Department of Human Health Science, Tokyo Metropolitan University, 1-1 Minamiohsawa, Hachioji, Tokyo 192-0397, Japan.
Institute of Arts and Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan.
Behav Brain Res. 2023 Jan 5;436:114091. doi: 10.1016/j.bbr.2022.114091. Epub 2022 Sep 1.
As yawning is often observed in stressful or emotional situations such as tension and anxiety, this suggests that yawning can be considered to be an emotional behavior. However, the neural mechanisms underlying emotion-induced yawning remain unclear. It is well known that the hypothalamic paraventricular nucleus (PVN) is the most important brain structure for induction of yawning behavior. We previously showed that induction of yawning involves the central nucleus of the amygdala (CeA), as well as the PVN. Therefore, emotion-induced yawning could potentially be induced through activation of the direct/indirect neural pathways from the CeA to the PVN. Our present study used a combination of retrograde tracing (injection of Fluoro-Gold (FG) into the PVN) and c-Fos immunohistochemistry to examine the neural pathways that evoke emotion-induced yawning. We additionally performed lesion experiments on the CeA using ibotenic acid, a neurotoxin, to determine whether the CeA is involved in the induction of emotion-induced yawning. Emotional stress by fear conditioning induced yawning behavior, and induced expression of double-labeled cells for c-Fos and FG in the bed nucleus of the stria terminalis (BNST), but not in the CeA. Furthermore, the CeA lesions caused by ibotenic acid abolished the induction of emotion-induced yawning. These results suggest that a neural pathway from the CeA to the PVN via the BNST may be primarily involved in the induction of emotion-induced yawning behavior.
由于打哈欠通常发生在紧张和焦虑等压力或情绪状态下，这表明打哈欠可以被视为一种情绪行为。然而，情绪诱导打哈欠的神经机制尚不清楚。众所周知，下丘脑室旁核（PVN）是诱导打哈欠行为的最重要的大脑结构。我们之前的研究表明，打哈欠的诱导涉及杏仁核中央核（CeA）以及 PVN。因此，情绪诱导的打哈欠可能通过激活从 CeA 到 PVN 的直接/间接神经通路来诱导。在本研究中，我们使用逆行示踪（将 Fluoro-Gold（FG）注入 PVN）和 c-Fos 免疫组织化学相结合，研究了诱发情绪诱导打哈欠的神经通路。我们还使用神经毒素 ibotenic acid 对 CeA 进行了损伤实验，以确定 CeA 是否参与了情绪诱导打哈欠的诱导。通过恐惧条件作用引起的情绪应激诱导了打哈欠行为，并诱导了在终纹床核（BNST）中 c-Fos 和 FG 的双标记细胞的表达，但在 CeA 中没有。此外，ibotenic acid 引起的 CeA 损伤消除了情绪诱导打哈欠的诱导。这些结果表明，CeA 到 PVN 的神经通路可能主要通过 BNST 参与情绪诱导打哈欠行为的诱导。
