscillations in the vertebrate olfactory system. Special attention is given for the role of the respiratory rhythm, chemical synapses and electrical synapses in this process. The possible functions of the electric oscillations in olfactory information processing are explored. A computational model that reproduces aspects of the anatomy and physiology of the olfactory epithelium, bulb and piriform cortex was utilized to realize this investigation. The models were developed and simulated in the GENESIS neurosimulator, running under the LINUX operational system. The analysis of the results was made in the software MATLAB (Mathworks™). In the beginning, the thesis describe the neurobiological substracts of the initial layers of the olfactory system, including the olfactory epithelium, bulb and piriform cortex, and explore how the olfactory information is processed by each layer. The chapter 1 presents the importance of the olfactory sense and the use of computational neuroscience to study the role of the electric oscillations in this system. The chapter 2 explains the material and methods utilized to develop the computational model and to analyse the data generated by the model. The chapter 3 describes the used computational model and the experiments realized with the model. Finally, the chapter 4 presents and discusses the results of the simulations. The chapter 5 extends the discussion and concludes the thesis. The chapter 6 contains the bibliographic references. The results of the work suggest that electric oscillations in the olfactory system could be generated in several structures and organizational levels, including the molecular level, the cellular and neural systems level. In particular, the results shown that chemical and electric synapses, as well as the respiratory rhythm, may have a fundamental role in the generation of these oscillations. Indeed, the constructed model proposes a plausible explanation for the origin of the electrical oscillations in the vertebrate olfactory system and discusses the possible function of these oscillations in the context of sensorial information processing.

The aim of the studies included in the thesis is to better understand the interplay between neuronal activity-dependent gene regulation and the bioactive vitamin A metabolite all-trans-retinoic acid (RA) during postnatal development, refinement and maintenance of precise neuronal connectivity using the olfactory sensory neuron (OSN) in the olfactory epithelium (OE) of genetically modified mice as a model. We show that: Inhibition of RA receptor (RAR)-mediated transcription in OSNs reduces expression of the olfactory cyclic nucleotide-gated (CNG) ion channel, which is required for odorant receptor (OR)-mediated stimulus transduction. This, results in increased OSN death and errors in precise connectivity. The increased cell death may be a consequence of reduced intrinsic excitability and/or reduced influx of Ca2+ ions while the errors in connectivity may be due to altered OR-dependent expression of axonal guidance proteins, such as Kirrel-2 and Neuropilin-1. Expression of the RA catabolic enzyme Cyp26B1 in OSNs is positively regulated by RAR-mediated transcription as well as sensory stimulation in a CNG channel-dependent manner. This shows that neuronal activity and local vitamin A metabolism are parts of novel regulatory feedback loop controlling precise connectivity and neuronal survival. The feedback loop may be a form of homeostatic plasticity in response to global changes in neuronal activity. BACE1, an enzyme is implicated in Alzheimer´s disease, and Cyp26B1 are inversely regulated by CNG channel-dependent sensory stimulation. Cyp26B1 expression is switched on at birth, forms a topographic expression gradient in OE and inhibits BACE1 expression into an inverse counter gradient. Taken together these results reveal a novel neuronal activity-dependent mechanism by which sensory stimuli can shape spatial gene expression via altered RA bioavailability. Increased Cyp26B1 expression stimulates turnover of OSNs during adult neurogenesis by a non-cell-autonomous mechanism. The gradient of Cyp26B1 expression correlates with spatially-regulated diversification of OSNs into subpopulations that express different subsets of OR genes. Cyp26B1 expression influences spatial OR diversification of OSNs by two different mechanisms. In the ventrolateral OE, Cyp26B1 inhibits OR expression by blocking OSN differentiation at a stage that may be associated with the cell intrinsic mechanism regulating OR gene choice. In the dorsomedial OE the expression frequency of some ORs is unaltered while other increases, presumably as a consequence of neuronal activity-dependent competition. A probable function of graded and activity-dependent Cyp26B1 expression is to form a topographic partitioning of the olfactory sensory map into functional domains, which gradually differ from each other with regard to experience-driven plasticity and neurogenic potential along the dorsomedial-ventrolateral axis of OE.

Os odores são detectados por uma grande família de receptores olfatórios (ORs) que são expressos nos neurônios olfatórios localizados no nariz. Os ORs ativados por um determinado odor acoplam-se à proteína Galfaolf que irá promover a ativação da adenilil ciclase III, resultando na produção de AMPc. O aumento da concentração de AMPc irá ativar canais iônicos dependentes de AMPc, tendo como consequência a despolarização do neurônio olfatório. A informação desencadeada pela ativação de determinados ORs é então transmitida para regiões específicas do cérebro promovendo a percepção do odor. A determinação da especificidade dos ORs para diferentes odores irá contribuir para o entendimento de como os odores são discriminados pelo sistema olfatório, entretanto, poucos ORs tiveram seus ligantes definidos devido a dificuldade de expressão funcional de ORs em sistema heterólogo. Em nosso trabalho, utilizamos o sistema de duplo-híbrido em levedura a fim de determinar potenciais novos reguladores para Galfaolf. Deste experimento, identificamos que Ric-8B (Ric, abreviatura de Resistant to Inhibitors of Cholinesterase), um provável GEF (GTP Exchange Factor), é capaz de interagir com Gaolf. Assim como Gaolf, Ric-8B é predominantemente expresso nos neurônios olfatórios maduros e em regiões específicas do cérebro. A restrita co-localização de Gaolf e Ric-8B fortemente indica que Ric-8B é uma proteína que participa da via de transdução de sinal de Galfaolf. Através de nossos ensaios, utilizando células HEK-293, foi possível mostrar que Ric-8B é capaz de potencializar a atividade de Galfaolf, tendo como consequência o aumento da produção de AMPc em sistema heterólogo. Por fim, nós mostramos que Ric-8B é capaz de promover a expressão funcional de ORs em sistema heterólogo. Nossos resultados demonstram que a expressão de Ric-8B é capaz de aumentar o acúmulo de Galfaolf na periferia de células HEK-293T, indicando que Ric-8B promove a expressão funcional de ORs provavelmente através da melhora da eficiência do acoplamento dos ORs com Galfaolf. Nossos resultados demonstram que o uso de Ric-8B em um sistema em larga escala irá permitir a expressão funcional de diversos ORs, permitindo a identificação de seus respectivos ligantes. Tal análise irá contribuir para o melhor entendimento do mecanismo de percepção dos odores. / Odorants are detected by a large family of odorant receptors (ORs) expressed in the olfactory neurons in the nose. The activated receptors couple to an olfactory-specific G-protein (Galphaolf), which activates adenylyl cyclase III to produce cAMP. Increased cAMP levels activate cyclic nucleotide-gated channels, causing cell membrane depolarization. The information provided by the odorant receptors is transmitted to specific regions of the brain leading to odorant perception. The determination of the odorant specificities of the different ORs will contribute to the understanding of how odorants are discriminated by the olfactory system. However, only a few ORs have been linked to odorants they recognized to date because ORs are not efficiently expressed in heterologous cells since they are poorly expressed on the cell surface. Here we used yeast two-hybrid to search for potential regulators for Galphaolf. We found that Ric-8B (for Resistant to Inhibitors of Cholinesterase), a putative GTP exchange factor, is able to interact with Gaolf. Like Gaolf, Ric-8B is predominantly expressed in the mature olfactory sensory neurons and also in a few regions in the brain. The highly restricted and colocalized expression patterns of Ric-8B and Galphaolf strongly indicate that Ric-8B is a functional partner for Galphaolf. We show that Ric-8B is able to potentiate Galphaolf-dependent cAMP accumulation in human embryonic kidney 293 cells and therefore may be an important component for odorant signal transduction. Finally, we show that Ric-8B promotes efficient heterologous expression of ORs. Our results show that Ric-8B enhances accumulation of Galphaolf at the cell cortex, indicating that it promotes functional OR expression probably by improving the efficiency of OR coupling to Galphaolf. Our results demonstrate that the employment of Ric-8B in a high-throughput system will allow the functional screening of the OR family members and thereby provide further insight into the mechanisms of odor perception.

Chez les mammifères, le système olfactif principal est fonctionnel dans le dernier tiers du stade gestationnel. Le fœtus est donc capable de détecter avec sensibilité, discriminer, et mémoriser les odorants présents dans le liquide amniotique dans lequel il baigne. Chez le rongeur, ces odorants mémorisés in utero sont fondamentaux pour la survie du nouveau-né à la naissance en lui permettant de s’orienter vers la mamelle et de déclencher la tétée. Par la suite, ces odorants vont guider le nouveau-né dans ses choix olfactifs et alimentaires et favoriser ses apprentissages ultérieurs. Or, on sait que l’alimentation de la mère fait varier les clés olfactives des fluides biologiques (liquide amniotique, lait) et donc modifie la nature des sources olfactives rencontrées par le fœtus, puis le nouveau-né dans la période périnatale. Dans le but d’évaluer l’impact d’une exposition odorante périnatale sur le fonctionnement et la maturation du système olfactif en relation avec le développement de préférences médiées par l’olfaction et la modulation du stress au moment du sevrage, nous avons mis en place un modèle d’exposition odorante périnatale via l’alimentation maternelle dans une lignée transgénique murine exprimant le récepteur olfactif I7 couplé à une protéine fluorescente, dont l’odorant préférentiel est l’heptanal. Après validation de la présence d’heptanal dans le liquide amniotique et le lait de ces souris par GC-MS-MS, nos résultats montrent que l’exposition périnatale à l’heptanal entraine une augmentation significative du nombre de glomérules I7 présents au niveau du bulbe olfactif à PN12 par rapport aux animaux contrôles sans modification notable de l’homéostasie tissulaire ou de la transcription du gène I7 au niveau de la muqueuse olfactive. Ce changement structural important au niveau des projections axonales du bulbe olfactif s’accompagne d’un faible effet sur le comportement olfactif des souriceaux dont les capacités de discrimination ne sont que très faiblement améliorées par rapport aux souriceaux non exposés. A PN21, l’effet de l’exposition odorante sur le nombre de glomérules I7 est atténué, mais reste significatif. A ce stade, les souriceaux odorisés montrent une attraction olfactive pour l’heptanal par rapport au groupe contrôle non exposé, bien que l’effet sur un choix entre aliment odorisé ou pas soit plus contrasté. D’un point de vue moléculaire, ces effets sont associés à une diminution de l’expression du récepteur I7, et de gènes de la signalisation neuronale pouvant traduire une modification de la dynamique cellulaire. Et comme le montrent les résultats obtenus en électro-olfactogramme à cet âge, la sensibilité de la muqueuse olfactive vis-à-vis de l’heptanal est diminuée alors qu’elle ne l’est pas pour d’autres composés odorants. Ces travaux montrent que l’exposition périnatale à un odorant s’accompagne d’effets précoces sur le système olfactif qui impactent son organisation et d’effets sur les choix olfactifs qui se renforcent au cours du développement. Enfin, l’effet d’une exposition périnatale à l’heptanal sur la réponse à des conditions stressantes après séparation maternelle au moment du sevrage a été évaluée en enregistrant des souriceaux CD1 élevés dans les mêmes conditions d’odorisation que les souriceaux mI7-GFP adoptés, en open-field odorisé ou non. Nous avons montré que la réaction de stress des souriceaux à PN21, exposés en périnatal à l’heptanal, dans l’open field, est atténuée lorsque l’heptanal est présent dans l’environnement, comparé à la réaction des souriceaux non exposés qui affichent un comportement d’anxiété. Dans l’ensemble, cette étude a donc permis de mettre en évidence les conséquences en terme d’effets comportementaux (préférences médiées par l’olfaction et diminution du stress), structuraux et moléculaires, d’une exposition odorante périnatale chez le jeune, à l’aide d’une lignée transgénique pour laquelle nous disposions de peu de données. / In mammals, the main olfactory system displays all the structural and functional characteristics at the last third of the gestational stage. Thus, the fetus is able to detect, to discriminate, but also to memorize the odorants present in the amniotic fluid in which it bathes. In the rodent, these odors memorized in utero are fundamental for the survival of the newborn at birth by allowing it to trend itself towards food sources. Afterwards, odorants are guiding the newborn to olfactory and food choices and are promoting subsequent learning. It is known that the mother's diet varies the olfactory keys of the biological fluids (amniotic fluid, milk) and thus modifies the nature of the olfactory sources encountered by the fetus and then the newborn in the perinatal period. The neuroanatomic and functional consequences of this impregnation are the subject of recent studies. The objective of this thesis was to characterize the effects of perinatal odor exposure on the maturation and functioning of the olfactory system in relation to the development of olfactory preferences and to a stressing challenge at weaning. For that, we set up a model of perinatal odor exposure through maternal feeding in the mI7-GFP murine transgenic strain expressing the olfactory receptor I7 coupled with the Green Fluorescent Protein (GFP). We evaluated the neuroanatomic, molecular and behavioral consequences on the pups before weaning, and their evolution over time by focusing our efforts on the postnatal stages 3 (PND3), PND12-14 and PND21. Due to the fragility of the transgenic strain, we worked on mI7-GFP mice pups crossfostered by CD1 mice mothers raised under the same conditions after having validated the presence of heptanal in the amniotic fluid of mI7-GFP mice and the milk of CD1 mice by GC-MSMS. We characterized the effects of perinatal odor exposure on the maturation and functioning of the olfactory system in relation to the olfactory preference until weaning (mI7-GFP mice pups under CD1 adoptive mothers) and on the stress reaction to maternal separation at weaning (CD1 mice pups under biological mother). Our results show that perinatal exposure to heptanal leads to a significant increase in the number of I7 glomeruli in the olfactory bulb (OB) associated to a slight modification of the tissue homeostasis in the olfactory mucosa (OM) and to subtle differencies in heptanal sensitivity and preferences, that are amplified at PND21. From a molecular point of view, these effects are associated to a down-regulation of the expression of the I7 receptor and genes of neuronal signaling and an odorantspecific decrease in EOG response which may highlight a modification of the cellular dynamics. Finally, the effect of perinatal exposure to heptanal on the response to stressing conditions after maternal separation was assessed by recording CD1 mice pups grown under the same conditions than fostered mi7 mice on odorized and non odorized open-field. We showed that the reaction of odorized mice in the open field at PND21 is attenuated when the odorant is present in the environment, compared to non odorized mice that display anxiety-like behavior. Overall, this study demonstrates the consequences of a perinatal odorant exposure in the young, in terms of behavior (olfactory preference and anxiety), structural and molecular plasticity of the olfactory system, on a transgenic strain for which we had little available data.

付記する学位プログラム名: 京都大学大学院思修館 / 京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第20432号 / 農博第2217号 / 新制||農||1048(附属図書館) / 学位論文||H29||N5053(農学部図書室) / 京都大学大学院農学研究科食品生物科学専攻 / (主査)教授 保川 清, 教授 河田 照雄, 准教授 井上 和生 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

The olfactory system is believed to be the oldest sensory system. It developed to detect and analyse chemical information in the form of odours, and its organisation follows the same principles in almost all living animals - insects as well as mammals. Likely, the similarities are due to parallel evolution - the same type of organisation has arisen more than once. Therefore, the olfactory system is often assumed to be close to optimally designed for its tasks. Paradoxically, the workings of the olfactory system are not yet well known, although several milestone discoveries have been made during the last decades. The most well-known is probably the disovery of the olfactory receptor gene family, announced in 1991 by Linda Buck and Richard Axel. For this and subsequent work, they were awarded a Nobel Prize Award in 2004. This achievement has been of immense value for both experimentalists and theorists, and forms the basis of the current understanding of olfaction. The olfactory system has long been a focus for scientific interest, both experimental and theoretical. Ever since the field of computational neuroscience was founded, the functions of the olfactory system have been investigated through computational modelling. In this thesis, I present the basis of a biologically realistic model of the olfactory system. Our goal is to be able to represent the whole olfactory system. We are not there yet, but we have some of the necessary building blocks; a model of the input from the olfactory receptor neuron population and a model of the olfactory bulb. Taking into account the reported variability of geometrical, electrical and receptor-dependent neuronal characteristics, we have been able to model the frequency response of a population of olfactory receptor neurons. By constructing several olfactory bulb models of different size, we have shown that the size of the bulb network has an impact on its ability to process noisy information. We have also, through biochemical modelling, investigated the behaviour of the enzyme CaMKII which is known to be critical for early olfactory adaptation (suppression of constant odour stimuli). / Luktsystemet anses allmänt vara det äldsta sensoriska systemet. Det utvecklades för att upptäcka och analysera kemisk information i form av lukter, och det är organiserat efter samma principer hos nästan alla djurarter: insekter så väl som däggdjur. Troligen beror likheterna på parallell evolution -- samma organisation har uppstått mer än en gång. Därför antas det ofta att luktsystemet är nära optimalt anpassat för sina arbetsuppgifter. Paradoxalt nog är luktsystemets arbetssätt ännu inte väl känt, även om flera banbrytande framsteg gjorts de senaste decennierna. Det mest välkända är nog upptäckten av genfamiljen av luktreceptorer, som tillkännagavs 1991 av Linda Buck och Rikard Axel. För detta och efterföljande arbete belönades de med Nobelpriset år 2004. Upptäckten har varit mycket värdefull för både experimentalister och teoretiker, och formar grunden för vår nuvarande förståelse av luktsystemet. Luktsystemet har länge varit ett fokus för vetenskapligt intresse, både experimentellt och teoretiskt. Ända sedan fältet beräkningsbiologi grundades har luktsystemet undersökts genom datormodellering. I denna avhandling presenterar jag grunden för en biologiskt realistisk modell av luktsystemet. Vårt mål är att kunna representera hela luktsystemet. Så långt har vi ännu inte nått, men vi har några av de nödvändiga byggstenarna: en modell av signalerna från populationen av luktreceptorceller, och en modell av luktbulben. Genom att ta hänsyn till nervcellernas rapporterade variationer i geometriska, elektriska och receptor-beroende karaktärsdrag har vi lyckats modellera svarsfrekvenserna från en population av luktreceptorceller. Genom att konstruera flera olika stora modeller av luktbulben har vi visat att storleken på luktbulbens cellnätverk påverkar dess förmåga att behandla brusig information. Vi har också, genom biokemisk modellering, undersökt beteendet hos enzymet CaMKII, som är kritiskt viktigt för adaptering (undertryckning av ständigt närvarande luktstimuli) i luktsystemet.

<p>Sensory neuron diversity is a common theme in the animal kingdom. It provides the cellular infrastructure that supports the accurate perception of the external world. Among all sensory systems, the olfactory system demonstrates an extreme in the extraordinarily diversified neuronal classes it holds. The system-wide cellular diversity is in sharp contrast with the individual specialization of olfactory receptor neurons (ORNs) per se. How the nervous system, particularly the olfactory system, uses limited genetic information to generate a huge variety of neurons with distinct properties remains elusive. </p><p>The adult Drosophila olfactory system is an excellent model to address this question due to its conserved organizational principles and reduced complexity. The fly olfactory appendages contain 50 ORN classes, each of which expresses a single receptor gene from a family of ~80 genes. Stereotyped clusters of 1-4 ORN classes define about 20 sensilla subtypes, belonging to 3 major morphological types. All cellular components within a sensillum are born by a single sensory organ precursor (SOP) via asymmetric divisions. The molecular mechanisms that determine SOP differentiation potentials to develop into distinct sensilla subtypes and the associated ORN classes are unknown.</p><p>From a genetic screen, we identified two mutant alleles in the rotund (rn) gene locus, which has a critical function in diversifying ORN classes. Rn is required in a subset of SOPs to confer novel sensilla subtype differentiation potentials from otherwise default ones within each sensilla type lineage. In rn mutants, ORNs in rn-positive sensilla subtypes are converted to lineage-specific default rn-negative fates, resulting in only half of the normal ORN diversity. This work is described in Chapter 2.</p><p>Based on an unbiased time-course transcriptome analysis, we discovered two critical downstream targets of Rn, Bric-à-brac (Bab) and Bar. In light of the knowledge about leg development, we found these genes, along with Apterous (Ap) and Dachshund (Dac), are part of the conserved proximal-distal (PD) gene network that play a crucial role in patterning the antennal precursor field prior to proneural gene-mediated SOP selection. Interactions between these PD genes under the influence of morphogen gradients separate the developing antennal disc into 7 concentric domains. Each ring is represented by a unique combination of the aforementioned transcription factors, coding the differentiation potentials for a limited number of sensilla subtypes. Genetic perturbations of the network lead to predictable changes in the ratios of different sensilla subtypes and corresponding ORN classes. In addition, using CRISPR/Cas9 technology, we were able to add tags to specific rn isoforms in the endogenous locus, and show positive regulation of Bab and negative regulation of Bar by the direct binding of Rn to the promoters in vivo. This work is presented in Chapter 3.</p><p>We proposed a three-step mechanism to explain ORN diversification, starting from pre-patterning of the precursor field by PD genes, followed by SOP selection by proneural genes, and ended with Notch-mediated neurogenesis. The final outcomes are greatly determined by the pre-patterning phase, which may be modified during evolution to compensate special olfactory needs by individual species. In our model, each step serves a single purpose, which displays context-dependent functions. By changing contexts, reassembly of the same logical steps may guide neuronal diversification in parallel systems with completely different identities. This step-wise mechanism seems to be a common strategy that is used by many other systems to generate neuronal diversity.</p> / Dissertation

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.