Baldi Elisabetta, Bucherelli Corrado
Dipartimento di Medicina, Sperimentale e Clinica, Sezione di Fisiologia, Università degli Studi di Firenze, Viale G.B. Morgagni 63, I-50134 Firenze, Italy.
Dipartimento di Medicina, Sperimentale e Clinica, Sezione di Fisiologia, Università degli Studi di Firenze, Viale G.B. Morgagni 63, I-50134 Firenze, Italy.
Neurobiol Learn Mem. 2014 Apr;110:64-71. doi: 10.1016/j.nlm.2014.02.004. Epub 2014 Feb 22.
During contextual fear conditioning a rat learns a temporal contiguity association between the exposition to a previously neutral context (CS) and an aversive unconditioned stimulus (US) as a footshock. This condition determines in the rat the freezing reaction during the subsequent re-exposition to the context. Potentially the re-exposition without US presentation initiates two opposing and competing processes: reconsolidation and extinction. Reconsolidation process re-stabilizes and strengthens the original memory and it is initiated by a brief re-exposure to context. Instead the extinction process leads to the decrease of the expression of the original memory and it is triggered by prolonged re-exposure to the context. Here we analyzed the entorhinal cortex (ENT) participation in contextual fear conditioning reconsolidation and extinction. The rats were trained in contextual fear conditioning and 24h later they were subjected either to a brief (2 min) reactivation session or to a prolonged (120 min) re-exposition to context to induce extinction of the contextual fear memory. Immediately after the reactivation or the extinction session, the animals were submitted to bilateral ENT TTX inactivation. Memory retention was assessed as conditioned freezing duration measured 72 h after TTX administration. The results showed that ENT inactivation both after reactivation and extinction session was followed by contextual freezing retention impairment. Thus, the present findings point out that ENT is involved in contextual fear memory reconsolidation and extinction. This neural structure might be part of parallel circuits underlying two phases of contextual fear memory processing.
在情境恐惧条件反射过程中，大鼠学习到先前中性情境（条件刺激，CS）与厌恶非条件刺激（非条件刺激，US，如足部电击）之间的时间连续性关联。这种条件在大鼠随后再次暴露于该情境时决定了其冻结反应。在没有呈现非条件刺激的情况下再次暴露可能引发两个相反且相互竞争的过程：重新巩固和消退。重新巩固过程会重新稳定并强化原始记忆，它由短暂再次暴露于情境引发。相反，消退过程会导致原始记忆表达的减少，它由长时间再次暴露于情境触发。在这里，我们分析了内嗅皮质（ENT）在情境恐惧条件反射的重新巩固和消退中的参与情况。大鼠接受情境恐惧条件反射训练，24小时后，它们要么接受短暂（2分钟）的重新激活训练，要么长时间（120分钟）再次暴露于情境以诱导情境恐惧记忆的消退。在重新激活或消退训练后立即对动物进行双侧ENT的TTX失活处理。记忆保持通过在给予TTX后72小时测量的条件性冻结持续时间来评估。结果表明，在重新激活和消退训练后进行ENT失活均会导致情境冻结保持受损。因此，本研究结果指出ENT参与了情境恐惧记忆的重新巩固和消退。这种神经结构可能是情境恐惧记忆处理两个阶段基础的并行回路的一部分。
