Efeitos comportamentais da administração de nicotina em duas variantes do condicionamento de medo ao contexto em ratos.

• Autor(a) principal: Leonessa Alves, Fabio Augusto [UNIFESP]
• Data de Publicação: 2019
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Repositório Institucional da UNIFESP
• Texto Completo: https://sucupira.capes.gov.br/sucupira/public/consultas/coleta/trabalhoConclusao/viewTrabalhoConclusao.jsf?popup=true&id_trabalho=7655269; https://repositorio.unifesp.br/handle/11600/58741
• topic: Memory; Contextual fear conditioning; Nicotine; Hippocampus; Memória; Condicionamento de medo ao contexto; Condicionamento de traço; Nicotina; Hipocampo

A task called contextual fear conditioning with temporal discontinuity (CFC-5s) was developed in our lab. In this task, the association between the context and the aversive stimulus is done discontinuously in time, with a 5s interval between the stimuli. This task differs from contextual fear conditioning (CFC), in which stimuli to be associated overlap. It also differs from CFC because it requires the integrity of the pre-limbic cortex (PL) to occur. Because nicotine (NIC) has been shown to facilitate the learning of hippocampal dependent tasks and other associations done discontinuously in time, such as trace fear conditioning, as well as CFC itself, it could also facilitate the learning of CFC-5s, and so in a different manner, as a dosedependent manner, from CFC. The aim of the present study was to analyze whether acute NIC administration affects the acquisition or retrieval of CFC-5s at the same doses that affects CFC. For this, male Wistar rats at 3 months-old received saline (SAL group) or NIC at doses of 0.1, 0.4 and 1 mg / kg 15 min before training session in Experiment 1; 15 min before training and test sessions in Experiment 2 or 15 min before test session in Experiment 3. The latter only used the intermediate dose of NIC (0.4 mg / kg). Independent groups of animals were trained in CFC or CFC-5s tasks. The CFC training consisted of placing the animal in the context for 5 min deliverying a footshock at the end. The CFC-5s training consisted of placing the animal in the context for 5 min, to remove it from the context for 5 seconds, and then replace it in the context delivering an immediate footshock. In test sessions, animals were allowed to stay in the context for 5 minutes in Experiment 1 and 15 minutes in Experiments 2 and 3 and freezing responses were used as the conditioned response. Data were analyzed by Generalized Estimating Equations (GEE) followed by LSD post hoc test when necessary. Pre-training NIC administration impaired CFC, but not CFC-5s. Pre-training and pre-testing NIC administration improved both CFC and CFC-5s in the first minutes, but impaired in the last one. However, each task was impaired by different NIC doses. Pre-training and pre-testing NIC administration also delayed the extinction of CFC, but not CFC-5s. Pre-testing NIC administration facilitated both tasks. These results suggest that acute administration of NIC affects the tasks differentially and then that the insertion of a time interval modifies the neurobiology of CFC.