Ferry Barbara
Centre of Research in Neuroscience Lyon, CNRS UMR 5292 - INSERM U1028 UCBL1 Lyon, France.
Front Behav Neurosci. 2014 May 6;8:164. doi: 10.3389/fnbeh.2014.00164. eCollection 2014.
A large variety of behaviors that are essential for animal survival depend on the perception and processing of surrounding smells present in the natural environment. In particular, food-search behavior, which is conditioned by hunger, is directly driven by the perception of odors associated with food, and feeding status modulates olfactory sensitivity. The orexinergic hypothalamic peptide orexin A (OXA), one of the central and peripheral hormones that triggers food intake, has been shown to increase olfactory sensitivity in various experimental conditions including the conditioned odor aversion learning paradigm (COA). COA is an associative task that corresponds to the association between an olfactory conditioned stimulus (CS) and a delayed gastric malaise. Previous studies have shown that this association is formed only if the delay separating the CS presentation from the malaise is short, suggesting that the memory trace of the odor is relatively unstable. To test the selectivity of the OXA system in olfactory sensitivity, a recent study compared the effects of fasting and of central infusion of OXA during the acquisition of COA. Results showed that the increased olfactory sensitivity induced by fasting and by OXA infusion was accompanied by enhanced COA learning performances. In reference to the duration of action of OXA, the present work details the results obtained during the successive COA extinction tests and suggests a hypothesis concerning the role of the OXA component of fasting on the memory processes underlying CS-malaise association during COA. Moreover, referring to previous data in the literature we suggest a functional circuit model where fasting modulates olfactory memory processes through direct and/or indirect activation of particular OXA brain targets including the olfactory bulb, the locus coeruleus (LC) and the amygdala.
动物生存所必需的各种各样的行为都依赖于对自然环境中周围气味的感知和处理。特别是，受饥饿制约的食物搜索行为直接由与食物相关的气味感知驱动，而进食状态会调节嗅觉敏感性。食欲素能下丘脑肽食欲素A（OXA）是触发食物摄入的中枢和外周激素之一，已被证明在包括条件性气味厌恶学习范式（COA）在内的各种实验条件下会增加嗅觉敏感性。COA是一种关联任务，对应于嗅觉条件刺激（CS）与延迟性胃部不适之间的关联。先前的研究表明，只有当CS呈现与不适之间的延迟较短时，这种关联才会形成，这表明气味的记忆痕迹相对不稳定。为了测试OXA系统在嗅觉敏感性方面的选择性，最近的一项研究比较了禁食和在COA习得过程中中枢注射OXA的效果。结果表明，禁食和注射OXA所诱导的嗅觉敏感性增加伴随着COA学习表现的增强。参照OXA的作用持续时间，本研究详细阐述了在连续的COA消退测试中获得的结果，并提出了一个关于禁食中的OXA成分在COA期间CS-不适关联的记忆过程中所起作用的假设。此外，参照文献中的先前数据，我们提出了一个功能回路模型，其中禁食通过直接和/或间接激活包括嗅球、蓝斑（LC）和杏仁核在内的特定OXA脑靶点来调节嗅觉记忆过程。
