Swank M W, Schafe G E, Bernstein I L
Department of Psychology, University of Washington, Seattle 98195, USA.
Brain Res. 1995 Mar 6;673(2):251-61. doi: 10.1016/0006-8993(94)01421-d.
Amphetamine and lithium chloride (LiCl) are both effective unconditioned stimuli (USs) in the establishment of conditioned taste aversions (CTA) in the rat. However, the mechanism of action of these drugs is quite different with the area postrema and related emetic circuitry critical to the response to LiCl but not amphetamine. c-Fos immunohistochemistry was used to define brain regions activated during drug administration and during expression of a CTA using either amphetamine or LiCl as the US drug. Administration of LiCl induced dense c-Fos-like immunoreactivity (c-FLI) in the nucleus of the solitary tract (NTS) while amphetamine induced only light staining in this area. A conditioned stimulus (CS) saccharin solution paired with amphetamine, however, was associated with c-FLI in NTS in a pattern quite similar to that seen to a LiCl-paired CS. This suggests that the pattern of c-Fos expression to a taste CS after conditioning is characteristic of aversion conditioning, in general, and appears not to represent a matching of the conditioned response to specific unconditioned effects of the drug. To examine this conditioned response further, c-FLI to the aversive saccharin CS was compared to the response to quinine hydrochloride, which is innately aversive. Although behaviorally the animals' ingestive responses were quite similar, the saccharin CS induced significant elevations of c-FLI in NTS whereas the quinine did not. Thus, a taste which had become aversive by virtue of conditioning induced c-FLI expression in NTS while a taste which was inherently aversive did not.
苯丙胺和氯化锂（LiCl）在大鼠条件性味觉厌恶（CTA）的建立中都是有效的非条件刺激（USs）。然而，这些药物的作用机制有很大不同，最后区及相关催吐神经回路对LiCl的反应至关重要，但对苯丙胺则不然。采用c-Fos免疫组织化学法来确定在给药期间以及使用苯丙胺或LiCl作为US药物时CTA表达期间被激活的脑区。给予LiCl可在孤束核（NTS）诱导密集的c-Fos样免疫反应性（c-FLI），而苯丙胺在此区域仅诱导轻度染色。然而，与苯丙胺配对的条件刺激（CS）糖精溶液与NTS中的c-FLI相关，其模式与与LiCl配对的CS所见模式非常相似。这表明，一般来说，条件化后对味觉CS的c-Fos表达模式是厌恶条件化的特征，似乎并不代表条件反应与药物特定非条件效应的匹配。为了进一步研究这种条件反应，将对厌恶糖精CS的c-FLI与对天生具有厌恶感的盐酸奎宁的反应进行了比较。尽管在行为上动物的摄食反应非常相似，但糖精CS在NTS中诱导c-FLI显著升高，而奎宁则没有。因此，通过条件化变得厌恶的味觉在NTS中诱导c-FLI表达，而天生厌恶的味觉则不会。
