Grieder Taryn E, George Olivier, Yee Mandy, Bergamini Michael A, Chwalek Michal, Maal-Bared Geith, Vargas-Perez Hector, van der Kooy Derek
Institute of Medical Science, University of Toronto, 1110-160 College St, Toronto, ON, M5S 3E1, Canada.
Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada.
Eur J Neurosci. 2017 Jul;46(1):1673-1681. doi: 10.1111/ejn.13605. Epub 2017 Jun 21.
Nicotine addiction is a worldwide epidemic that claims millions of lives each year. Genetic deletion of α5 nicotinic acetylcholine receptor (nAChR) subunits has been associated with increased nicotine intake, however, it remains unclear whether acute nicotine is less aversive or more rewarding, and whether mice lacking the α5 nAChR subunit can experience withdrawal from chronic nicotine. We used place conditioning and conditioned taste avoidance paradigms to examine the effect of α5 subunit-containing nAChR deletion (α5 -/-) on conditioned approach and avoidance behaviour in nondependent and nicotine-dependent and -withdrawn mice, and compared these motivational effects with those elicited after dopamine receptor antagonism. We show that nondependent α5 -/- mice find low, non-motivational doses of nicotine rewarding, and do not show an aversive conditioned response or taste avoidance to higher aversive doses of nicotine. Furthermore, nicotine-dependent α5 -/- mice do not show a conditioned aversive motivational response to withdrawal from chronic nicotine, although they continue to exhibit a somatic withdrawal syndrome. These effects phenocopy those observed after dopamine receptor antagonism, but are not additive, suggesting that α5 nAChR subunits act in the same pathway as dopamine and are critical for the experience of nicotine's aversive, but not rewarding motivational effects in both a nondependent and nicotine-dependent and -withdrawn motivational state. Genetic deletion of α5 nAChR subunits leads to a behavioural phenotype that exactly matches that observed after antagonizing dopamine receptors, thus we suggest that modulation of nicotinic receptors containing α5 subunits may modify dopaminergic signalling, suggesting novel therapeutic treatments for smoking cessation.
尼古丁成瘾是一种全球性的流行病,每年导致数百万人死亡。α5烟碱型乙酰胆碱受体(nAChR)亚基的基因缺失与尼古丁摄入量增加有关,然而,目前尚不清楚急性尼古丁是否不那么厌恶或更具奖赏性,以及缺乏α5 nAChR亚基的小鼠是否会经历慢性尼古丁戒断。我们使用位置条件反射和条件性味觉回避范式,来研究含α5亚基的nAChR缺失(α5 -/-)对非依赖、尼古丁依赖和戒断小鼠的条件性接近和回避行为的影响,并将这些动机效应与多巴胺受体拮抗后引发的效应进行比较。我们发现,非依赖的α5 -/-小鼠认为低剂量、无动机作用的尼古丁具有奖赏性,并且对较高厌恶剂量的尼古丁不表现出厌恶条件反应或味觉回避。此外,尼古丁依赖的α5 -/-小鼠对慢性尼古丁戒断不表现出条件性厌恶动机反应,尽管它们继续表现出躯体戒断综合征。这些效应与多巴胺受体拮抗后观察到的效应相似,但不具有叠加性,这表明α5 nAChR亚基与多巴胺作用于同一路径,并且对于在非依赖、尼古丁依赖和戒断动机状态下尼古丁的厌恶而非奖赏动机效应的体验至关重要。α5 nAChR亚基的基因缺失导致一种行为表型,与拮抗多巴胺受体后观察到的表型完全匹配,因此我们认为,调节含α5亚基的烟碱型受体可能会改变多巴胺能信号传导,这为戒烟提供了新的治疗方法。