Pharmacological dissociation of trace and long-delay fear conditioning in young rats
Pharmacological dissociation of trace and long-delay fear conditioning in young rats
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DOI：
10.1016/j.nlm.2006.06.003
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发表时间：
2007-01-01
影响因子：
2.7
通讯作者：
Richardson, Rick
中科院分区：
文献类型：
--
作者：
Hunt, Pamela S.;Richardson, Rick
在大多数比较跟踪和延迟条件反射的研究中，CS持续时间在整个训练条件下保持恒定，但刺激间间期（ISI），即从CS发作到US发作的时间，是混淆的。然而，在不经常使用的长延迟条件下，ISI在整个跟踪和延迟条件下保持恒定，但CS持续时间变化。最近的一项研究报告说，跟踪和长延迟恐惧条件反射具有相同的发展轨迹，两者都比标准延迟条件反射在发展后期出现（Barnet & Hunt，2005）。过去的研究表明，跟踪条件反射是由胆碱能系统介导的，鉴于并行发展出现的跟踪和长延迟条件反射，本研究探讨是否胆碱能系统也介导长延迟条件反射。两个实验，都涉及Sprague-Dawley衍生的大鼠和使用冻结作为学习恐惧的措施，表明胆碱能系统是关键参与跟踪条件反射，但不参与长延迟条件反射。具体而言，训练前注射毒蕈碱受体拮抗剂东莨菪碱损害收购的CS-US协会在32天龄的大鼠训练的跟踪程序，但没有影响这个年龄的大鼠训练的长期延迟程序（实验1）。同样，训练前注射毒扁豆碱（一种胆碱酯酶抑制剂）增强了25日龄大鼠的痕量条件反射，但对该年龄大鼠的长延迟条件反射没有影响（实验2）。两者合计，结果表明，尽管痕迹和长延迟条件反射的发育出现和水平的条件反应方面的相似之处，它们是由不同的生理系统介导的。(c)2006年爱思唯尔公司All rights reserved.
In most studies comparing trace and delay conditioning, CS duration is kept constant across training conditions but the interstimulus interval (ISI), the time from CS onset to US onset, is confounded. In the infrequently used long-delay condition, however, ISI is kept constant across the trace and delay conditions but CS duration varies. A recent study reported that trace and long-delay fear conditioning have the same developmental trajectory, with both emerging later in development than standard-delay conditioning (Barnet & Hunt, 2005). Past studies have shown that trace conditioning is mediated by the cholinergic system; given the parallel developmental emergence of trace and long-delay conditioning, the present study examined whether the cholinergic system also mediates long-delay conditioning. Two experiments, both involving Sprague-Dawley-derived rats and using freezing as a measure of learned fear, showed that the cholinergic system is critically involved in trace conditioning but is not involved in long-delay conditioning. Specifically, pre-training injections of the muscarinic receptor antagonist scopolamine impaired acquisition of a CS-US association in 32-day-old rats trained with a trace procedure but had no effect on rats this age trained with a long-delay procedure (Experiment 1). Similarly, pre-training injections of physostigmine, a cholinesterase inhibitor, enhanced acquisition of trace conditioning in 25-day-old rats but had no effect on long-delay conditioning in rats this age (Experiment 2). Taken together, the results indicate that despite the similarities between trace and long-delay conditioning in terms of developmental emergence and level of conditioned responding, they are mediated by different physiological systems. (c) 2006 Elsevier Inc. All rights reserved.