Efeitos do ambiente enriquecido sobre a memória aversiva e a imunorreatividade para ZIF-268 e tirosina hidroxilase no sistema mesocorticolímbico de ratos

• Ano de defesa: 2017
• Autor(a) principal: Cavalcante, Karenine Maria Holanda
• Orientador(a): Marchioro, Murilo
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Programa de Pós-Graduação: Pós-Graduação em Ciências Fisiológicas
• Palavras-chave em Português: Memória; Medo; Cortex cerebral; Neuroplasticidade; Sistema dopaminérgico; Ambiente; Córtex pré-frontal; Plasticidade neuronal; Agentes dopaminérgicos
• Palavras-chave em Inglês: Environment; Memory; Fear; Prefrontal cortex; Neural plasticity; Dopamine agents
• Área do conhecimento CNPq: CIENCIAS BIOLOGICAS::FISIOLOGIA
• Link de acesso: http://ri.ufs.br/jspui/handle/riufs/12588

Environmental enrichment (EE) provides visual, motor, somatosensory, cognitive stimuli, besides favoring social relationships. It is an interesting model to understand mechanisms underlying the plasticity of the brain in laboratory animals. EE reduces sensitivity to loss of reward by reducing frustration-like emotional states in rats, and also favors coping strategies, facilitating the extinction of context conditioned fear memory. The present study aimed to analyze the effects of EE on the emotional memory in situation of context conditioned fear and on the neurons of the mesocorticolimbic system in young adult Wistar rats. The research was organized in two experiments: the Experiment I, aimed to identify the effects of short and medium-term EE on the expression of fear and on the neurons of the mesocorticolimbic system; while the Experiment II, aimed to evaluat the effects of dopaminergic modulation in the infralimbic cortex (IL) on the extinction of fear in rats submitted to short-term EE. In the first experiment, 36 male rats were divided into three groups (n = 12): control (Ctr), short-term EE (EE2), two weeks duration, and medium-term EE (EE4), four weeks duration. The groups were submitted to the contextual fear conditioning test (CFC), divided into three phases: Conditioning, Evocation (Session 1) and Extinction (Session 2). Immunohistochemical studies were performed for ZIF 268 and TH in areas of mesocorticolimbic system. In the second experiment, 72 male rats were distributed in six groups (n = 12): saline control, haloperidol control, apomorphine control, saline EE, haloperidol EE, apomorphine EE, and they were submitted to the same CFC protocol. In this experiment, EE lasted 2 weeks. We showed that the EE changed the defensive behavior of the animals in the coping of unconditioned aversive situations, such as a new environment and the presence of electric shock stimuli. Animals previously maintained for two or four weeks in EE had changes in the behavior in situation of contextual fear conditioning. When previously held for two weeks in EE, the animals exhibited a favoring of extinction of context-dependent fear, reducing freezing time on the extinction test session. We observed alterations regarding neuroplastic aspects in the mesocorticolimbic areas, such as hippocampus and amygdala, after submitting the animals to EE. However, only EE2 reduced the Ziif-268 expression in VTA. We identified that EE provided an increase in the pattern of TH expression in VTA and NAcc and that only EE2 changed its expression in areas such as hippocampus and IL. Finally, the injection of apomorphine, dopamine agonist, and haloperidol, a dopamine D2 receptor antagonist, in the IL cortex of animals submitted to EE for two weeks, made it difficult to extinguish contextual fear conditioned. Thus, EE changes the defensive behavior and emotional memory of rats, and the duration of EE interferes differently. The lack of benefit on the coping of the animals submitted to medium-term EE suggests a tolerance to the emotionally positive effects of EE. Dopaminergic modulation in IL cortex is involved in the coping improvement resulting from short-term EE