Department of Neurobiology and Behavior, University of California Irvine, Irvine, California, USA.
Addict Biol. 2021 Nov;26(6):e13024. doi: 10.1111/adb.13024. Epub 2021 Feb 23.
E-cigarettes, which deliver vaporized nicotine, have dramatically risen in popularity in recent years, despite many unanswered questions about safety, efficacy in reducing dependence, and overall impact on public health. Other factors, such as sex, also play an important role in determining behavioral and neurochemical responses to drugs of abuse. In these studies, we sought to develop a protocol for vaporized e-cigarette nicotine self-administration in rats, as a foundation to better understand the differing effects of nicotine exposure routes on behavior and physiological function. We report a novel method that elicits robust nicotine vapor self-administration in male and female rats. Our findings indicate that 5-mg/ml nicotine vape solution provides a high level of consistency in lever-pressing behavior for both males and females. Moreover, in male rats, we find that such e-cigarette nicotine vapor induces similar blood levels of nicotine's main metabolite, cotinine, as that found with intravenous nicotine self-administration. Therefore, the breathing pattern during vapor exposure in males leads to similar levels of titrated nicotine intake as with intravenous nicotine self-administration. Interestingly, a differential effect was found in the females, in which the same conditions of vapor exposure led to decreased cotinine levels with vapor compared to intravenous self-administration. Finally, differences in nicotine-mediated locomotion provide further support of the physiological effects of e-cigarette vapor inhalation. Taken together, our findings reveal important sex differences in nicotine intake based on the route of exposure, and we further establish a protocol for nicotine vapor self-administration in rats.
电子烟通过蒸发尼古丁来提供尼古丁,近年来其受欢迎程度急剧上升,尽管对于安全性、减少依赖的功效以及对公共健康的整体影响等方面仍有许多尚未解答的问题。其他因素,如性别,在确定对滥用药物的行为和神经化学反应方面也起着重要作用。在这些研究中,我们试图制定一个大鼠雾化电子烟尼古丁自我给药的方案,以此来更好地理解尼古丁暴露途径对行为和生理功能的不同影响。我们报告了一种新的方法,该方法可以在雄性和雌性大鼠中引发强烈的尼古丁雾化自我给药行为。我们的研究结果表明,5mg/ml 的尼古丁电子烟溶液为雄性和雌性大鼠提供了一致的按压杠杆行为水平。此外,在雄性大鼠中,我们发现这种电子烟尼古丁蒸气引起的血液中尼古丁主要代谢物可替宁水平与静脉内尼古丁自我给药相似。因此,在男性中蒸气暴露期间的呼吸模式导致与静脉内尼古丁自我给药相同的滴定尼古丁摄入量。有趣的是,在女性中发现了不同的效果,在这种情况下,相同的蒸气暴露条件导致与静脉内自我给药相比,蒸气中的可替宁水平降低。最后,尼古丁介导的运动能力差异为电子烟蒸气吸入的生理效应提供了进一步的支持。总之,我们的发现揭示了基于暴露途径的尼古丁摄入的重要性别差异,并且我们进一步建立了大鼠尼古丁蒸气自我给药的方案。