Estudos realizados na última década mostram que a substância P (SP) é um neuromediador importante de estados emocionais e afetivos. A SP tem ação pró-aversiva quando microinjetada na substância cinzenta periaquedutal dorsal (SCPd) através da ativação de receptores neurocininérgicos do tipo NK-1, uma vez que o comportamento defensivo é bloqueado por antagonistas desses receptores. A ativação de receptores NK-1 na SCPd também produz antinocicepção, a qual é considerada parte da reação de defesa. Na sequência desses estudos, este projeto visa investigar o envolvimento dos receptores neurocininérgicos no núcleo central (CeA) e basolateral (BLA) da amígdala na mediação dos estados aversivos gerados e elaborados nessa estrutura prosencefálica que, junto com a SCPd, faz parte do sistema encefálico aversivo. O presente estudo mostrou que a SP e o agonista NK-1 (Sar-Met-SP) promoveram efeitos pró-aversivos no labirinto em cruz elevado somente no CeA, mas não no BLA. Ao contrário da SCPd, não obtivemos qualquer alteração no limiar nociceptivo com a microinjeção de antagonista de receptores NK-1 (Spantide) em ambos os núcleos. O Spantide sozinho não alterou os indicadores de nocicepção e ansiedade. Nenhum tipo de vocalização (audível ou ultrassônica) foi detectado no presente trabalho após a microinjeção de SP ou Sar-Met-SP em ambos núcleos amigdalóides, apesar de relatos de vocalizações ultrassônicas (VUS) após o mesmo tipo de tratamento na SCPd. Os resultados obtidos no presente estudo mostraram que o CeA, mas não o BLA, modula a expressão de comportamentos relacionados ao medo inato através de receptores neurocininérgicos do tipo NK-1. VUS e antinocicepção não parecem participar da reação de defesa elaborada no CeA. A ausência da emissão de VUS nesses núcleos pode indicar que somente estruturas mais antigas do neuroeixo (mesencéfalo e hipotálamo) são responsáveis pela produção de VUS. / A substantial body of evidence obtained in the last decade demonstrated that the Substance P (SP) is an important mediator of the affective and emotional behaviors. SP is a pro-aversive compound when microinjected within the dorsal periaqueductal gray (dPAG). These effects are mediated by the type 1 neurokininergic receptors (NK-1), since the defensive behavior was inhibited by antagonists of these receptors. The activation of NK-1 receptors in the dPAG also produced antinociception and ultrasonic vocalizations (USV). In the sequence of these studies, this study investigated the involvement of neurokinin receptors of the central (CeA) and basolateral (BLA) nuclei of the amygdala in the mediation of the defense reaction. The amigdala together with the dPAG and the medial hypothalamus comprise the encephalic aversive system. The results showed that SP and the NK-1 agonist (Sar-Met-SP) promoted pro-aversive effects in the elevated plus maze test only when microinjected into the CeA, without effect in the BLA. Although SP and the activation of NK-1 receptors induce antinociception in the dPAG, we did not observe any alteration of the nociceptive threshold in the tail-flick test with the NK-1 antagonist (Spantide) injected into both nuclei and any changes of the anxiety parameters in the EPM. No vocalizations (audible or ultrasonic) were detected after treatment with SP or Sar-Met-SP in both amygdaloid nuclei. The lack of emissions of USVs after activation of these nuclei could indicate that only older structures (PAG and hypothalamus) of the neuroaxis are responsible for the production of USVs. The results obtained in the present study show that NK-1 receptors within CeA, but not BLA, modulate the expression of defensive behaviors related to the innate fear. Apparentely USVs and antinociception are not involved in the defensive reactions indiced by activation of NK-1 mechanisms in the CeA.

Estudos realizados na última década mostram que a substância P (SP) é um neuromediador importante de estados emocionais e afetivos. A SP tem ação pró-aversiva quando microinjetada na substância cinzenta periaquedutal dorsal (SCPd) através da ativação de receptores neurocininérgicos do tipo NK-1, uma vez que o comportamento defensivo é bloqueado por antagonistas desses receptores. A ativação de receptores NK-1 na SCPd também produz antinocicepção, a qual é considerada parte da reação de defesa. Na sequência desses estudos, este projeto visa investigar o envolvimento dos receptores neurocininérgicos no núcleo central (CeA) e basolateral (BLA) da amígdala na mediação dos estados aversivos gerados e elaborados nessa estrutura prosencefálica que, junto com a SCPd, faz parte do sistema encefálico aversivo. O presente estudo mostrou que a SP e o agonista NK-1 (Sar-Met-SP) promoveram efeitos pró-aversivos no labirinto em cruz elevado somente no CeA, mas não no BLA. Ao contrário da SCPd, não obtivemos qualquer alteração no limiar nociceptivo com a microinjeção de antagonista de receptores NK-1 (Spantide) em ambos os núcleos. O Spantide sozinho não alterou os indicadores de nocicepção e ansiedade. Nenhum tipo de vocalização (audível ou ultrassônica) foi detectado no presente trabalho após a microinjeção de SP ou Sar-Met-SP em ambos núcleos amigdalóides, apesar de relatos de vocalizações ultrassônicas (VUS) após o mesmo tipo de tratamento na SCPd. Os resultados obtidos no presente estudo mostraram que o CeA, mas não o BLA, modula a expressão de comportamentos relacionados ao medo inato através de receptores neurocininérgicos do tipo NK-1. VUS e antinocicepção não parecem participar da reação de defesa elaborada no CeA. A ausência da emissão de VUS nesses núcleos pode indicar que somente estruturas mais antigas do neuroeixo (mesencéfalo e hipotálamo) são responsáveis pela produção de VUS. / A substantial body of evidence obtained in the last decade demonstrated that the Substance P (SP) is an important mediator of the affective and emotional behaviors. SP is a pro-aversive compound when microinjected within the dorsal periaqueductal gray (dPAG). These effects are mediated by the type 1 neurokininergic receptors (NK-1), since the defensive behavior was inhibited by antagonists of these receptors. The activation of NK-1 receptors in the dPAG also produced antinociception and ultrasonic vocalizations (USV). In the sequence of these studies, this study investigated the involvement of neurokinin receptors of the central (CeA) and basolateral (BLA) nuclei of the amygdala in the mediation of the defense reaction. The amigdala together with the dPAG and the medial hypothalamus comprise the encephalic aversive system. The results showed that SP and the NK-1 agonist (Sar-Met-SP) promoted pro-aversive effects in the elevated plus maze test only when microinjected into the CeA, without effect in the BLA. Although SP and the activation of NK-1 receptors induce antinociception in the dPAG, we did not observe any alteration of the nociceptive threshold in the tail-flick test with the NK-1 antagonist (Spantide) injected into both nuclei and any changes of the anxiety parameters in the EPM. No vocalizations (audible or ultrasonic) were detected after treatment with SP or Sar-Met-SP in both amygdaloid nuclei. The lack of emissions of USVs after activation of these nuclei could indicate that only older structures (PAG and hypothalamus) of the neuroaxis are responsible for the production of USVs. The results obtained in the present study show that NK-1 receptors within CeA, but not BLA, modulate the expression of defensive behaviors related to the innate fear. Apparentely USVs and antinociception are not involved in the defensive reactions indiced by activation of NK-1 mechanisms in the CeA.

Extensos dados na literatura têm assinalado a importância da serotonina (5-HT) na modulação de comportamentos de medo e ansiedade em roedores, a grande maioria utilizando ratos machos como sujeitos experimentais. No presente trabalho, foi analisada a influência da neurotransmissão 5-HT periférica e central sobre a expressão da resposta de medo condicionado e incondicionado de ratos machos e fêmeas, previamente selecionados pelo fenótipo como animais de baixa (BA) ou de alta (AA) reatividade emocional. Para este fim foi utilizado o teste do sobressalto potencializado pelo medo (SPM). A influência global e central de 5-HT foi avaliada pela utilização da administração sistêmica ou intraventricular aguda do inibidor irreversível da enzima triptofano hidroxilase PCPA (p-clorofenilalanina) nas doses de 200 mg/mL (i.p.) e 200 µg/5 µL (i.v.), ou através de infusões locais de 5-HT (10 nmol/0.2 µL) ou do agonista seletivo de receptores 5-HT1A 8-hidroxi-2-(di-n-propilamino)-tetralina (8-OH-DPAT) na dose de 0,3 µg/0.2 µL, diretamente em áreas encefálicas conhecidas por sua influência na modulação do medo e ansiedade a saber: o córtex pré-limbico (CPL), o núcleo basolateral da amígdala (BLA), e a substância cinzenta periaqueductal dorsal (SCPd) do mesencéfalo. As variáveis dependentes registradas foram a amplitude e a latência das respostas incondicionadas e condicionadas de sobressalto e a amplitude do SPM. / Extensive data in the literature have signaled the importance of serotonin (5-HT) on the modulation of fear and anxiety-like behaviors in rodents. In the present study, we have analyzed the influence of peripheral and central 5-HT neurotransmission on the expression of the conditioned and unconditioned fear, and on the fear-potentiated startle in male and female rats previously selected as low- (LA) or high-anxiety (HA). For this purpose, we used the fear-potentiated startle (FPS) test. The global and central influence of 5-HT was evaluated by using the acute systemic or intraventricular administration of the irreversible tryptophan hydroxylase inhibitor PCPA (p-chlorophenylalanine - 200 mg/mL i.p., or 200 µg/5 µL i.v.). Local effects were evaluated through local infusions of 5-HT itself (10 nmol/0.2 µL) or the selective 5-HT1A receptors agonist 8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT 0.3 µg/0.2 µL) in the prelimbic cortex (PrL), basolateral amygdala (BLA) or the dorsal periaqueductal gray (DPAG). These brain regions were chosen for the present study based on their great importance in the modulation and expression of conditioned and unconditioned fear. Dependent variables recorded were the amplitude and latency of unconditioned and conditioned fear, and fear-potentiated startle (FPS).

Introduction: Microbial fermentation of carbohydrates in forestomach of ruminants produces large amounts of short-chain fatty acids (SCFA, mainly acetic acid, propionic acid, and n-butyric acid). The majority of these substrates is taken up directly across the ruminal wall. After luminal uptake into the epithelial cells, SCFA mainly occur in the dissociated form due to the intracellular pH of ~7.4. Moreover, a big portion of SCFA is metabolised within the cytosol. Main end products of epithelial SCFA metabolism are ketone bodies (D-3-hydroxybutyric acid and acetoacetic acid) and lactic acid. Both intact SCFA and ketone bodies and lactate need to be efficiently extruded from the ruminal epithelial cells to prevent a lethal drop of intracellular pH and counteract osmotic load of the cytosol. All these substances are less lipophilic in comparison to the undissociated form of SCFA. Thus, dissociated SCFA (SCFA-) and their metabolites need Protein mediated mechanisms for the extrusion across the basolateral side of ruminal epithelium. One mechanism suggested to be involved in the extrusion of SCFA- across basolateral membrane of the ruminal epithelium is the monocarboxylate transporter 1 (MCT1). Functionally, MCT1 was first assumed to operate as proton-coupled transporter for monocarboxylates including SCFA. Nonetheless, a recent study found a bicarbonate dependent anion exchange mechanism which turned out to be sensitive to MCT1 Inhibitors at the basolateral side of the ruminal epithelium pointing to the ability of MCT1 to act as an anion exchanger. However, in these experiments the inhibition of MCT1 abolished bicarbonate dependent transport only by half. This suggests the involvement of further anion exchanger(s) in the transport of SCFA across the basolateral membrane of ruminal epithelium. Promising candidates to underlie this exchange are the putative Anion exchanger 1 (PAT1) and a transport protein designated „down-regulated in adenoma“ (DRA). Materials and Methods: Sheep rumen epithelium was mounted in Ussing Chambers under short-circuit conditions. Radioactively labelled acetate (ac) was added to the serosal side. Serosal to mucosal flux of ac (Jsm ac) was measured with or without anion Exchange inhibitors (50 mM NO3- or 1 mM DIDS) or the MCT1 inhibitor p-hydroxy mercuribenzoic acid (pHMB; 1.5 mM) in the serosal buffer solution. The inhibitors were added alone or in combination with each other. Furthermore, mucosal to serosal flux of radioactivelly labelled ac or butyrate (bu) (Jms ac, bu) was measured in the presence or absence of SO42-, Cl- or NO3- (50 mM respectively) as exchange substrate in the serosal buffer solution. Immunohistochemical staining was conducted to locate PAT1 and DRA by use of commercially available antibodies. Results: NO3- and pHMB significantly reduced Jsm ac by 57 % and 51 %, respectively. When pHMB was applied after pre-incubation with NO3- an additional inhibition of Jsm ac was observed. Vice versa, NO3- further inhibited Jsm ac when epithelia were pre-incubated with pHMB before. DIDS had no inhibitory effect on SCFA flux. Serosal presence of SO42- or Cl- enhanced Jms ac significantly. Regarding bu, Cl- or SO4 2- also enhanced Jms bu significantly. The different anions available in the serosal buffer solution numerically enhanced Jms in the order of SO4 2- > Cl- for both ac and bu, which corresponds to the known affinity sequence of PAT1 and DRA. Immunohistochemistry revealed localization of PAT 1 in the stratum basale, whereas DRA was not detectable using this method. Conclusions: Basically, this study supports the suggestion that MCT1 works as an Anion exchanger in ruminal epithelium. In addition, it clearly shows that there is at least one further anion exchanger involved in the basolateral extrusion of SCFA and their metabolites. The functional and immunohistochemical findings suggest that PAT1 holds a significant role in this respect.

L’amygdale est une structure du système nerveux central impliquée dans l’intégration des émotions comme la peur et l’anxiété. Des études ont également montré que l’amygdale peut moduler de façon positive ou négative la douleur par le biais des projections de son noyau de sortie, le noyau central de l’amygdale (CeA), sur les structures impliquées dans les contrôles nociceptifs descendants. Le complexe basolatéral de l’amygdale (BLA), placé en amont du noyau central, est intimement connecté à ce dernier et peut ainsi réguler son fonctionnement. Les données obtenues au cours de ma thèse ont montré l’existence d’un contrôle tonique amygdalien de la nociception et de la douleur, directement dépendant de l’équilibre entre l’excitation et l’inhibition au sein de la structure. Ainsi la modulation de l’une ou l’autre des neurotransmission influence directement la sortie douloureuse, chez des animaux sains ou neuropathiques. Par ailleurs, nous nous sommes également intéressés à l’étude précise du mode d’action d’une molécule anxiolytique non benzodiazépinique, l’étifoxine (EFX), et à son effet sur le comportement douloureux. Les résultats des injections d’EFX dans le BLA indiquent qu’elle induit une action analgésique chez les animaux neuropathiques, mais ne modifie pas les seuils de sensibilité des animaux sains. Cette action analgésique est dépendante de l’effet indirect neurostéroïdogène de l’EFX. Ceci, associé au fait que l’EFX ne présente pas ou peu d’effets secondaires, en fait une molécule particulièrement intéressante pour un traitement alternatif des douleurs neuropathiques. Dans une dernière partie, nous avons cherché à observer les mécanismes en jeu au niveau cellulaire lorsque l’EFX est appliquée sur les neurones du BLA. Ainsi, nous avons montré que l’EFX potentialise l’inhibition au sein de la structure, via trois mécanismes indépendants ; l’augmentation de la fréquence des courants post-synaptiques inhibiteurs miniatures (mCPSIs), l’augmentation de leur amplitude, et l’augmentation de leur constante de déactivation. Ces deux derniers effets sont dépendants de l’action neurostéroïdogène de l’EFX, tandis que l’effet sur la fréquence des mCPSIs est du à l’action de l’EFX sur le récepteur GABAA. Les résultats de ma thèse ont ainsi permis de montrer l’existence d’un contrôle tonique amygdalien de la douleur, dans le cadre d’animaux neuropathiques, mais également de la nociception, chez des animaux sains. Par ailleurs, la place du complexe basolatéral de l’amygdale, souvent peu prise en compte dans les études sur la douleur, a été redéfinie. Ce complexe doit être pris en considération dans le circuit de la douleur et son rôle de pilote du noyau central de l’amygdale ne doit pas être négligé. / The amygdala is a major control center of the emotions, but also integrates sensory, especially nociceptive information. Cortical afferents to the amygdala largely target its basolateral complex. The basolateral amygdala (BLA) then projects to the central amygdala nucleus, which in turn projects densely to the periaqueductal gray and thus can drive a behavioural output via the spinal cord. Data obtained during my thesis have shown that the balance between excitation and inhibition in the BLA triggers an tonic control of pain. Therefore modulating one of the neurotransmission directly influences the pain threshold of control or nociceptive mice. My thesis work also focused on the functioning of an anxiolytic and non benzodiazepinic drug ; Etifoxin (EFX). This molecule as a positive modulator of GABAA receptors and indirectly by increasing the synthesis of neurosteroids, also known as strong modulator of these receptors. In our team, we already showed that EFX has anti-nociceptive effects when injected intraperitonealy in rats. Here we wanted to determine the action of EFX on pain descending control drive by BLA. We showed that EFX infusion in the BLA seems to be anti-nociceptive, inducing a recover of the pre-cuff mechanical threshold level. We also used a patch-clamp approach to study directly in vitro the modulation of the inhibitory synaptic transmission produced by EFX. We showed that EFX potentiate the inhibition in BLA neurons via different and complementary mechanisms. These potentiating effects are mostly dependent of a neurosteroidogenesis increase.

Indiana University-Purdue University Indianapolis (IUPUI) / Anxiety disorders are estimated to impact 1 in 4 individuals within their lifetime. For some individuals, repeated episodes of the stress response leads to pathological anxiety and depression. The stress response is linked to increased levels of corticotropin-releasing factor (CRF) in the basolateral nucleus of the amygdala (BLA), a putative site for regulating anxiety and associative processes related to aversive emotional memories, and activation of CRF receptors in the BLA of rats produces anxiety-like behavior. Mimicking repeated episodes of the stress response, sub-anxiogenic doses of urocortin 1 (Ucn1), a CRF receptor agonist, are microinjected into the BLA of rats for five consecutive days, a procedure called priming. This results in 1) behavioral sensitization, such that a previously non-efficacious dose of Ucn1 will elicit anxiety-like response after the 3rd injection and 2) the development of a persistent anxiety-like phenotype that lasts at least five weeks after the last injection without any further treatment. Therefore, the purpose of this thesis was to identify mechanisms involved in the Ucn1-priming-induced anxiogenesis. The first a set of experiments revealed that the anxiety-like behavior was not due to aversive conditioning to the context or partner cues of the testing environment. Next, Ucn1-priming-induced gene expression changes in the BLA were identified: mRNA expression for Sst2, Sst4, Chrna4, Chrma4, and Gabrr1 was significantly reduced in Ucn1-primed compared to Vehicle-primed rats. Of these, Sst2 emerged as the primary receptor of interest. Subsequent studies found that antagonizing the Sstr2 resulted in anxiety-like behavior and activation of Sstr2 blocked acute Ucn1-induced anxiety-like responses. Furthermore, pretreatment with a Sstr2 agonist delayed the behavioral sensitization observed in Ucn1-induced priming but did not stop the development of persistent anxiety-like behavior or the Ucn1-priming-induced decrease in the Sstr2 mRNA. These results suggest that the decrease in Sstr2 mRNA is associated with the expression of persistent anxiety-like behavior but dissociated from the mechanisms causing the behavioral sensitization. Pharmacological studies confirmed that a reduced Sstr2 mediated effect in the BLA is likely to play a role in persistent anxiety and should be investigated further.

Social interaction deficits seen in psychiatric disorders emerge in early-life and are most closely linked to aberrant neural circuit function. Due to technical limitations, we have limited understanding of how typical versus pathological social behavior circuits develop. Using a suite of invasive procedures in awake, behaving infant rats, including optogenetics, microdialysis, and microinfusions, we dissected the circuits controlling the gradual increase in social behavior deficits following two complementary procedures-naturalistic harsh maternal care and repeated shock alone or with an anesthetized mother. Whether the mother was the source of the adversity (naturalistic Scarcity-Adversity) or merely present during the adversity (repeated shock with mom), both conditions elevated basolateral amygdala (BLA) dopamine, which was necessary and sufficient in initiating social behavior pathology. This did not occur when pups experienced adversity alone. These data highlight the unique impact of social adversity as causal in producing mesolimbic dopamine circuit dysfunction and aberrant social behavior.

Submitted by PPG Medicina e Ci?ncias da Sa?de (medicina-pg@pucrs.br) on 2017-12-26T13:48:34Z No. of bitstreams: 1 CAROLINA_GARRIDO_ZINN_TES.pdf: 7131704 bytes, checksum: 554f552cadd232d7ef553c1f275476ba (MD5) / Approved for entry into archive by Caroline Xavier (caroline.xavier@pucrs.br) on 2017-12-29T11:25:22Z (GMT) No. of bitstreams: 1 CAROLINA_GARRIDO_ZINN_TES.pdf: 7131704 bytes, checksum: 554f552cadd232d7ef553c1f275476ba (MD5) / Made available in DSpace on 2017-12-29T11:48:08Z (GMT). No. of bitstreams: 1 CAROLINA_GARRIDO_ZINN_TES.pdf: 7131704 bytes, checksum: 554f552cadd232d7ef553c1f275476ba (MD5) Previous issue date: 2017-08-31 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / The social recognition memory (SRM) is crucial to reproduction, formation of social groups and species survival. It is well known that oxytocin, vasopressin, sexual hormones and the olfactory bulb are strongly involved in the formation of SEM. Despite its relevance, the involvement of neurotransmitters such as dopamine (DA), noradrenaline (NE) and histamine (HIS), as well as the brain structures basolateral amygdala (BLA) and CA1 region of dorsal hippocampus ? commonly known for their importance in consolidating and maintaining other types of memories ? remains unknown when concerning SRM. Therefore, the first part of this study aims to evaluate the participation of the D1/D5 dopaminergic, ?-adrenergic and H2 histaminergic receptors into BLA and CA1 on consolidation of SRM. For this, male Wistar adult rats (3 months) were submitted to the social discrimination task (SDT), which is based on the natural tendency of the rodents to explore the novelty. The adult animal was exposed to a juvenile (21 days) conspecific for 1 hour (training session) and 24 hours later to the juvenile previously met (familiar) and to a new juvenile during 5 minutes (test session), when the exploration time was measured. Pharmacological interventions took place immediately after the training session. We verified that the H2 histaminergic receptors are required to the consolidation of SRM both in CA1 and BLA. However, the activation of D1/D5 dopaminergic and ?-adrenergic receptors interferes in an opposite way in the two brain structures: D1/D5 receptors are required in CA1, but not in BLA for consolidation of MRS, whereas activation of ?-adrenergic receptors is indispensable in BLA, but not in CA1. Methylphenidate (MPH) is a drug widely used in the treatment of Attention Deficit Hyperactivity Disorder. It exerts its therapeutic effect by increasing levels of DA and NE in brain structures involved in the learning processes, such as prefrontal cortex (PFC) and hippocampus. Since DA and NE have opposite actions in MRS, we decided to evaluate the effect of MPH on the formation and recall of MRS, since this drug acts on the levels of both neurotransmitters and has been used for academic doping by healthy individuals. Using SDT, with pharmacological interventions at different times, we verified that: 1) MPH, administered acutely prior to the information acquisition, blocked SRM; 2) Blockade was reversed when the animals received MPH at the time of acquisition and retrieval, characterizing the phenomenon known as state dependency (SD) learning; 3) The SD is associated to the CPF, but not to CA1; 4) SD does not depend on CA1, since the increase of NE in CA1 impairs the retrieval of the SRM. In addition, we verified that the 21-day chronic treatment with MPH causes a greater persistence of MRS when a weaker training session is performed. Considering the obtained results, this work demonstrates that the hippocampus, the basolateral amygdala and the prefrontal cortex, modulated by the dopaminergic and noradrenergic systems, regulate the SRM processing. / A mem?ria de reconhecimento social (MRS) ? crucial ? reprodu??o, forma??o de grupos sociais e sobreviv?ncia das esp?cies. Sabe-se que a ocitocina, a vasopressina, os horm?nios sexuais e o bulbo olfat?rio t?m um forte envolvimento na forma??o da MRS. Apesar de sua relev?ncia, a participa??o de neurotransmissores, como dopamina (DA), noradrenalina (NA) e histamina (HIS), bem como das estruturas am?gdala basolateral (BLA) e regi?o CA1 do hipocampo (CA1) ? j? amplamente conhecidos pela sua import?ncia na consolida??o e manuten??o de outros tipos de mem?rias ? permanece desconhecido quanto ? MRS. Sendo assim, a primeira parte deste trabalho buscou avaliar a participa??o dos receptores D1/D5 dopamin?rgicos, ?-adren?rgicos e H2 histamin?rgicos na BLA e CA1 sobre a consolida??o da MRS. Para isso, ratos Wistar machos adultos (3 meses) foram submetidos a tarefa de discrimina??o social (TDS), que baseia-se na tend?ncia natural dos roedores de explorar a novidade. O animal adulto foi exposto a um juvenil (21 dias) coespec?fico por 1 hora (sess?o de treino) e 24 horas depois ao juvenil previamente encontrado (familiar) e a um novo juvenil durante 5 minutos (sess?o de teste), quando o tempo de explora??o foi medido. As interven??es farmacol?gicas ocorreram imediatamente ap?s a sess?o de treino. Verificou-se que os receptores H2 histamin?rgicos s?o necess?rios para a consolida??o da mem?ria tanto em CA1 quanto na BLA. Contudo a ativa??o dos receptores D1/D5 dopamin?rgicos e ?-adren?rgicos interfere de forma oposta nas duas estruturas cerebrais: os receptores D1/D5 s?o necess?rios em CA1, mas n?o na BLA para a consolida??o da MRS, enquanto a ativa??o dos receptores ?adren?rgicos ? indispens?vel na BLA, por?m n?o em CA1. O metilfenidato (MPH) ? um f?rmaco amplamente utilizado no tratamento do Transtorno do D?ficit de Aten??o e Hiperatividade. Exerce seu efeito terap?utico pelo aumento nos n?veis de DA e NA em estruturas cerebrais envolvidas nos processos de aprendizagem, como c?rtex pr?frontal (CPF) e hipocampo. Uma vez que a DA e a NA tem a??es opostas na MRS, decidimos avaliar o efeito do MPH sobre a forma??o e a evoca??o da MRS, j? que esta droga atua sobre os n?veis de ambos os neurotransmissores e tem sido utilizada como doping acad?mico por indiv?duos saud?veis. Utilizando a TDS, com as interven??es farmacol?gicas em diferentes momentos, verificamos que: 1) o MPH, administrado de forma sist?mica aguda previamente ? aquisi??o da informa??o, bloqueou a MRS; 2) O bloqueio foi revertido quando os animais receberam MPH no momento da aquisi??o e da evoca??o, caracterizando o fen?meno conhecido como depend?ncia de estado (DE); 3) A DE ? associada ao CPF, mas n?o a CA1; 4) A DE n?o depende de CA1, pois o aumento de NA em CA1 prejudica a evoca??o da MRS. Al?m disso, verificamos que o tratamento cr?nico de 21 dias com MPH causa uma maior persist?ncia da MRS, quando realizada uma sess?o de treino mais fraca. Considerando os resultados obtidos, este trabalho demonstra que o hipocampo, a am?gdala basolateral e o c?rtex pr?-frontal, modulados pelos sistemas dopamin?rgico e noradren?rgico, regulam o processamento da MRS.

L’objectif de cette thèse est de décrire le réseau cérébral et la dynamique neuronale qui pourraient servir de support aux aversions alimentaires de type olfactives. Nous avons réalisé des enregistrements multisites de potentiel de champ locaux chez le rat vigile engagé dans cet apprentissage, en proposant deux modes de présentation de l’indice olfactif : à proximité de l’eau de boisson (distal) ou ingéré (distal-proximal). Après apprentissage, la présentation du seul indice distal induit l’émergence d’une activité oscillatoire de forte amplitude dans la bande de fréquence beta (15-40 Hz). Finement corrélée au comportement d’aversion de l’animal, cette activité est proposée comme la signature du réseau de structures fonctionnellement impliquées dans la reconnaissance de l’odeur en tant que signal. Nous montrons que ce réseau peut être plus ou moins étendu selon la façon dont le stimulus a été perçu lors du conditionnement: dans certaines aires (bulbe olfactif, cortex piriforme, amygdale basolatérale, cortex orbitofrontal) la modulation en puissance de l’activité beta se fait indépendamment du mode de conditionnement; dans d’autres aires (cortex insulaire, cortex infralimbique) ces changements ont lieu si et seulement si l’odeur a été ingérée. Complétés par l’étude des interactions fonctionnelles entre ces différentes structures dans la bande de fréquence considérée, ces résultats nous permettent de mieux comprendre comment un stimulus peut être représenté en mémoire dans un réseau cérébral en fonction de l’expérience que l’animal en a fait. / The goal of this thesis is to describe the dynamic of the neural network involved in food aversion based on olfactory cue. We performed multisite recordings of local field potential in the behaving rat engaged in such aversion learning and offered two modes of presentation of the olfactory cue: either close to drinking water (distal) or ingested (distal-proximal). After learning, the presentation of the distal cue alone induced the emergence of a powerful oscillation in the beta frequency band (15-40 Hz). Finely correlated with the aversive behavior of the animal, this activity has been proposed as the signature of the neural network functionally involved in odor signal recognition. We showed that this network may be more or less extended depending on how the stimulus has been experienced during conditioning: in some areas (olfactory bulb, piriform cortex, basolateral amygdala, orbitofrontal cortex), modulation of beta power were observed whatever the mode of odor presentation; in other areas (insular and infralimbic cortices) these changes took place only if the odor cue has been ingested. Associated to the analysis of transient oscillatory synchronizations between these different structures, these results allowed us to better understand how a stimulus could be represented in memory by a cerebral network depending on the way the animal had experienced it.

Les antipsychotiques sont administrés chroniquement pour prévenir de nouveaux épisodes psychotiques dans la schizophrénie. Ces médicaments diminuent l’activité des récepteurs dopaminergiques de type 2. Diminuer chroniquement la transmission dopaminergique induit des compensations pouvant mener à une sensibilisation du système dopaminergique. Cette sensibilisation pourrait diminuer l’efficacité des antipsychotiques et exacerber la psychose. Chez le rat, la sensibilisation dopaminergique induite par les antipsychotiques augmente les effets psychomoteurs et motivationnels des agonistes dopaminergiques. Le premier objectif de la présente thèse était de caractériser les substrats neuronaux régulant l’expression de la sensibilisation dopaminergique évoquée par les antipsychotiques. Ceci est important afin d’améliorer le traitement à long terme de la schizophrénie. Pour ce faire, des rats ont reçu un traitement cliniquement pertinent à l’antipsychotique halopéridol. Ce traitement sensibilise aux effets psychomoteurs de l’agoniste dopaminergique d-amphétamine. Cet indice comportemental de sensibilisation dopaminergique a été utilisé pour déterminer les contributions spécifiques du système dopaminergique et l’implication des effets centraux de la d-amphétamine. Puisqu’il y a une relation étroite entre le stress et l’activité dopaminergique, les réponses liées au stress ont également été mesurées. Ceci est important, puisque le stress exacerbe la psychose. La présente thèse démontre que les récepteurs dopaminergiques régulent de manière distincte la sensibilisation dopaminergique. En effet, la transmission via les récepteurs de type 2 exacerbe cette sensibilisation, alors que la transmission via les récepteurs de type 1 la tempère. Également, la présente thèse suggère que des processus périphériques sont nécessaires à l’expression de la sensibilisation dopaminergique. De plus, la sensibilisation pourrait augmenter les réponses au stress. En effet, cette sensibilisation est renversée lorsque la synthèse de l’hormone de stress corticostérone est inhibée, en plus d’être associée à certains comportements suggérant un stress augmenté. Chez le rat, la sensibilisation dopaminergique évoquée par les antipsychotiques potentialise également les effets motivationnels des stimuli conditionnés prédisant des récompenses. Lorsque ces stimuli acquièrent trop de valeur motivationnelle, ils peuvent motiver des comportements pathologiques. Ainsi, une potentialisation de la valeur motivationnelle des stimuli conditionnés provoquée par les antipsychotiques pourrait avoir des implications importantes dans des processus motivationnels anormaux dans la schizophrénie, tels que la psychose et la forte prévalence de toxicomanie. Ainsi, le deuxième objectif de la présente thèse était d’étudier les mécanismes neurobiologiques régulant les effets comportementaux des stimuli conditionnés, particulièrement le rôle du noyau basolatéral de l’amygdale. Ici, le rôle de ce noyau a été étudié chez des animaux non traités aux antipsychotiques, puisque sa contribution reste incomprise. Ce travail pourrait révéler des mécanismes neurobiologiques potentiellement impliqués dans la sensibilisation dopaminergique évoquée par les antipsychotiques. La présente thèse démontre que l’activation optogénétique de l’amygdale basolatérale potentialise les effets comportementaux des stimuli conditionnés, en augmentant leur valeur motivationnelle et leur capacité à guider le comportement vers des récompenses imminentes. Ainsi, une activité excessive de l’amygdale basolatérale pourrait attribuer trop de pouvoir aux stimuli conditionnés, et ceci pourrait jouer un rôle dans l’état motivationnel anormal provoqué par les antipsychotiques. La présente thèse identifie de nouveaux mécanismes par lesquels les antipsychotiques et les stimuli conditionnés favorisent des réponses pathologiques. / Schizophrenia requires long-term antipsychotic treatment to prevent psychosis relapse. Antipsychotic drugs temper psychotic symptoms by reducing dopamine D2 receptor-mediated signalling. Chronically decreasing dopamine transmission produces neuronal compensation leading to supersensitivity to dopamine stimulation. In patients, this dopamine supersensitivity would compromise antipsychotic efficacy and exacerbate psychotic symptoms. In laboratory animals, antipsychotic-evoked dopamine supersensitivity enhances the psychomotor and reward-enhancing effects of dopamine agonists. The first objective of the present thesis was to characterize the biological substrates mediating the expression of antipsychotic-evoked dopamine supersensitivity, a necessary work for developing better long-term treatment strategies. To do so, rats were chronically exposed to a clinically relevant antipsychotic treatment regimen, using the drug haloperidol. Haloperidol produces dopamine supersensitivity, as indicated by an exaggerated psychomotor response to the dopamine agonist d-amphetamine. This behavioural index of supersensitivity was used to examine the specific contributions of the dopamine system and the central effects of d-amphetamine. Given that there is a close relationship between stress and dopamine activity, it was also determined whether antipsychotic-evoked dopamine supersensitivity alters stress-like responses. This is important to consider because stress is a contributing factor to psychosis relapse. The present thesis first reveals that D1- and D2-mediated transmissions contribute distinctively to the expression of antipsychotic-evoked dopamine supersensitivity, with D2 transmission promoting this supersensitivity and D1 transmission tempering it. The present thesis also provides evidence that peripheral processes play a necessary role in dopamine supersensitivity. Additionally, antipsychotic-evoked dopamine supersensitivity could potentiate stress-like responses. Indeed, the expression of supersensitivity is reversed by inhibition of the synthesis of the stress hormone corticosterone and is linked with some signs of heightened stress-related behaviours. In rats, antipsychotic-evoked dopamine supersensitivity potentiates the incentive motivational effects of reward-predictive conditioned stimuli. When these stimuli acquire too much motivational value, they motivate maladaptive responses. Hence, the increased motivational value of conditioned stimuli elicited by antipsychotic exposure could be involved in impaired motivational processes found in schizophrenia, such as psychosis and the greater vulnerability to drug addiction. Thereby, the last goal of the present thesis was to investigate the neurobiological substrates mediating the behavioural effects of reward-predictive stimuli, with a special focus on the role of the basolateral nucleus of the amygdala. This was investigated in antipsychotic-naïve rats because there are important caveats in our current understanding of the functional role of the basolateral amygdala. Such investigation could give novel insights on the neurobiological effects of antipsychotic-evoked dopamine supersensitivity. Here it is shown that optogenetic stimulation of basolateral amygdala neurons potentiates the behavioural effects of conditioned stimuli, by increasing their motivational value and their ability to guide behaviour toward impending rewards. The implication for this is that excessive activity in the basolateral amygdala could attribute too much motivational power to conditioned stimuli, and this could be involved in the abnormal motivational state produced by antipsychotic drugs. Taken together, the present thesis provides novel mechanisms by which antipsychotic drugs and reward-predictive stimuli promote maladaptive responses.