The present study examined the effects of the muscarinic acetylcholine receptor (mAChR) antagonist, scopolamine, on standard contextual fear conditioning (sCFC). It compared effects of the drug on acquisition (post-shock freezing) versus 24-hr retention of a context-shock association acquired after one or three pairings of a context with unsignaled shock. During single-trial sCFC, systemic scopolamine (0.5 mg/kg, i.p.) prior to training abolished both post-shock and retention freezing (Experiment 1). This same injection during multiple-trial sCFC also abolished post-shock freezing and impaired 24-hr retention freezing (Experiment 2). These results indicate that cholinergic signaling mediates both acquisition and 24-hr retention of a context-shock association across different trial parameters. Experiment 3 further explored these effects by infusing scopolamine (35 μg per side) into the dorsal hippocampus (dHPC) prior to training in single versus multiple-trial sCFC. This infusion spared post-shock but abolished retention test freezing in single-trial sCFC (Experiment 3A), and had no effect on multiple-trial sCFC (Experiment 3B). The current findings suggest that brain-wide cholinergic signaling mediates acquisition and retention of single-trial sCFC. Despite this, while muscarinic cholinergic signaling in the dHPC does mediate retention of single-trial sCFC, it is not required for acquisition of either variant, or retention of multiple-trial sCFC. These findings also rule out impaired sensory processing of contextual cues as a mechanism of impaired context learning by dHPC scopolamine. The results are discussed in relation to the role of cholinergic function across multiple brain memory systems in elemental versus configural forms of contextual fear conditioning (Fanselow, 2010; Rudy, 2009). (PsycInfo Database Record (c) 2021 APA, all rights reserved).

中文翻译：

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背侧海马毒蕈碱受体活性在青少年大鼠单次与多次试验情境恐惧条件反射的获得和保留中的作用。

本研究检查毒蕈碱乙酰胆碱受体 (mAChR) 拮抗剂东莨菪碱对标准情境恐惧条件反射 (sCFC) 的影响。它比较了药物对获取（电击后冻结）的影响与在无信号电击的一或三个配对后获得的上下文电击关联的 24 小时保留。在单次试验 sCFC 期间，训练前全身性东莨菪碱（0.5 毫克/千克，腹腔注射）消除了休克后和滞留冻结（实验 1）。在多次试验 sCFC 期间进行的相同注射也消除了电击后冷冻和 24 小时保留冷冻受损（实验 2）。这些结果表明胆碱能信号介导了不同试验参数的上下文休克关联的获取和 24 小时保留。实验 3 通过在单次试验与多次试验 sCFC 训练之前将东莨菪碱（每侧 35 μg）注入背海马体 (dHPC) 来进一步探索这些影响。这种输液在单次试验 sCFC（实验 3A）中避免了电击后的保留试验冻结（实验 3A），并且对多次试验 sCFC（实验 3B）没有影响。目前的研究结果表明，全脑胆碱能信号介导单次试验 sCFC 的获取和保留。尽管如此，虽然 dHPC 中的毒蕈碱胆碱能信号确实介导了单次试验 sCFC 的保留，但它不是获取任何变体或保留多次试验 sCFC 所必需的。这些发现还排除了上下文线索的感觉处理受损作为 dHPC 东莨菪碱受损上下文学习的机制。结果讨论了胆碱能功能在多个大脑记忆系统中的作用，在基本形式与结构形式的情境恐惧条件反射中的作用（Fanselow，2010；Rudy，2009）。（PsycInfo 数据库记录 (c) 2021 APA，保留所有权利）。