Department of Physiology, Graduate School of Medical and Dental Sciences, Kagoshima University, 8-35-1 Sakuragaoka, Kagoshima, 890-8544, Japan.
Department of Dental Anesthesiology, Graduate School of Medical and Dental Sciences, Kagoshima University, 8-35-1 Sakuragaoka, Kagoshima, 890-8544, Japan.
Behav Brain Funct. 2021 Apr 26;17(1):3. doi: 10.1186/s12993-021-00176-y.
We had recently reported that linalool odor exposure induced significant analgesic effects in mice and that the effects were disappeared in olfactory-deprived mice in which the olfactory epithelium was damaged, thus indicating that the effects were triggered by chemical senses evoked by linalool odor exposure. However, the peripheral neuronal mechanisms, including linalool receptors that contribute toward triggering the linalool odor-induced analgesia, still remain unexplored. In vitro studies have shown that the transient receptor potential ankyrin 1 (TRPA1) responded to linalool, thus raising the possibility that TRPA1 expressed on the trigeminal nerve terminal detects linalool odor inhaled into the nostril and triggers the analgesic effects. To address this hypothesis, we measured the behavioral pain threshold for noxious mechanical stimulation in TRPA1-deficient mice. In contrast to our expectation, we found a significant increase in the threshold after linalool odor exposure in TRPA1-deficient mice, indicating the analgesic effects of linalool odor even in TRPA1-deficient mice. Furthermore, intranasal application of TRPA1 selective antagonist did not alter the analgesic effect of linalool odor. These results showed that the linalool odor-induced analgesia was triggered by a TRPA1-independent pathway in mice.
我们最近报道称，芳樟醇气味暴露在小鼠中诱导出显著的镇痛效果，而在嗅觉剥夺的小鼠中（嗅觉上皮受损），这种效果消失了，这表明这种效果是由芳樟醇气味暴露引起的化学感觉触发的。然而，外周神经元机制，包括参与触发芳樟醇气味诱导的镇痛作用的芳樟醇受体，仍然未被探索。体外研究表明，瞬时受体电位锚蛋白 1（TRPA1）对芳樟醇有反应，因此，TRPA1 在三叉神经末梢表达的可能性是检测吸入到鼻腔中的芳樟醇气味，并触发镇痛作用。为了验证这一假设，我们测量了 TRPA1 缺陷型小鼠对有害机械刺激的行为疼痛阈值。与我们的预期相反，我们发现在 TRPA1 缺陷型小鼠中，芳樟醇气味暴露后阈值显著增加，这表明即使在 TRPA1 缺陷型小鼠中，芳樟醇气味也具有镇痛作用。此外，TRPA1 选择性拮抗剂的鼻腔内应用并没有改变芳樟醇气味的镇痛作用。这些结果表明，在小鼠中，芳樟醇气味诱导的镇痛作用是由 TRPA1 非依赖性途径触发的。
