Department of Psychology, Program in Neuroscience, Florida State University, Tallahassee, FL, United States of America.
PLoS One. 2024 Feb 23;19(2):e0298448. doi: 10.1371/journal.pone.0298448. eCollection 2024.
Monoterpenes are a large class of naturally occurring fragrant molecules. These chemicals are commonly used in olfactory studies to survey neural activity and probe the behavioral limits of odor discrimination. Monoterpenes (typically in the form of essential oils) have been used for centuries for therapeutic purposes and have pivotal roles in various biological and medical applications. Despite their importance for multiple lines of research using rodent models and the role of the olfactory system in detecting these volatile chemicals, the murine sensitivity to monoterpenes remains mostly unexplored. We assayed the ability of C57BL/6J mice to detect nine different monoterpenes (the acyclic monoterpenes: geraniol, citral, and linalool; the monocyclic monoterpenes: r-limonene, s-limonene, and γ-terpinene; and the bicyclic monoterpenes: eucalyptol, α-pinene, and β-pinene) using a head-fixed Go / No-Go operant conditioning assay. We found that mice can reliably detect monoterpene concentrations in the low parts per billion (ppb) range. Specifically, mice were most sensitive to geraniol (threshold: 0.7 ppb) and least sensitive to γ-terpinene (threshold: 18.1 ppb). These estimations of sensitivity serve to set the lower limit of relevant monoterpene concentrations for functional experiments in mice. To define an upper limit, we estimated the maximum concentrations that a mouse may experience in nature by collating published headspace analyses of monoterpene concentrations emitted from natural sources. We found that natural monoterpenes concentrations typically ranged from ~1 to 1000 ppb. It is our hope that this dataset will help researchers use appropriate monoterpene concentrations for functional studies and provide context for the vapor-phase delivery of these chemicals in studies investigating their biological activity in mice.
单萜是一大类天然存在的具有香味的分子。这些化学物质通常用于嗅觉研究，以调查神经活动并探测气味辨别能力的行为极限。单萜（通常以精油的形式）已被用于治疗用途数百年，并在各种生物和医学应用中起着关键作用。尽管它们对使用啮齿动物模型进行的多条研究线很重要，并且嗅觉系统在检测这些挥发性化学物质方面起着重要作用，但鼠类对单萜的敏感性在很大程度上仍未得到探索。我们使用头部固定的 Go / No-Go 操作性条件反射测定法来测定 C57BL/6J 小鼠检测九种不同单萜（无环单萜：香叶醇、柠檬醛和芳樟醇；单环单萜：r-柠檬烯、s-柠檬烯和γ-萜品烯；双环单萜：桉叶醇、α-蒎烯和β-蒎烯）的能力。我们发现，小鼠可以可靠地检测到低部分每十亿（ppb）范围内的单萜浓度。具体来说，小鼠对香叶醇（阈值：0.7 ppb）最敏感，对γ-萜品烯（阈值：18.1 ppb）最不敏感。这些敏感性估计值为小鼠体内功能实验设定了相关单萜浓度的下限。为了定义上限，我们通过整理已发表的天然来源释放的单萜浓度的顶空分析，估算了小鼠在自然界中可能经历的最大浓度。我们发现，天然单萜浓度通常在 1 到 1000 ppb 之间。我们希望该数据集将帮助研究人员在功能研究中使用适当的单萜浓度，并为研究这些化学物质在小鼠中的生物活性时在气相中输送这些化学物质提供背景信息。
