Submitted by PPG Pediatria e Sa?de da Crian?a (pediatria-pg@pucrs.br) on 2018-05-17T17:25:42Z No. of bitstreams: 1 TESE Thiago Viola Final.pdf: 3221820 bytes, checksum: 98e6a1c6936e1a12973e6fe2d7d12ce5 (MD5) / Approved for entry into archive by Caroline Xavier (caroline.xavier@pucrs.br) on 2018-05-30T16:45:08Z (GMT) No. of bitstreams: 1 TESE Thiago Viola Final.pdf: 3221820 bytes, checksum: 98e6a1c6936e1a12973e6fe2d7d12ce5 (MD5) / Made available in DSpace on 2018-05-30T16:49:19Z (GMT). No. of bitstreams: 1 TESE Thiago Viola Final.pdf: 3221820 bytes, checksum: 98e6a1c6936e1a12973e6fe2d7d12ce5 (MD5) Previous issue date: 2018-03-12 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / Introduction: Child development in adverse environments and conditions, such as with the lack of economic resources or with parental care deprivation, is considered a major risk factor for neurological and psychiatric diseases. Altered cognitive processing is thought to mediate this relationship, however, the neurobiological mechanisms underlying the effects of early adverse experiences on cognition have not yet been fully revealed. Evidence indicates that dopaminergic neurotransmission and the corticotrophinergic system have important functions in the neurobiology of decision-making and risk assessment, which are cognitive processes associated with the functionality of the cerebral cortex. Similarly, working memory is another cognitive domain that underlies cortical activity, and some studies indicate that alterations in neuroimmunologic signaling may contribute to the decline of these higher order cognitive functions. Objectives: To investigate the effects of impoverished housing conditions during early life on risk assessment processing and its associated cortical neurobiological and epigenetic mechanisms in C57BL/6 adolescent mice. In addition, we investigated the effects maternal care deprivation during early life, and the effects of systemic activation of the toll-type receptor (TLR)-3 on working memory performance, and its associated cortical neurobiological mechanisms in male BALB/c mice. Methods: Two studies with rodent experimental models were proposed. The first study used a model of impoverished housing from the postnatal day (P) 2 to P9. During adolescence, risk assessment was investigated using a behavioral paradigm that explores the conflict between two biologically relevant stimuli: the motivation to consume a sweet and highly palatable solution while being threatened by predatory olfactory cues. The expression of dopaminergic (Drd1, Drd2) and corticotrophinergic (Cfr, Crfr1) genes in the medial prefrontal cortex (mPFC) were investigated by real-time PCR. The accumulation of histone marks (H3K9me3, H3R2me2s) were assessed at the promoter region of genes associated with behavioral outcomes. In addition, plasma corticosterone levels were assessed by ELISA. In the second study, a rodent model of maternal care deprivation from P2 to P15 was applied. During adolescence, animals were injected with a TLR-3 agonist, which is a viral receptor implicated with inflammatory signaling, and then tested in a working memory task. The expression of pro-inflammatory genes (Nfkb1, Il6 and Tnf-?) and the receptor itself (Tlr3), were performed in the mPFC by real-time PCR. Results: In the first study, we found increased anxiety-like behavior, increased HPA axis response to stress and impaired RA processing in female adolescent mice, with no effect in males. These sex-specific effects were associated with increased Crfr1 mRNA expression in the medial prefrontal cortex (mPFC), which correlated with an increase in the occupancy of the histone mark H3R2me2s, a histone modification known to be involved in transcriptional activation and epigenetic priming, within the promoter of the Crfr1 gene. In the second study, we found that systemic administration of a TLR-3 agonist can modulate and exacerbate early life stress induced working memory impairments, and that higher gene expression levels of Nfkb1 in the mPFC was associated a lower working memory performance. Conclusions: The findings of the first study indicated a deleterious effect of impoverished housing exposure on risk assessment processing in females, which could be detrimental for cognitive performance in potentially dangerous situations, and suggest that the epigenetic priming of the Crfr1 gene may represent a critical factor mediating the relationship between early life stress and altered cognitive processing later in life in females. Finally, the findings of the second study demonstrated that the systemic activation of TLR-3 can induce working memory impairments, revealing an important mediating role of the neuroinflammatory signalling in the cerebral cortex associated with the cognitive changes resulting from maternal care deprivation exposure during early in life. / Introdu??o: O desenvolvimento infantil em ambientes e condi??es adversas, como frente a escassez de recursos econ?micos ou de cuidado parental, ? considerado fator de risco para doen?as neurol?gicas e psiqui?tricas. Altera??es em processos cognitivos parecem mediar esta rela??o, contudo, os mecanismos neurobiol?gicos adjacentes aos efeitos de experi?ncias adversas precoces sobre a cogni??o ainda n?o foram completamente revelados. Evid?ncias apontam que a neurotransmiss?o dopamin?rgica e o sistema corticotrofin?rgico possuem importantes fun??es na neurobiologia da tomada de decis?o e avalia??o do risco, que s?o processos cognitivos associados a funcionalidade do c?rtex cerebral. Similarmente, a mem?ria de trabalho ? outro dom?nio cognitivo que envolve atividade cortical, e alguns estudos apontam que altera??es na sinaliza??o neuroimunol?gica podem contribuir para o decl?nio destas fun??es cognitivas superiores. Objetivos: Investigar o efeito da exposi??o a moradia empobrecida na inf?ncia sobre o processamento cognitivo de avalia??o do risco e mecanismos neurobiol?gicos e epigen?ticos corticais associados em camundongos adolescentes da linhagem C57BL/6. Al?m disso, investigar o efeito da priva??o do cuidado materno na inf?ncia e da ativa??o sist?mica do receptor do tipo toll (TLR)-3 sobre a mem?ria de trabalho e mecanismos neurobiol?gicos corticais associados em camundongos machos adolescentes da linhagem BALB/c. M?todos: Foram propostos dois estudos com modelos experimentais murinos. O primeiro estudo utilizou um modelo de moradia empobrecida do dia p?s-natal (P) 2 ao P9. Quando os animais encontravam-se no per?odo da adolesc?ncia, o processamento de avalia??o do risco foi investigado por uma tarefa que explora um conflito entre dois est?mulos biologicamente fundamentais na vida de um roedor, a motiva??o de consumir uma solu??o doce e altamente palat?vel (leite condensado) tendo que se expor a pistas olfativas de um predador natural, o coiote. Os n?veis de express?o de genes dopamin?rgicos (Drd1, Drd2) e corticotrofin?rgicos (Cfr, Crfr1) no c?rtex medial pr?-frontal (mPFC) foram investigados por PCR em tempo real. Os n?veis de altera??es de histonas (H3K9me3, H3R2me2s) foram avaliados na regi?o promotora de genes associados aos desfechos comportamentais. Adicionalmente, os n?veis de corticosterona plasm?tica foram avaliados por ELISA. No segundo estudo, o modelo de adversidade utilizado foi o de priva??o do cuidado materno do P2 ao P15. Similarmente, quando os animais encontravam-se no per?odo da adolesc?ncia, ocorreu a administra??o sist?mica de um agonista de TLR-3, um receptor viral relacionado a sinaliza??o inflamat?ria, e posteriormente os animais foram testados em uma tarefa de mem?ria de trabalho. Os n?veis de express?o g?nica de genes pr?-inflamat?rios (Nfkb1, Il6 e Tnf-?) e do pr?prio receptor (Tlr3), foram avaliados no mPFC por PCR em tempo real. Resultados: no primeiro estudo, observou-se um aumento de comportamentos do tipo ansioso, maior responsividade do eixo Hipot?lamo-Pituit?ria-Adrenal (HPA) e uma diminui??o do processamento de avalia??o do risco nas f?meas expostas a moradia empobrecida, ao passo que n?o ocorreram altera??es nos animais machos. A diminui??o de avalia??o do risco foi associada a um aumento na express?o de Crfr1 no mPFC, o que se correlacionou com um aumento dos n?veis de H3R2me2s na regi?o promotora deste gene. No segundo estudo, observou-se que a ativa??o sist?mica de TLR-3 exacerbou os preju?zos de mem?ria de trabalho decorrentes da exposi??o a priva??o do cuidado materno, e este efeito correlacionou-se aos n?veis de express?o de Nfkb1 no mPFC. Conclus?es: os achados do estudo 1 indicam um efeito delet?rio da exposi??o a moradia prec?ria na inf?ncia sobre o processamento de avalia??o do risco em f?meas, revelando um preju?zo espec?fico referente ao engajamento cognitivo frente a situa??es potencialmente perigosas. Al?m disso, evidenciou-se um efeito a n?vel epigen?tico de regula??o da express?o cortical de Crfr1, indicando um importante papel deste gene sobre a rela??o entre pobreza na inf?ncia e altera??es cognitivas em f?meas adolescentes. Por fim, os achados do estudo 2 demonstraram que a ativa??o sist?mica do TLR-3 pode exacerbar os preju?zos de mem?ria de trabalho induzidos pelo estresse precoce, revelando um papel mediador da sinaliza??o neuroinflamat?ria no c?rtex cerebral relacionada as altera??es cognitivas decorrentes da exposi??o a priva??o do cuidado materno.

Diversos estudos demonstram que o estresse infantil, incluindo situações de perda dos pais, negligência e abusos, representa um forte fator de risco para o desenvolvimento de transtornos de ansiedade, sendo de especial interesse para este trabalho, o transtorno do pânico. Modelos de estresse neonatal em animais de laboratório, que se baseiam na ruptura da relação mãe-filhote, como a separação materna e a privação materna, têm sido amplamente utilizados para avaliar as consequências desse estressor sobre a expressão de comportamentos defensivos associados à ansiedade na vida adulta. No entanto, pouco se sabe sobre seus efeitos em modelos animais de ataques de pânico, mais especificamente aqueles que associam esta condição emocional à resposta defensiva de fuga em animais. Diante disso, o objetivo inicial do presente trabalho foi o de estender as investigações dos efeitos do estresse neonatal sobre o comportamento de fuga de ratos adultos (após 60 dias de nascimento) observado no labirinto em T elevado (LTE), pela estimulação elétrica da substância cinzenta periaquedutal (SCPD) e durante a exposição a um ambiente em hipóxia (7% O2). Para efeitos comparativos, esses animais também foram testados em modelos animais associados à ansiedade generalizada e a depressão. Observamos que ratos Wistar submetidos à separação materna (3h/dia, do 2º ao 21º dia pós-nascimento) não diferiram de animais controles nos parâmetros comportamentais analisados nos modelos de pânico (fuga no LTE e pela estimulação elétrica da SCPD), nos de ansiedade (resposta de esquiva no LTE e o beber punido no teste de conflito de Vogel) ou no de depressão (tempo gasto em imobilidade no teste do nado forçado). Já em ratos privados da mãe (por 24h no 11º dia pós- nascimento), embora este estressor não tenha alterada a resposta de fuga no LTE, ele aumentou a expressão deste comportamento durante a exposição à hipóxia, sugestivo de um efeito panicogênico. Ainda empregando a privação materna, observamos que a administração intraperitoneal de um inibidor da síntese de serotonina, a pclorofenilalanina metil éster (p-CPA - 100mg/Kg/dia, por 4 dias antes dos testes comportamentais) facilitou a expressão do comportamento de fuga durante o teste da hipóxia nos animais controle, de maneira semelhante ao efeito obtido somente com a privação materna. Porém este tratamento não potencializou a fuga promovida pela privação materna. Já os níveis plasmáticos de corticosterona foram aumentados pela exposição à hipóxia, independentemente dos animais terem sido previamente privados da mãe ou terem recebido o pCPA antes do teste. Por fim, também observamos, através de uma análise por Western Blotting, que nem a privação materna ou a exposição à hipóxia altera a concentração de receptores serotonérgicos do tipo 5-HT1A na SCPD ou na amígdala. Em suma, nossos resultados mostram que a privação materna promove uma facilitação da resposta de fuga na hipóxia, sugerindo uma relação entre esse estresse neonatal e o desencadeamento de ataques de pânico de um subtipo específico, o pânico respiratório. Contudo, no que diz respeito ao envolvimento da neurotransmissão serotonérgica, mais estudos são necessários para entender sua participação nessa resposta. / Early life stress (ELS), including parental loss due to death, neglect or abuse, represents a major risk factor for the late development of psychiatric disorders, such as anxiety disorders. Animal models of ELS that are based on the disruption of mother-infant relationship, such as the repeated maternal separation or maternal deprivation, have been extensively used for the investigation of the longterm effects of these stressors on the expression of defensive behaviors associated with anxiety. However, little is known about their effects on animal models of panic attacks, more specifically in those that associate this emotional condition with escape behavior in animals. Therefore, the aim of the present study was to extend the investigation on the long-term consequences of neonatal stress on the escape response of adult rats (60 days after birth) evoked by the elevated T maze (ETM), electrical stimulation of the dorsal periaqueductal gray (DPAG) or hypoxia (7% O2). For comparative reasons, these animals were also tested in animal models of anxiety and depression. The results showed that the repeated maternal separation of male Wistar (3 hours/day from day 2 to 21 after birth) did not affect the behavioral indexes measured in the panic (escape in the ETM or after DPAG electrical stimulation), anxiety (ETM inhibitory avoidance or punished licking in the Vogel conflict test) or depression (time in immobility in the forced swimming test) models. On the other hand, rats submitted to maternal deprivation (24 hs in the 11th day after birth), although not differing from the control animals on escape expression in the ETM, showed a pronounced escape response during hypoxia, indicating a panicogenic-like response. Also, using this maternal deprivation protocol, we observed that systemic administration of a 5-HT synthesis inhibitor, p-chlrophenilalanine metylester (p-CPA - 100mg/Kg/day, for 4 days before the behavioral tests), facilitated escape expression during hypoxia in non-deprived animals to a level observed in non-pharmacologically treated deprived animals. We also observed that plasma corticosterone levels were increased 30 minutes after hypoxia exposure, independently of the previous condition of the animals (deprivation or drug treatment). Finally, we observed that the number of 5-HT1A receptors in the DPAG or amygdala, measured by Western Blotting, was not affect by previous maternal deprivation or exposure to hypoxia. Taken together, our results show that a single maternal deprivation episode facilitates the expression of escape behavior during hypoxia, suggesting a relationship between this ELS with the observation of a specific subtype of panic attack, the respiratory panic. Further studies are required in order to clarify the 5- HT involvement on these responses.

A infância e a adolescência são períodos sensíveis de maturação neuronal, caracterizados por alta plasticidade de circuitos encefálicos em desenvolvimento, como é o caso do sistema mesolímbico dopaminérgico. Experiências estressantes neste período, como o isolamento social (IS), podem produzir neuroadaptações nesses circuitos e aumentar a vulnerabilidade ao consumo de drogas e de alimentos palatáveis ao longo da vida. Tendo em vista que extensa literatura analisa longos períodos de isolamento social, que não são modelos adequados para o estresse por isolamento que ocorre em sociedades humanas, o objetivo do presente estudo foi investigar os efeitos de uma exposição curta ao isolamento social durante o período pré-púbere sobre o sistema mesolímbico dopaminérgico e a susceptibilidade para o abuso de drogas e para o consumo compulsivo de alimento palatável em ratas Wistar fêmeas, na idade adulta. Também foi objetivo avaliar o papel da exposição crônica a uma dieta rica em sacarose (DRS) sobre estas variáveis. Como resultados, foi observado que o IS aumentou a resposta locomotora a um desafio com anfetamina, bem como aumentou, no estriado dorsal, o imunoconteúdo do transportador de dopamina, da enzima tirosina hidroxilase e diminuiu os níveis do receptor D2 de dopamina (D2R); além disso, os animais submetidos ao IS na pré-puberdade apresentaram aumento nos parâmetros relacionados ao estresse oxidativo após o desafio. De modo interessante, a exposição a DRS preveniu os efeitos do IS sobre a resposta locomotora, mas não afetou os parâmetros dopaminérgicos. O IS também diminuiu o imunoconteúdo basal de D2R no núcleo accumbens (NAc) e estimulou o consumo do tipo-compulsivo de alimento doce (Froot Loops®). A DRS não interferiu nestes parâmetros. Observamos também que o IS não alterou os níveis basais de corticosterona plasmática, enquanto que a DRS diminuiu tais níveis. Os registros das correntes excitatórias pós-sinápticas (CEPS) espontâneas indicaram, como resultado preliminar, que a DRS reduziu o tempo de subida das CEPS, indicando uma resposta glutamatérgica fugaz. Os achados deste estudo demonstram pela primeira vez que um período curto de IS em uma fase crítica do desenvolvimento é capaz de programar o sistema mesolímbico dopaminérgico de forma a aumentar a susceptibilidade tanto ao uso de drogas quanto ao consumo do tipo-aditivo de alimento doce. Esses efeitos podem ser em parte explicados pela redução dos níveis de D2R basal no NAc e pela maior estimulação do sistema dopaminérgico no estriado frente a um desafio com anfetamina. Os achados desta tese sugerem que experiências estressantes, como o isolamento social, durante um período crítico do desenvolvimento é capaz de programar o sistema de recompensa encefálico de forma permanente e aumentar a susceptibilidade a comportamentos aditivos na vida adulta. Identificar fatores preditores de propensão a esse tipo de comportamento é importante para prevenir o desenvolvimento de dependência de drogas e/ou de distúrbios alimentares, além de possibilitar a identificação de alvos terapêuticos e o desenvolvimento de estratégias de tratamento para estes distúrbios. / Childhood and adolescence are sensitive periods of neuronal maturation, characterized by high plasticity of developing brain circuits, such as the mesolimbic dopaminergic system. Stressful experiences in these periods, such as social isolation (SI), can produce changes in these circuits and increase vulnerability to drug addiction and eating disorders throughout life. Considering that most of literature analyze long periods of social isolation, that are not good models for social stress in human societies, the objective of this study was to investigate the effects of a short post-weaning social isolation on mesolimbic dopaminergic system and the susceptibility to drug and food addiction in female Wistar rats in adulthood. Moreover, we also aimed to evaluate the role of a chronic high sugar diet (HSD) on these variables. It was observed that IS increased the locomotor response to a challenge with amphetamine (AMPH), as well as increased the immunocontent of dopamine transporter, the enzyme tyrosine hydroxylase, decreased the D2 dopamine receptor (D2R) and increased the parameters related to oxidative stress in dorsal striatum after the challenge. Interestingly, exposure to DRS prevented the effects of SI on locomotor response, but did not affect dopaminergic parameters. IS also decreased the basal immunocontent of D2R in the nucleus accumbens (NAc), and stimulated binge eating of high sweet food (Froot Loops®). HSD did not interfere with these parameters. We also observed that SI did not alter plasma corticosterone baseline levels after IS, whereas HSD induced a decrease in these levels. Excitatory postsynaptic currents (EPSC) indicated, as a preliminary result, that the exposure to a HSD reduced the rise time, indicating a more fleeting glutamatergic response. The findings of this study demonstrate for the first time that a short period of SI at a critical period of development is able to programme the mesolimbic dopaminergic system in order to increase susceptibility to both drug and food addiction. These results are possibly due, at least in part, to low basal levels of D2R in NAc and the higher stimulation of the dopaminergic system in striatum after a challenge with AMPH. The findings of this thesis suggest that stressful experiences such as social isolation during a critical period of development are able to permanently program the brain reward system and increase the susceptibility to additive behaviors in adult life. Identifying predisposing factors to this type of behavior is extremely important to prevent the development of drug addiction and/or eating disorders, to identify therapeutic targets and to enable the development of treatment strategies for these disorders.

Diversos estudos demonstram que o estresse infantil, incluindo situações de perda dos pais, negligência e abusos, representa um forte fator de risco para o desenvolvimento de transtornos de ansiedade, sendo de especial interesse para este trabalho, o transtorno do pânico. Modelos de estresse neonatal em animais de laboratório, que se baseiam na ruptura da relação mãe-filhote, como a separação materna e a privação materna, têm sido amplamente utilizados para avaliar as consequências desse estressor sobre a expressão de comportamentos defensivos associados à ansiedade na vida adulta. No entanto, pouco se sabe sobre seus efeitos em modelos animais de ataques de pânico, mais especificamente aqueles que associam esta condição emocional à resposta defensiva de fuga em animais. Diante disso, o objetivo inicial do presente trabalho foi o de estender as investigações dos efeitos do estresse neonatal sobre o comportamento de fuga de ratos adultos (após 60 dias de nascimento) observado no labirinto em T elevado (LTE), pela estimulação elétrica da substância cinzenta periaquedutal (SCPD) e durante a exposição a um ambiente em hipóxia (7% O2). Para efeitos comparativos, esses animais também foram testados em modelos animais associados à ansiedade generalizada e a depressão. Observamos que ratos Wistar submetidos à separação materna (3h/dia, do 2º ao 21º dia pós-nascimento) não diferiram de animais controles nos parâmetros comportamentais analisados nos modelos de pânico (fuga no LTE e pela estimulação elétrica da SCPD), nos de ansiedade (resposta de esquiva no LTE e o beber punido no teste de conflito de Vogel) ou no de depressão (tempo gasto em imobilidade no teste do nado forçado). Já em ratos privados da mãe (por 24h no 11º dia pós- nascimento), embora este estressor não tenha alterada a resposta de fuga no LTE, ele aumentou a expressão deste comportamento durante a exposição à hipóxia, sugestivo de um efeito panicogênico. Ainda empregando a privação materna, observamos que a administração intraperitoneal de um inibidor da síntese de serotonina, a pclorofenilalanina metil éster (p-CPA - 100mg/Kg/dia, por 4 dias antes dos testes comportamentais) facilitou a expressão do comportamento de fuga durante o teste da hipóxia nos animais controle, de maneira semelhante ao efeito obtido somente com a privação materna. Porém este tratamento não potencializou a fuga promovida pela privação materna. Já os níveis plasmáticos de corticosterona foram aumentados pela exposição à hipóxia, independentemente dos animais terem sido previamente privados da mãe ou terem recebido o pCPA antes do teste. Por fim, também observamos, através de uma análise por Western Blotting, que nem a privação materna ou a exposição à hipóxia altera a concentração de receptores serotonérgicos do tipo 5-HT1A na SCPD ou na amígdala. Em suma, nossos resultados mostram que a privação materna promove uma facilitação da resposta de fuga na hipóxia, sugerindo uma relação entre esse estresse neonatal e o desencadeamento de ataques de pânico de um subtipo específico, o pânico respiratório. Contudo, no que diz respeito ao envolvimento da neurotransmissão serotonérgica, mais estudos são necessários para entender sua participação nessa resposta. / Early life stress (ELS), including parental loss due to death, neglect or abuse, represents a major risk factor for the late development of psychiatric disorders, such as anxiety disorders. Animal models of ELS that are based on the disruption of mother-infant relationship, such as the repeated maternal separation or maternal deprivation, have been extensively used for the investigation of the longterm effects of these stressors on the expression of defensive behaviors associated with anxiety. However, little is known about their effects on animal models of panic attacks, more specifically in those that associate this emotional condition with escape behavior in animals. Therefore, the aim of the present study was to extend the investigation on the long-term consequences of neonatal stress on the escape response of adult rats (60 days after birth) evoked by the elevated T maze (ETM), electrical stimulation of the dorsal periaqueductal gray (DPAG) or hypoxia (7% O2). For comparative reasons, these animals were also tested in animal models of anxiety and depression. The results showed that the repeated maternal separation of male Wistar (3 hours/day from day 2 to 21 after birth) did not affect the behavioral indexes measured in the panic (escape in the ETM or after DPAG electrical stimulation), anxiety (ETM inhibitory avoidance or punished licking in the Vogel conflict test) or depression (time in immobility in the forced swimming test) models. On the other hand, rats submitted to maternal deprivation (24 hs in the 11th day after birth), although not differing from the control animals on escape expression in the ETM, showed a pronounced escape response during hypoxia, indicating a panicogenic-like response. Also, using this maternal deprivation protocol, we observed that systemic administration of a 5-HT synthesis inhibitor, p-chlrophenilalanine metylester (p-CPA - 100mg/Kg/day, for 4 days before the behavioral tests), facilitated escape expression during hypoxia in non-deprived animals to a level observed in non-pharmacologically treated deprived animals. We also observed that plasma corticosterone levels were increased 30 minutes after hypoxia exposure, independently of the previous condition of the animals (deprivation or drug treatment). Finally, we observed that the number of 5-HT1A receptors in the DPAG or amygdala, measured by Western Blotting, was not affect by previous maternal deprivation or exposure to hypoxia. Taken together, our results show that a single maternal deprivation episode facilitates the expression of escape behavior during hypoxia, suggesting a relationship between this ELS with the observation of a specific subtype of panic attack, the respiratory panic. Further studies are required in order to clarify the 5- HT involvement on these responses.

A infância e a adolescência são períodos sensíveis de maturação neuronal, caracterizados por alta plasticidade de circuitos encefálicos em desenvolvimento, como é o caso do sistema mesolímbico dopaminérgico. Experiências estressantes neste período, como o isolamento social (IS), podem produzir neuroadaptações nesses circuitos e aumentar a vulnerabilidade ao consumo de drogas e de alimentos palatáveis ao longo da vida. Tendo em vista que extensa literatura analisa longos períodos de isolamento social, que não são modelos adequados para o estresse por isolamento que ocorre em sociedades humanas, o objetivo do presente estudo foi investigar os efeitos de uma exposição curta ao isolamento social durante o período pré-púbere sobre o sistema mesolímbico dopaminérgico e a susceptibilidade para o abuso de drogas e para o consumo compulsivo de alimento palatável em ratas Wistar fêmeas, na idade adulta. Também foi objetivo avaliar o papel da exposição crônica a uma dieta rica em sacarose (DRS) sobre estas variáveis. Como resultados, foi observado que o IS aumentou a resposta locomotora a um desafio com anfetamina, bem como aumentou, no estriado dorsal, o imunoconteúdo do transportador de dopamina, da enzima tirosina hidroxilase e diminuiu os níveis do receptor D2 de dopamina (D2R); além disso, os animais submetidos ao IS na pré-puberdade apresentaram aumento nos parâmetros relacionados ao estresse oxidativo após o desafio. De modo interessante, a exposição a DRS preveniu os efeitos do IS sobre a resposta locomotora, mas não afetou os parâmetros dopaminérgicos. O IS também diminuiu o imunoconteúdo basal de D2R no núcleo accumbens (NAc) e estimulou o consumo do tipo-compulsivo de alimento doce (Froot Loops®). A DRS não interferiu nestes parâmetros. Observamos também que o IS não alterou os níveis basais de corticosterona plasmática, enquanto que a DRS diminuiu tais níveis. Os registros das correntes excitatórias pós-sinápticas (CEPS) espontâneas indicaram, como resultado preliminar, que a DRS reduziu o tempo de subida das CEPS, indicando uma resposta glutamatérgica fugaz. Os achados deste estudo demonstram pela primeira vez que um período curto de IS em uma fase crítica do desenvolvimento é capaz de programar o sistema mesolímbico dopaminérgico de forma a aumentar a susceptibilidade tanto ao uso de drogas quanto ao consumo do tipo-aditivo de alimento doce. Esses efeitos podem ser em parte explicados pela redução dos níveis de D2R basal no NAc e pela maior estimulação do sistema dopaminérgico no estriado frente a um desafio com anfetamina. Os achados desta tese sugerem que experiências estressantes, como o isolamento social, durante um período crítico do desenvolvimento é capaz de programar o sistema de recompensa encefálico de forma permanente e aumentar a susceptibilidade a comportamentos aditivos na vida adulta. Identificar fatores preditores de propensão a esse tipo de comportamento é importante para prevenir o desenvolvimento de dependência de drogas e/ou de distúrbios alimentares, além de possibilitar a identificação de alvos terapêuticos e o desenvolvimento de estratégias de tratamento para estes distúrbios. / Childhood and adolescence are sensitive periods of neuronal maturation, characterized by high plasticity of developing brain circuits, such as the mesolimbic dopaminergic system. Stressful experiences in these periods, such as social isolation (SI), can produce changes in these circuits and increase vulnerability to drug addiction and eating disorders throughout life. Considering that most of literature analyze long periods of social isolation, that are not good models for social stress in human societies, the objective of this study was to investigate the effects of a short post-weaning social isolation on mesolimbic dopaminergic system and the susceptibility to drug and food addiction in female Wistar rats in adulthood. Moreover, we also aimed to evaluate the role of a chronic high sugar diet (HSD) on these variables. It was observed that IS increased the locomotor response to a challenge with amphetamine (AMPH), as well as increased the immunocontent of dopamine transporter, the enzyme tyrosine hydroxylase, decreased the D2 dopamine receptor (D2R) and increased the parameters related to oxidative stress in dorsal striatum after the challenge. Interestingly, exposure to DRS prevented the effects of SI on locomotor response, but did not affect dopaminergic parameters. IS also decreased the basal immunocontent of D2R in the nucleus accumbens (NAc), and stimulated binge eating of high sweet food (Froot Loops®). HSD did not interfere with these parameters. We also observed that SI did not alter plasma corticosterone baseline levels after IS, whereas HSD induced a decrease in these levels. Excitatory postsynaptic currents (EPSC) indicated, as a preliminary result, that the exposure to a HSD reduced the rise time, indicating a more fleeting glutamatergic response. The findings of this study demonstrate for the first time that a short period of SI at a critical period of development is able to programme the mesolimbic dopaminergic system in order to increase susceptibility to both drug and food addiction. These results are possibly due, at least in part, to low basal levels of D2R in NAc and the higher stimulation of the dopaminergic system in striatum after a challenge with AMPH. The findings of this thesis suggest that stressful experiences such as social isolation during a critical period of development are able to permanently program the brain reward system and increase the susceptibility to additive behaviors in adult life. Identifying predisposing factors to this type of behavior is extremely important to prevent the development of drug addiction and/or eating disorders, to identify therapeutic targets and to enable the development of treatment strategies for these disorders.

No description available.

A infância e a adolescência são períodos sensíveis de maturação neuronal, caracterizados por alta plasticidade de circuitos encefálicos em desenvolvimento, como é o caso do sistema mesolímbico dopaminérgico. Experiências estressantes neste período, como o isolamento social (IS), podem produzir neuroadaptações nesses circuitos e aumentar a vulnerabilidade ao consumo de drogas e de alimentos palatáveis ao longo da vida. Tendo em vista que extensa literatura analisa longos períodos de isolamento social, que não são modelos adequados para o estresse por isolamento que ocorre em sociedades humanas, o objetivo do presente estudo foi investigar os efeitos de uma exposição curta ao isolamento social durante o período pré-púbere sobre o sistema mesolímbico dopaminérgico e a susceptibilidade para o abuso de drogas e para o consumo compulsivo de alimento palatável em ratas Wistar fêmeas, na idade adulta. Também foi objetivo avaliar o papel da exposição crônica a uma dieta rica em sacarose (DRS) sobre estas variáveis. Como resultados, foi observado que o IS aumentou a resposta locomotora a um desafio com anfetamina, bem como aumentou, no estriado dorsal, o imunoconteúdo do transportador de dopamina, da enzima tirosina hidroxilase e diminuiu os níveis do receptor D2 de dopamina (D2R); além disso, os animais submetidos ao IS na pré-puberdade apresentaram aumento nos parâmetros relacionados ao estresse oxidativo após o desafio. De modo interessante, a exposição a DRS preveniu os efeitos do IS sobre a resposta locomotora, mas não afetou os parâmetros dopaminérgicos. O IS também diminuiu o imunoconteúdo basal de D2R no núcleo accumbens (NAc) e estimulou o consumo do tipo-compulsivo de alimento doce (Froot Loops®). A DRS não interferiu nestes parâmetros. Observamos também que o IS não alterou os níveis basais de corticosterona plasmática, enquanto que a DRS diminuiu tais níveis. Os registros das correntes excitatórias pós-sinápticas (CEPS) espontâneas indicaram, como resultado preliminar, que a DRS reduziu o tempo de subida das CEPS, indicando uma resposta glutamatérgica fugaz. Os achados deste estudo demonstram pela primeira vez que um período curto de IS em uma fase crítica do desenvolvimento é capaz de programar o sistema mesolímbico dopaminérgico de forma a aumentar a susceptibilidade tanto ao uso de drogas quanto ao consumo do tipo-aditivo de alimento doce. Esses efeitos podem ser em parte explicados pela redução dos níveis de D2R basal no NAc e pela maior estimulação do sistema dopaminérgico no estriado frente a um desafio com anfetamina. Os achados desta tese sugerem que experiências estressantes, como o isolamento social, durante um período crítico do desenvolvimento é capaz de programar o sistema de recompensa encefálico de forma permanente e aumentar a susceptibilidade a comportamentos aditivos na vida adulta. Identificar fatores preditores de propensão a esse tipo de comportamento é importante para prevenir o desenvolvimento de dependência de drogas e/ou de distúrbios alimentares, além de possibilitar a identificação de alvos terapêuticos e o desenvolvimento de estratégias de tratamento para estes distúrbios. / Childhood and adolescence are sensitive periods of neuronal maturation, characterized by high plasticity of developing brain circuits, such as the mesolimbic dopaminergic system. Stressful experiences in these periods, such as social isolation (SI), can produce changes in these circuits and increase vulnerability to drug addiction and eating disorders throughout life. Considering that most of literature analyze long periods of social isolation, that are not good models for social stress in human societies, the objective of this study was to investigate the effects of a short post-weaning social isolation on mesolimbic dopaminergic system and the susceptibility to drug and food addiction in female Wistar rats in adulthood. Moreover, we also aimed to evaluate the role of a chronic high sugar diet (HSD) on these variables. It was observed that IS increased the locomotor response to a challenge with amphetamine (AMPH), as well as increased the immunocontent of dopamine transporter, the enzyme tyrosine hydroxylase, decreased the D2 dopamine receptor (D2R) and increased the parameters related to oxidative stress in dorsal striatum after the challenge. Interestingly, exposure to DRS prevented the effects of SI on locomotor response, but did not affect dopaminergic parameters. IS also decreased the basal immunocontent of D2R in the nucleus accumbens (NAc), and stimulated binge eating of high sweet food (Froot Loops®). HSD did not interfere with these parameters. We also observed that SI did not alter plasma corticosterone baseline levels after IS, whereas HSD induced a decrease in these levels. Excitatory postsynaptic currents (EPSC) indicated, as a preliminary result, that the exposure to a HSD reduced the rise time, indicating a more fleeting glutamatergic response. The findings of this study demonstrate for the first time that a short period of SI at a critical period of development is able to programme the mesolimbic dopaminergic system in order to increase susceptibility to both drug and food addiction. These results are possibly due, at least in part, to low basal levels of D2R in NAc and the higher stimulation of the dopaminergic system in striatum after a challenge with AMPH. The findings of this thesis suggest that stressful experiences such as social isolation during a critical period of development are able to permanently program the brain reward system and increase the susceptibility to additive behaviors in adult life. Identifying predisposing factors to this type of behavior is extremely important to prevent the development of drug addiction and/or eating disorders, to identify therapeutic targets and to enable the development of treatment strategies for these disorders.

A plethora of naturally-produced steroid hormones, or artificial homologues of them, are being introduced into the aquatic and terrestrial environments each year. Two examples of these are the natural oestrogen 17-oestradiol (E2) and the oestrogen receptor antagonist, Bisphenol A (BPA), both of which target the ribonucleoprotein telomerase through upregulation of its telomerase reverse transcriptase component, TERT. The main objectives of this study were firstly to isolate and characterize the actual mRNA sequence for the telomerase catalytic subuninit, Tert, in rainbow trout (Oncorhynchus mykiss) (Walbaum, 1792) and European purple sea urchin (Paracentrotus lividus) (Lamarck, 1816), with the aim of developing qPCR assays for the amplification and quantification of Tert. Further objectives were to use these assays in controlled exposure studies to establish whether and to what extent the aforementioned chemicals regulate Tert transcription and by doing so further understand the mechanism of Telomerase gene expression and the extent to which environmental oestrogen can interfere. The initial step of sequence characterization and assay devlopment was successful in the case of rainbow trout where two possible splice variants of Tert mRNA are identified, omTertShort and omTertLong. Two qPCR assays were developed for the relative quantification of both of these splice variants in rainbow trout samples, the latter of these successfully amplifying its target in test samples. In order to demonstrate in vitro and in vivo modulation of telomerase activity and mRNA expression, early life-stages of rainbow trout and purple sea urchin, as well as rainbow trout hepatocytes, were exposed to a range of concentrations of E2 and BPA. Purple sea urchin embryos were exposed to 200, 20 and 2 ng E2/ml for 28 hours until they had reached the stage of pluteus larvaes. Rainbow trout embryos were exposed to 500, 20 and 0.1 ng E2/ml and 600 and 150 ng BPA/ml for 167 days from immediately after fertilization. Rainbow trout hepatocytes were exposed to 20 and 2 ng E2/ml for 48 hours. The results from this study show that telomerase activity as well as TERT mRNA expression can be significantly modulated by exposure to oestrogens and other oestrogenic chemicals. E2 concentrations as low as 20 ng/ml lead to an increase in telomerase activity early-life stages of purple sea urchin and upregulation in the transcription of Tert mRNA in unhatched rainbow trout embryos. BPA induced similar response (600 ng/ml) in hatched rainbow trout alevins larvae. Very high exposures to E2 (500 ng/ml) do however lead to downregulation of Tert mRNA in hatched alevins larvae. Differential regulatory response can be observed between different tissue types of 167 day old fry, with an upregulatory response observed at 0.1 ng E2/ml in liver and muscle tissues, but not in brain. Similarly, brain tissues were observed expressing significantly less mRNA than liver and muscle samples when exposed to BPA (150 ng/ml). It is evident that the previously observed link between environmental oestrogens and telomerase is also present in the two test species examined; purple sea urchin and rainbow trout.

The Atlantic cod (Gadus morhua L.) fishery is of great economic importance to the Faroese economy. There are two separately managed cod stocks around the Faroe Islands, the Faroe Plateau and the Faroe Bank cod. Both have experienced dramatic decreases in size and informed management decisions are vital for both stock viability and exploitation. The stocks are geographically isolated by an 800 m deep channel and water temperatures are on average 1 – 2 ºC higher on the Faroe Bank than on the Faroe Plateau. There are clear phenotypic differences between the stocks; in particular, the markedly higher growth rate for the Faroe Bank cod has caught public and scientific attention. There is continuing debate regarding the relative importance of genetics and environmental contributions to the contrasting phenotypes. Analyses of reproductive parameters (field data and experimental captive spawnings) as well as analyses of microsatellite and single nucleotide polymorphism (SNP) markers were undertaken to better resolve the issue. Field data as well as data from experimental captive spawnings provided evidence of reproductive differences between Faroe Plateau and Faroe Bank cod. Peak spawning occurred earlier on the Faroe Plateau than on the Faroe Bank and this difference in timing of spawning was maintained in captivity. In particular, differences in sizes of eggs (average diameters of 1.40 and 1.30 mm for Faroe Plateau and Faroe Bank cod eggs, respectively) and indirect evidence of greater volumes spawned by the Faroe Bank females suggested stock differences with respect to egg size – egg number trade-off. It was hypothesised that the strategy adopted by cod on the Faroe Bank, with a higher number of smaller eggs, evolved in response to a more hostile environment (bare seabed and higher exposure to predators) experienced by early life stages in this area. Experimental captive spawnings with Faroe Bank cod showed a large interfamily skew in survival rates of cod eggs and fry. Egg size was identified as a useful indicator of survival rates in the egg stage, but egg survival rates could not be used to predict viability in later developmental stages, thus highlighting the importance of employing some sort of genetic monitoring of cod fry to ensure sufficient family representation in the progeny. While no tank effect was evident concerning fry survival, a significant tank effect was identified concerning body sizes of fry. Microsatellite data were analysed using large sample sizes of Faroe Plateau and Faroe Bank cod with the Faroe Plateau divided into two locations, Faroe Plateau North-East and Faroe Plateau West (cod from each of the two were known to belong to separate spawning grounds). Two Norwegian coastal cod samples were included as outlier populations. While no genetic differentiation was detected between the two Faroe Plateau locations, these analyses revealed a detectable, albeit relatively modest, degree of genetic differentiation between cod from the Faroe Plateau and the Faroe Bank (FST = 0.0014 and 0.0018; DJost_EST = 0.0027 and 0.0048; P < 0.0001 and P < 0.001 for the Faroe Plateau North-East – Faroe Bank and the Faroe Plateau West – Faroe Bank comparisons). These values were several times smaller than those between Faroese and Norwegian coastal cod (pairwise FST and DJost_EST values in the range of 0.0061 – 0.0137 and 0.0158 – 0.0386, respectively). Despite recent reductions in census population sizes for Faroe Plateau and, particularly, Faroe Bank cod, genetic diversity estimates were comparable to the ones observed for Norwegian coastal cod and there was no evidence of significant genetic bottlenecks. Lastly, data for one of the markers (Gmo132) indicated genotype-dependent vertical distribution of cod (as investigated for Faroe Plateau North-East cod). Contrary to some previously published studies, analysis of SNPs of two candidate genes for adaptive divergence, the hemoglobin gene Hb-ß1 and the transferrin gene Tf1, failed to detect differentiation between samples of Faroe Plateau and Faroe Bank cod analysed in this thesis. Of 3533 novel SNPs simultaneously discovered and genotyped by restriction-site associated DNA (RAD) sequencing, 58 showed evidence of genetic differentiation between Faroe Plateau North-East and Faroe Bank cod (P < 0.05). No single locus was fixed for different alleles between Faroe Plateau and Faroe Bank cod. A set of eight informative SNPs (FST values between Faroe Plateau and Faroe Bank samples > 0.25; P < 0.0005) were selected for validation in larger samples, that included cod from both Faroe Plateau areas and the Faroe Bank as well as Norwegian coastal and White Sea cod. Six out of the eight loci amplified successfully with a PCR-based method and there was 100 % concordance between genotypes of individuals screened by both techniques. Due to ascertainment bias, the SNPs should only be applied with caution in a broader geographical context. Nonetheless, these SNPs did confirm the genetic substructure suggested for Faroese cod by microsatellite analyses. While no genetic differentiation was evident between the two Faroe Plateau locations, significant genetic differentiation was evident between Faroe Plateau and Faroe Bank cod at five of the SNPs (FST values in the range of 0.0383 – 0.1914). This panel of five SNPs could confidently be used to trace groups of Faroe Plateau and Faroe Bank cod to their population of origin. In conclusion, multiple lines of evidence demonstrate that Faroe Plateau and Faroe Bank cod are truly two genetically distinct populations. While the findings contribute to a broader understanding of the biology and the genetics of Faroe Plateau and Faroe Bank cod, the novel SNPs developed may provide a valuable resource for potential future demands of i.e. genetic stock identification methods.

Trajectoires développementales de l’IMC durant l’enfance: Une étude longitudinale sur 8 ans. Introduction : L’obésité infantile, origine de nombreux problèmes de santé, représente un grand défi en santé publique. Récemment, l’importance d’étudier l’évolution du surpoids durant l’enfance ainsi que les facteurs de risques précoces pour l’obésité a été reconnue. Les trajectoires développementales d’indice de masse corporelle (IMC) chez les jeunes représentent une approche innovatrice qui nous permet de mieux comprendre cette problématique importante. Objectifs: 1) Identifier des trajectoires développementales distinctes de groupes d’enfants selon leur IMC durant l’enfance, et 2) Explorer les facteurs de risques précoces qui prédisent l’appartenance de l’enfant à la trajectoire d’IMC le plus élevé Hypothèses: 1) On s’attend à retrouver un groupe d’enfants qui suit une trajectoire d’IMC élevée durant l’enfance. 2) On s’attend à ce que certaines caractéristiques de la mère (ex : tabac pendant la grossesse et IMC élevé), soient associées à l’appartenance de l’enfant au groupe ayant la trajectoire «IMC élevé ». Méthodes: Estimation des trajectoires développementales d’IMC d’enfants, dans un échantillon populationnel (n=1957) au Québec (ELDEQ). Les IMC ont été calculés à partir de données fournies par les mères des enfants et recueillis chaque année sur une durée de 8 ans. Des données propres à l’enfant sa mère, ainsi que socioéconomiques, ont étés recueillies. Une régression logistique multinomiale a été utilisée pour distinguer les enfants avec un IMC élevé des autres enfants, selon les facteurs de risques précoces. Les programmes PROC TRAJ (extension de SAS), SPSS (version 16), et SAS (version 9.1.3) ont été utilisés pour ces analyses. Résultats: Trois trajectoires d’IMC ont étés identifiées : IMC « bas-stable » (54,5%), IMC « modéré » (41,0%) et IMC « élevé et en hausse » (4,5%). Le groupe « élevé et en hausse » incluait des enfants pour qui l’IMC à 8 ans dépassait la valeur limite pour l’obésité. Les analyses de régression logistique ont révélé que deux facteurs de risques maternels étaient significativement associés avec la trajectoire “en hausse” par rapport aux deux autres groupes : le tabac durant la grossesse et le surpoids maternel. Conclusions: Des risques d’obésité infantile peuvent êtres identifiés dès la grossesse. Des études d’intervention sont requises pour identifier la possibilité de réduire le risque d’obésité chez l’enfant en ciblant le tabac et le surpoids maternelle durant la grossesse. Mots clés: Indice de masse corporelle (IMC), obésité infantile, trajectoires développementales de groupe, facteurs de risque précoce, étude populationnelle, tabac pendant la grossesse, obésité maternelle. / Developmental Trajectories of Body Mass Index in Early Childhood: An 8-Year Longitudinal Study. Introduction: Childhood obesity has become one of the greatest Public Health challenges this century, affecting not only developed nations, but increasingly low- and middle-income countries as well. Estimating developmental trajectories of Body Mass Index (BMI) during early childhood represents an innovative approach towards a better understanding of the development of this health problem. Objective: To identify groups of children with distinct developmental trajectories of Body Mass Index (BMI) between the ages of five months and eight years, and to identify early-life risk factors that distinguish children in an atypically elevated BMI trajectory group. Methods: Group-based developmental trajectories of BMI were estimated from annual maternal assessments (5 months to 8 years) in a large population sample (n=1957). Measures of height and weight, as well as family and child characteristics were obtained yearly from mothers. Multivariate logistic regression was used to distinguish children with elevated BMI from other children, using pre and early post-natal risk factors. Results: Three trajectories of BMI were identified: low-stable BMI (54.5%), moderate BMI (41.0%) and high-rising BMI (4.5%). The high-rising group included children whose BMI, at eight years of age, exceeded the cut-off value for obesity. Multinomial logit regression analyses revealed that two maternal risk factors were significantly associated with the high-rising BMI trajectory group as compared to both the low and moderate groups: smoking during pregnancy and maternal overweight. Conclusions: Antecedents of childhood obesity can be identified during pregnancy. Intervention studies are needed in order to test the possibility that targeting maternal smoking and maternal obesity during pregnancy would reduce the risk of childhood obesity in the offspring. Keywords: Body Mass Index (BMI), child obesity, Group-based developmental trajectories, early life predictors, population-based study, maternal smoking, maternal obesity.