Navegando por Palavras-chave "AP5"

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    Effects of Pre or Posttraining Dorsal Hippocampus D-AP5 Injection on Fear Conditioning to Tone, Background, and Foreground Context
    (Wiley-Blackwell, 2008-01-01) Schenberg, Eduardo Ekman [UNIFESP]; Menezes Oliveira, Maria Gabriela [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    NMDA receptor antagonist D-AP5 was injected into the dorsal hippocampus of Wistar rats before or immediately after the training session in fear conditioning. Training was conducted both with signaled (background context) or unsignaled (foreground context) footshocks. Contextual fear conditioning was assessed 24 h later and tone fear conditioning 48 h after training (only in the signaled footshock condition). Pretraining injections impaired conditioned fear to contextual features, both in background and foreground configurations, whereas tone fear conditioning was left intact. Posttraining injections were ineffective in all cases. We conclude that dorsal hippocampal NMDA receptors are required for contextual fear acquisition independently of context saliency and that they are not required to early consolidation processes. (C) 2008 Wiley-Liss, Inc.
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    Effects of pre- or post-training entorhinal cortex AP5 injection on fear conditioning
    (Elsevier B.V., 2005-11-15) Schenberg, E. E.; Soares, JCK; Oliveira, MGM; Universidade Federal de São Paulo (UNIFESP)
    Fear conditioning is one of the most studied paradigms to assess the neural basis of emotional memory. the circuitry involves NNMA receptor activation in the amygdala and, in the case of contextual conditioning, in the hippocampus. Entorhinal cortex is one of the major input/output structures to the hippocampus and also projects to the amygdala, both through glutamatergic transmission. Other learning tasks involving hippocampus and amygdala, such as inhibitory avoidance, require entorhinal cortex during acquisition and consolidation. However, the involvement of NMDA receptors mediated transmission in entorhinal cortex in fear conditioning acquisition and consolidation is not clear. To investigate that issue, rats were trained in fear conditioning to both contextual and tone conditioned stimulus. Immediately before, immediately, 30 or 90 min after training they received NMDA antagonist AP5 or saline injections bilaterally in the entorhinal cortex (AP-6.8 mm, L +/- 5.0 mm DV-6.8 mm). Contextual fear conditioning was measured 24 h after training, and tone fear conditioning 48 h after training. AP5 injections selectively impaired contextual fear conditioning only when injected pre-training. Post-training injections had no effect. These findings suggest that entorhinal cortex NMDA receptors are necessary for acquisition, but not for consolidation, of contextual fear conditioning. On the other hand, both acquisition and consolidation of tone fear conditioning seem to be independent of NMDA receptors in the entorhinal cortex. (c) 2005 Elsevier Inc. All fights reserved.
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    Hippocampal NMDA receptor blockade impairs CREB phosphorylation in amygdala after contextual fear conditioning
    (Wiley-Blackwell, 2013-07-01) Oliveira Coelho, Cesar Augusto de [UNIFESP]; Ferreira, Tatiana Lima; Kramer Soares, Juliana Carlota [UNIFESP]; Menezes Oliveira, Maria Gabriela [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    In contextual fear conditioning (CFC), hippocampus is thought to process environmental stimuli into a configural representation of the context and send it to amygdala nuclei, which current evidences point to be the site of CS-US association and fear memory storage. If it is true, hippocampus should influence learning-induced plasticity in the amygdala nuclei after CFC acquisition. To test this, we infused wistar rats with saline or AP5, a NMDA receptor antagonist, in the dorsal hippocampus just before a CFC session, in which they were conditioned to a single shock, exposed to the context with no shocks or received an immediate shock. the rats were perfused, their brains harvested and immunohistochemically stained for cAMP element binding protein (CREB) phosphorylation ratio (pCREB/CREB) in lateral (LA), basal (B) and central (CeA) amygdala nuclei. CFC showed a learning-specific increase in pCREB ratio in B and CeA, in conditioned-saline rats compared to context and immediate shocked ones. Further, conditioned rats that received AP5 showed a decrease in pCREB ratio in LA, B and CeA. Our results support the current ideas that the role of hippocampus in contextual fear conditioning occurs by sending contextual information to amygdala to serve as conditioned stimulus. (c) 2013 Wiley Periodicals, Inc.