An unexpected reduction in sucrose concentration activates the HPA axis on successive post shift days without attenuation by discriminative contextual stimuli
An unexpected reduction in sucrose concentration activates the HPA axis on successive post shift days without attenuation by discriminative contextual stimuli
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DOI：
10.1016/j.physbeh.2008.12.018
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发表时间：
2009-03-23
影响因子：
2.9
通讯作者：
Dallman, Mary F.
中科院分区：
文献类型：
--
作者：
Pecoraro, Norman;de Jong, Hanna;Dallman, Mary F.
先前的研究表明，在连续的阴性对照过程中，限制食物的大鼠每天被短暂地喂食一次32%的蔗糖，意外地转移到4%的溶液中。结果肾上腺皮质反应发生在第二天，而不是第一天。我们试图在自己的程序中推广这一发现。在实验1中，两组大鼠在其家庭笼子中每天给予一次32%的蔗糖溶液，持续14天，然后转移到4%的溶液。一组在第一次4%溶液后10 min死亡，另一组在第二次4%溶液后死亡。此外，在整个实验过程中，两组接受32%或4%蔗糖的小鼠作为未转移的对照组。与之前的研究结果相反，与未移位的对照组相比，两个移位组在轮班后两天都表现出显著的促肾上腺皮质激素（ACTH）和肾上腺皮质(B)反应，两者之间没有差异。实验2a采用不同的情境来测试延迟HPA轴反应缺乏普遍性是否由于S（+）在轮班后第一天的抑制作用。S（+）中给予32%蔗糖，S（-）中给予等量暴露时间，每天1次。这些大鼠中的一半被转移到S（+）中4%的蔗糖，一半被转移到S（-）中。这两组与家庭笼对照进行比较。每组中有一半在第一次摄入4%蔗糖后死亡，一半在第二次摄入4%蔗糖后死亡。实验1中所有大鼠的ACTH和B反应与移位大鼠相当。S（+）不能抑制HPA轴，第一天的应激反应高于第二天。实验2b证实，预测蔗糖含量为S（+）或不预测蔗糖含量为5（-）的不同情境控制了行为选择和情境歧视。因此，没有证据表明刺激控制的问题可以解释先前发现的缺乏普遍性。数据表明，抑制对蔗糖的预期是有压力的，这种压力反应会持续数天。(c) 2008爱思唯尔公司版权所有。
Previous studies have shown that the successive negative contrast procedure, in which food-restricted rats entrained to once daily, brief presentations of 32% sucrose are unexpectedly shifted to a 4% solution. results in an adrenocortical response on the second, but not the first postshift day. We attempted to generalize that finding in our own procedure. In Experiment 1, two groups of rats were given a 32% sucrose solution once daily in their home cages for 14 days before being shifted to a 4% solution. One group was killed 10 min after the first 4% solution and one was killed after the second 4% solution. In addition, two groups receiving either 32% or 4% sucrose throughout the experiment served as unshifted controls. In contrast to previous findings, both shifted groups exhibited prominent adrenocorticotropin hormone (ACTH) and adrenocortical (B) responses on both postshift days compared to unshifted controls, which did not differ from one another. Experiment 2a employed distinctive contexts to test if the lack of generality of the delayed HPA axis response was due to suppressive effects of S(+) on the first postshift day. Rats were given once daily 32% sucrose in S(+) and equal exposure time in S(-). Half of these rats were shifted to 4% sucrose in S(+) and half were shifted in S(-). These two groups were compared to home cage controls. Half of each group was killed after their first 4% sucrose, and half after the second 4% sucrose. All rats showed ACTH and B responses comparable to shifted rats in Experiment 1. S(+) failed to suppress the HPA axis, and the stress response was higher on the first compared to the second day of the shift. Experiment 2b established that distinctive contexts predicting sucrose, S(+), or not predicting sucrose, 5(-), controlled behavioral choice and contextual discrimination. Thus, there was no evidence that issues of stimulus control could explain the lack of generality of previous findings. The data indicate that thwarting sucrose expectancies is stressful, and that this stress response habituates across days. (c) 2008 Elsevier Inc. All rights reserved.