Department of Psychology, University of Wisconsin-Eau Claire, Eau Claire, WI 54701, USA.
Faculty of Science and Engineering, University of Waikato, Hamilton 3240, New Zealand.
Nutrients. 2022 Feb 22;14(5):926. doi: 10.3390/nu14050926.
The opioid antagonist naltrexone (NTX) decreases intake of preferred diets in rats at very low doses relative to doses needed to decrease intake of "bland" laboratory chow. In the absence of an opioid agonist, NTX is not discriminable using operant techniques. In the current study, we found that rats given intermittent access to a 25% sucrose solution learned to discriminate between various naltrexone doses and saline. None of the rats given only water learned to discriminate between naltrexone and saline. When access to the sucrose solution was discontinued for 14 days, the rats lost the ability to discriminate between NTX and saline. We also studied the changes of c-Fos IR in selected brain regions in rats treated with saline versus NTX that were drinking water or 25% sucrose. An injection of NTX or saline resulted in a significant drug, diet, and interaction effect in various brain regions associated with feeding behavior, particularly the amygdala, accumbens, and hypothalamic sites. Thus, we found that ingestion of a sucrose solution results in the ability of rats to reliably discriminate naltrexone administration. In addition, sucrose and naltrexone altered c-Fos IR in an interactive fashion in brain regions known to be involved in ingestion behavior.
阿片受体拮抗剂纳曲酮（NTX）在非常低的剂量下就能减少大鼠对“无味”实验室饲料的摄入量，而所需的剂量低于减少对“无味”实验室饲料的摄入量。在没有阿片类激动剂的情况下，纳曲酮不能通过操作性技术来区分。在目前的研究中，我们发现，给予间歇性接触 25%蔗糖溶液的大鼠学会了区分不同的纳曲酮剂量和生理盐水。没有一只只给水的大鼠学会区分纳曲酮和生理盐水。当蔗糖溶液的摄入停止 14 天后，大鼠失去了区分纳曲酮和生理盐水的能力。我们还研究了接受生理盐水或纳曲酮治疗的大鼠在饮用水或 25%蔗糖时，选择的大脑区域中 c-Fos IR 的变化。纳曲酮或生理盐水的注射在与摄食行为相关的各种大脑区域中产生了显著的药物、饮食和相互作用效应，特别是杏仁核、伏隔核和下丘脑部位。因此，我们发现，摄入蔗糖溶液可使大鼠能够可靠地区分纳曲酮的给药。此外，蔗糖和纳曲酮以交互的方式改变了已知参与摄食行为的大脑区域中的 c-Fos IR。
