L’addiction aux drogues est une maladie comportementale récidivante caractérisée par une recherche et une prise compulsive de drogues, une perte de contrôle sur la prise malgré les conséquences négatives et l’émergence d'un état émotionnel négatif lors de l’absence de la drogue. L’addiction implique des neuroadaptations cérébrales persistantes. Des études récentes montrent que le cholestérol joue un rôle crucial dans le fonctionnement cérébral en participant à divers processus cellulaires et, en particulier, au contrôle de la neurotransmission. L’objectif de ce travail de thèse consistait à étudier l’implication potentielle du métabolisme du cholestérol dans l’addiction et en particulier si ce métabolisme était affecté par les drogues d’abus. Dans ce travail, nous avons étudié l’expression de gènes codant des protéines impliquées dans le métabolisme du cholestérol cérébral après une consommation volontaire chronique d’alcool par des rats et après des injections aigues ou chroniques de cocaïne. Nous avons analysé l’expression de ces gènes dans des structures cérébrales impliquées dans l’addiction, notamment le cortex préfrontal, le noyau accumbens, l’amygdale et l’hippocampe. Nous avons trouvé que l’exposition à l’alcool et à la cocaïne modifient l’expression des protéines impliquées dans la synthèse, le transport et la dégradation du cholestérol de façon spécifique de la drogue, du traitement (aigu/chronique) et de la région cérébrale étudiée. Dans une deuxième partie de la thèse, nous avons utilisé une approche virale permettant de surexprimer la CYP46A1, l’enzyme de dégradation du cholestérol cérébral dans le cortex préfrontal afin d’évaluer l’impact de cette surexpression sur la recherche de cocaïne dans un modèle de rechute. La surexpression de la CYP46A1dans cette structure n’a eu aucun impact sur la recherche de cocaïne. Des études futures seront nécessaires pour déterminer si l’altération de l’expression de cette enzyme dans d’autres structures, comme par exemple le noyau accumbens, pourrait avoir des effets bénéfiques sur la rechute. L’ensemble de ces travaux montrent que l’exposition aux drogues d’abus modulerait le métabolisme cérébral du cholestérol dans certaines structures cérébrales. Ce projet de thèse ouvre de nouvelles perspectives quant au rôle du métabolisme du cholestérol cérébral dans l’addiction, et il pourrait en résulter de nouvelles thérapeutiques dans le traitement de cette maladie psychiatrique coûteuse. / Drug addiction is a chronic brain disease characterized by drug-seeking and compulsive drug taking, a loss of control over drug taking despite the negative consequences and the emergence of a negative emotional state in the absence of the drug. Addiction involves persistent neuroadaptations at the cerebral level. Recent evidences show that cholesterol plays a crucial role in brain function by participating in various cellular processes in particular in the control of neurotransmission. The aim of this thesis was to investigate the potential role of cholesterol in addiction and in particular a potential dysregulation of cholesterol metabolism in response to drugs of abuse. In this work, we investigated the expression of genes encoding proteins involved in the metabolism of cerebral cholesterol after a chronic voluntary consumption of alcohol from the rats and after acute or chronic exposure to cocaine. We analyzed gene expression in brain structures involved in addiction such as the prefrontal cortex, the nucleus accumbens, the amygdala and the hippocampus. We found that exposure to alcohol and cocaine modifies the expression of proteins involved in the synthesis, the transport and the degradation of cholesterol in drug-specific, treatment- specific (acute / chronic) and region-specific manners. In the second part of the thesis, we used a viral approach to overexpress CYP46A1, the cerebral cholesterol degradation enzyme in the prefrontal cortex, in order to evaluate the impact of this overexpression on cocaine-seeking in a model of relapse. The overexpression of CYP in this structure has no effect on drug-seeking for cocaine. Future studies are needed to determine whether altering cholesterol metabolism in other structures, for example the nucleus accumbens, may have beneficial effects on relapse. Altogether these studies show that exposure to drugs of abuse might modulate cerebral metabolism of cholesterol. This thesis project opens new perspectives on the role of cholesterol cerebral metabolism in addiction which may ultimately result in new therapeutic avenues for the treatment of this costly psychiatric disorder.

Made available in DSpace on 2016-06-02T19:22:03Z (GMT). No. of bitstreams: 1 2282.pdf: 1838286 bytes, checksum: 7d4dd1d44a59556a7f728e6a88087367 (MD5) Previous issue date: 2009-03-05 / Universidade Federal de Minas Gerais / We investigated the interaction between ontogeny, stress and environment where the drug is administered on the behavioral sensitization to cocaine and related neuroadaptations. This study was divided in two parts. In the first one we evaluated the behavioral sensitization to cocaine and alterations of glutamate receptors and tyrosine hydroxylase enzyme following repeated cocaine administrations or stress exposure on adolescent rats. These alterations were evaluated from adolescence to adulthood. The results showed that cocaine administration during adolescence produced long-term behavioral sensitization to cocaine until adulthood and increased of GluR1 glutamate receptor subunit in the medial prefrontal cortex. The stress-induced behavioral sensitization was evident during adolescence but did not reach adulthood. In the second part, we evaluated the environmental modulation of behavioral sensitization to cocaine and alterations of CREB and upstream kinases activation in adult rats. The results showed that the expression of cocaine-induced behavioral sensitization was specific to the environment paired with previous cocaine administration. Moreover, the number of neurons with CREB activation in the nucleus accumbens was increased in sensitized animals and specific to the paired environment. Thus, our results add new findings on addiction related alterations in adolescent animals, its long-term effects and the environmental modulation of cocaine behavioral and neuronal sensitization. / Investigamos a influência da ontogênese, do estresse e do ambiente onde a substância psicoativa é administrada sobre a sensibilização comportamental à cocaína e o desenvolvimento de neuroadaptações. Para tanto, esse trabalho de tese foi dividido em duas partes. Na primeira, avaliamos os efeitos da administração repetida à cocaína ou exposição ao estresse em ratos adolescentes na sensibilização comportamental à cocaína e neuroadaptações dos receptores de glutamato e da enzima tirosina hidroxilase. Essas alterações foram avaliadas durante a adolescência e também acompanhadas até a idade adulta. Demonstramos nesses experimentos que a administração repetida de cocaína durante a adolescência provoca sensibilização comportamental que perdura até a idade adulta e causa aumento da proteína GluR1 dos receptores glutamatérgicos no córtex pré-frontal medial. A exposição ao estresse provoca sensibilização comportamental em adolescentes, mas esse efeito não permanece até a idade adulta. Na segunda parte da tese, avaliamos a influência do pareamento do ambiente onde a cocaína é administrada sobre a expressão da sensibilização comportamental a essa substância e alterações de CREB e enzimas cinases que ativam CREB em ratos adultos. Demonstramos que o pareamento do ambiente com as administrações de cocaína facilita a expressão da sensibilização comportamental. A sensibilização comportamental dependente do ambiente está relacionada ao aumento do número de neurônios com ativação de CREB no núcleo acumbens dos animais. Portanto, nosso estudo pretende contribuir para o entendimento de alterações relacionadas à dependência em animais adolescentes, seus efeitos duradouros e a influência do ambiente onde a substância é administrada.

Made available in DSpace on 2016-06-02T19:23:02Z (GMT). No. of bitstreams: 1 6776.pdf: 1764671 bytes, checksum: 0befe5018516a7acffe79be054e73ae7 (MD5) Previous issue date: 2014-07-07 / Universidade Federal de Minas Gerais / Adolescence marks a period of increased vulnerability to drug abuse. Early initiation of tobacco use is strictly associated with alcohol use and dependence in adolescence and adulthood. The present study aims to investigate: 1) changes in anxiogenic-like effects and on operant ethanol self-administration in adult rats exposed to nicotine during adolescence; 2) changes on pro-dynorphin (PDYN) gene expression in the nucleus accumbens (NAc) on late nicotine withdrawal and after ethanol self-administration; 3) which brain areas are activated on short or long-term nicotine withdrawal during adolescence. Our results showed that pre-exposure to nicotine during ten days (3mg/kg/day; s.c) in adolescent rats, did not change anxiogenic-like effects in the elevated plus maze, 15 days after the treatment cessation [postnatal day (PND) 52], progressive ratio (PND 75-79) and binge (PND 81-84) in the operant ethanol selfadministration protocol. However, animals pre-treated with nicotine displayed increased motivation to saccharin seeking. No changes were observed on gene expression of PDYN 15 days after chronic nicotine treatment cessation or 24 hours after the last binge session of ethanol self-administration. Concerning the areas involved on nicotine withdrawal, we observed that adolescent rats exposed to nicotine through the minipumps during 10 days (PND 28-37), showed enhanced Fos activation in the medial prefrontal cortex (mPFC) 3 days after nicotine treatment cessation (PND 40). The percentage of neuronal activation in this group was 22.03%, of those activated neurons, 28.5% were GABAergic and only 2.5% were glutamatergic neurons. Meanwhile, 15 days after the mini-pumps were removed, no difference was observed on Fos activation in the different brain areas analyzed. We concluded that: a) administration of nicotine during adolescence was not able to modify anxiety-like behaviors and ethanol seeking behavior in adulthood; b) late nicotine withdrawal did not change gene expression of PDYN in NAc, as well as, did not change Fos protein neuronal activation in the regions of mPFC, NAc and habenula; c) short-term nicotine withdrawal involves the activation of neural ensembles in the mPFC. / A adolescência é o período de maior vulnerabilidade ao abuso de drogas. O início precoce do uso de tabaco está significativamente associado ao abuso e dependência de etanol na adolescência e na vida adulta. O presente trabalho teve como objetivo investigar: 1) as alterações nos comportamentos relacionados a ansiedade e na autoadministração operante de etanol em ratos adultos expostos a nicotina durante a adolescência; 2) as alterações na expressão gênica da pró-dinorfina (PDYN) no núcleo acumbens (NAc) na abstinência tardia à nicotina e ao final da autoadministração de etanol; 3) quais as áreas encefálicas ativadas na abstinência, imediata e tardia, à nicotina durante a adolescência. Nossos resultados mostraram que a administração de nicotina durante 10 dias (3mg/kg/dia; s.c), em ratos adolescentes [dia pós-natal (DPN) 28-37], não causou alterações nos comportamentos relacionados a ansiedade no labirinto em cruz elevado 15 dias após a término do tratamento (DPN 52), assim como não alterou a autoadministração operante de etanol na razão progressiva (DPN 75-79) e no binge (DPN 81-84). Contudo, animais pré-tratados com nicotina apresentaram aumento da motivação para a busca de sacarina. Não foram observadas alterações na expressão gênica de PDYN 15 dias após a suspensão do tratamento crônico com nicotina ou 24 horas após a última sessão do binge de etanol. Quanto às áreas envolvidas na abstinência à nicotina, observamos que ratos adolescentes expostos à nicotina, por meio de mini-bombas, durante 10 dias (DPN 28-37), apresentaram maior ativação de Fos no córtex pré-frontal medial (CPFm) 3 dias após o término do tratamento. A porcentagem de ativação neuronal nesse grupo, foi de 22,03%, sendo que 28,5% desses neurônios ativados eram GABAérgicos e apenas 2,5% eram glutamatérgicos. Entretanto, 15 dias após a retirada das mini-bombas não houve diferença na ativação de Fos nas diferentes áreas encefálicas. Concluímos que: a) a administração de nicotina, durante a adolescência, não foi capaz de alterar os comportamentos relacionados a ansiedade e o comportamento de busca pelo etanol na idade adulta; b) a retirada tardia da nicotina não promoveu alterações na expressão gênica de PDYN no NAc, assim como não promoveu alterações na ativação neuronal da proteína Fos nas regiões do CPFm, NAc e habenula; c) a retirada da nicotina a curto prazo envolve a ativação de grupamentos neurais no CPFm.

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