Bilgi Toplumu Çağın Üçüncü Kuşak ve Girişimci Üniversiteleri

50 LEMOS, N. A. M. ; GALLI, M. ; SILVA, R. H. ; RIBEIRO, S. Aversive extinction differences after training and retraining sessions on the discrimintative avoidance task.

In: 2nd Neuroscience Symposium of the International Institute for Neuroscience of Natal, 2007, Natal. Annals of 2nd Neuroscience Symposium of the International Institute

for Neuroscience of Natal, 2007. v. 2. p. 301.

Resumo: The plus-maze discriminative avoidance task has been validated as a new

model to study memory and anxiety. In this paradigm, learning and long-term retention have been extensively studied. Here we focused on adapting this model for short intervals between sessions (1 hour), introducing re-training and re-testing sessions to study memory extinction and re-acquisition. Our aim was to enable further experimentation in animals chronically implanted with intracranial electrode arrays. Our modified plus-maze has its enclosed arms disposed in “L”. At the beginning of each session, animals (n=9) were placed in a box for 1 hour. Pre-exposure to the apparatus was performed with all arms closed. Training, test1, test2, re-training, re-test1 and re- test2 sessions followed. All sessions lasted 10 minutes. During training and re-training sessions, aversive stimuli (bright light and loud noise) were delivered whenever an animal entered one of the enclosed arms (aversive arm). The experiment was performed during the dark phase of the light/dark cycle. Acquisition, retention and extinction were evaluated by the percent of the total time spent in the aversive arm. Number of entries and time spent in each arm were registered by an animal tracking software (Anymaze, Stoelting, USA). Learning in the training session was estimated as the decrease in time spent in the aversive arm. In summary, the modified model with 1 hour interval between sessions seems adequate to study memory processes in animals chronically implanted with multielectrode arrays.

LEMOS, N. A. M. ; GALLI, M. ; SILVA, R. H. ; RIBEIRO, S. . Extinção da tarefa após o treino e o retreino da tarefa de esquiva discriminativa. In: II Reunião Regional da

Fesbe, 2007, Recife. Anais da II Reunião Regional da Fesbe, 2007. p. 10.034.

Objetivo: The plus-maze discriminative avoidance task has been validated as a new

model to study memory and anxiety. In this paradigm, learning and long-term retention have been extensively studied. Here we focused on adapting this model for short intervals between sessions (1 hour), introducing re-training and re-testing sessions to study memory extinction and re-acquisition. Another aim was to enable further experimentation in animals chronically implanted with intracranial electrode arrays.

Métodos e Resultados: Our modified plus-maze has its enclosed arms disposed in “L”.

At the beginning of each session, animals (n=9) were placed in a box for 1 hour. Pre- exposure to the apparatus was performed with all arms closed. Training, test1, test2, re- training, re-test1 and re-test2 sessions followed. All sessions lasted 10 minutes. During training and re-training sessions, aversive stimuli (bright light and loud noise) were delivered whenever an animal entered one of the enclosed arms (aversive arm). The experiment was performed during the dark phase of the light/dark cycle. Acquisition, retention and extinction were evaluated by the percent of the total time spent in the aversive arm. Number of entries and time spent in each arm were registered by an animal tracking software (Anymaze, Stoelting, USA). Learning in the training session was estimated as the decrease in time spent in the aversive arm. Our results show that memory extinction occurred at test and re-test phases, being less robust after re- training. Total entries decreased along the sessions, indicating habituation.

Conclusões: The modified model with 1 hour intervals between sessions seems

adequate to study memory processes at shorter intervals, enabling studies in animals chronically implanted with multielectrode arrays.

52 LEMOS, N. A. M. ; FREIRE, M. ; NICOLESIS, M. A. L. ; SILVA, R. H. ; RIBEIRO, S. . Immediate Early Gene Expression During the Acquisition, Extinction and Re-Acquisition of an Aversive Memory. In: XXII Reunião Anual da Fesbe, 2007, Águas de Lindóia. Anais da XXII Reunião Anual da Fesbe,

2007. p. 05.152.

Objetivo: The plus-maze discriminative avoidance task with re-training and re-test

sessions is a good model to investigate memory acquisition, extinction and re- acquisition. Calcium-dependent immediate early genes (IEGs) involved in synaptic plasticity, such as zif-268 and c-fos, can be used to assess brain sites where learning occurs. Here we set out to investigate the dynamics of calcium-dependent IEG expression during different learning/unlearning phases of the plus-maze discriminative avoidance task.

Métodos e Resultados: Animals were pre-exposed to the maze with all four arms

closed to habituate responses to novelty and thus decrease basal levels of IEG expression. Training, test1, test2, re-training, re-test1 and re-test2 sessions were investigated (session duration = 10 min). Experiments were performed during the dark phase of the light/dark cycle, with a 24 hours interval between sessions. During training and re-training sessions, aversive stimuli (bright light and loud noise) were presented whenever an animal entered one of the enclosed arms (aversive arm). At the end of target sessions, animals were placed back in their home cages and perfused after additional 50 minutes with phosphate-saline buffer and 4% paraformaldehyde. The tissue was then frontally sectioned at 20 µm in a cryostat and submitted to immunohistochemistry for zif-268 and c-fos. Our preliminary results show that cells in the CA1 field of the hippocampus – but not in other hippocampal regions - were strongly labeled for zif-268 and c-fos during the training. Such labeling decreased across the subsequent sessions.

Conclusões: The data suggest that the CA1 field of the hippocampus encodes aversive

memories created during the plus-maze discriminative avoidance task.

LEMOS, N. A. M. ; FREIRE, M. ; NICOLESIS, M. A. L. ; SILVA, R. H. ; RIBEIRO, S. . Immediate Early Gene Expression During the Acquisition, Extinction and Re-Acquisition of an Aversive Memory. In: XXII Reunião Anual da Fesbe, 2007, Águas de Lindóia. Anais da XXII Reunião Anual da Fesbe,

2007. p. 05.152. Apresentado sob forma de comunicação oral no módulo temático "Contexto emocional na formação de memórias".

LEMOS, N.A.M., FREIRE, M.A.M., FERREIRA, L.F., NICOLELIS, M.A.L., SILVA, R.H.,

RIBEIRO, S. Expressao do gene imediato Zif-268 durante a aquisicao, evocacao e

extincao de uma memoria aversiva. In: III Reunião Regional da Fesbe, 2007, Recife.

Objetivos: No paradigma comportamental da esquiva discriminativa, as memórias de

curto e de longo prazo têm sido extensivamente estudadas tanto comportamental quanto farmacologicamente (J. Neurosci. Meth. 102: 117, 2000). O objetivo do presente estudo é avaliar, usando o modelo supracitado, a expressão hipocampal de Zif-268 – gene imediato dependente de cálcio implicado em processos de plasticidade sináptica – ao longo das diversas etapas da formação da memória, como aquisição, evocação e extinção.

Métodos e resultados: O aparato comportamental consiste de um labirinto em cruz

elevado modificado, com seus braços fechados dispostos em “L”. Uma pré-exposição ao labirinto foi feita com os animais (n=3/grupo) usando os quatro braços fechados, com duração de 30 minutos, seguida de um treino e de um teste, cada qual com duração de 10 minutos. O intervalo entre as sessões foi de 24 horas. Durante o treino, um estímulo aversivo (luz e ruído intensos) era acionado sempre que os animais entravam em um dos braços fechados (braço aversivo). A aquisição, retenção e extinção da memória foram avaliados pelo percentual de tempo total gasto na exploração do braço aversivo. Os parâmetros avaliados (tempo nos braços e distância percorrida) foram registrados por um software de rastreamento de animais (Anymaze, Stoelting, USA). O aprendizado durante o treino foi estimado pelo decréscimo do tempo gasto na exploração o braço aversivo. Uma hora após o início de cada sessão, os animais foram anestesiados com uma overdose de tiopental (i.p.) e perfundidos com solução salina heparinizada 0.9% e paraformaldeído a 4%. Os encéfalos foram crioprotegidos com solução de sacarose a 20%, separados em três blocos e congelados. O bloco do meio, contendo o hipocampo, foi seccionado a 20 µm no plano coronal e as secções resultantes foram então submetidas à imunohistoquímica para Zif-268. Nossos resultados mostram um aumento da expressão de Zif-268 no giro denteado (GD) durante as etapas de evocação e extinção.

Conclusões: Há uma participação distinta do giro denteado durante a evocação e

extinção da memória, mas não durante a aquisição. Além disso, todas as áreas hipocampais (CA1, CA3 e GD) apresentam uma elevação da expressão de Zif-268 durante o processo de extinção.

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