Fear Entrainment of Circadian Rhythms

摘要 我们实验室最近的工作表明，周期性恐惧可以通过以下方式战胜昼夜节律的束缚 在夜间活动的啮齿动物中，光-暗(LD)循环并导致白天觅食和摄食。当老鼠或大鼠 被安置在笼子里，它们需要离开安全的筑巢区域才能进入觅食区域 在水中，它们在LD周期的黑暗阶段觅食。如果觅食区域变得危险 在活跃的黑暗阶段，随着随机的脚击，动物的觅食和觅食活动转移到 光相。这种向昼夜行为的切换表示昼夜节律振荡器的输出，该振荡器由 周期性恐惧刺激，依赖于完整的视交叉上核(SCN)，在那里主时钟 和一个完整的杏仁核，它编码恐惧感知。我们对这一提议的工作假设是 杏仁核内的昼夜节律振荡器受到周期性恐惧的影响，并导致 觅食和取食行为。 具体目标1将确定周期性夜间恐惧是否影响杏仁核的昼夜节律振荡器。 和/或在LD或持续黑暗(DD)条件下陷入周期性恐惧的动物的SCN。 具体目标2将确定周期性恐惧是否也会影响觅食和觅食的昼夜节律 在雌性小鼠身上，性别差异是否由卵巢激素调节来解释。 具体目标3将确定是否通过电刺激或光遗传刺激 暗期的杏仁基底外侧核(BLA)足以引起摄食和觅食的夹带， 以及BLA的激活是否是通过光基因抑制恐惧夹带所必需的 动物暴露在恐惧的刺激下。这一目标也将评估体外光遗传刺激是否 杏仁核足以局部包裹杏仁核昼夜节律振荡器。 特定目标4A，B将利用时钟基因BMal1的区域特异性KO或时钟基因的全局KO PER1和PER2来确定哺乳动物的典型分子时钟是否是恐惧诱导的一部分 振荡器。AIM 4C将评估杏仁核特异的BMal1 Kos是否未能引发周期性恐惧。 我们发现夜间恐惧伴随着昼夜节律，这表明编码恐惧的边缘中枢是 协调昼夜节律的回路。它还提供了一个独特的易于处理的系统，以揭示如何 SCN和杏仁核内的主生物钟将光和恐惧信号整合到时间复合体中 行为过程。昼夜节律和睡眠障碍是焦虑和恐惧障碍的标志，如后焦虑和恐惧障碍 创伤性应激障碍；我们的发现可能有助于揭示创伤与创伤之间的神经机制 睡眠和昼夜节律的调节。

SUMMARY Recent work in our laboratory has shown that cyclic fear can prevail over entrainment of circadian rhythms by the light-dark (LD) cycle and lead to diurnal foraging and feeding in nocturnal rodents. When mice or rats are housed in a cage setup in which they need to leave a safe nesting area to access a foraging area for food and water, they forage and feed during the dark phase of the LD cycle. If the foraging area is rendered dangerous with random footshocks during the active dark phase, the animals’ foraging and feeding activity shifts to the light phase. This switch to diurnal behavior represents the output of a circadian oscillator, which is entrained by the cyclic fear stimulus, and is dependent on an intact suprachiasmatic nucleus (SCN), where the master clock resides, and an intact amygdala, which encodes fear perception. Our working hypothesis for this proposal is that a circadian oscillator within the amygdala is entrained by cyclic fear and leads to a shift in the timing of foraging and feeding behavior. Specific Aim 1 will determine whether cyclic nocturnal fear entrains the circadian oscillators in the amygdala and/or the SCN in animals entrained to cyclic fear under LD or constant darkness (DD) conditions. Specific Aim 2 will determine whether cyclic fear can also entrain the circadian rhythms of foraging and feeding in female mice, and whether sex differences are explained by the ovarian hormone regulation. Specific Aim 3 will determine whether the evocation of fear by electrical or optogenetic stimulation of the basolateral amygdala (BLA) during the dark phase is sufficient to induce entrainment of feeding and foraging, and whether the activation of the BLA is necessary for fear entrainment by optogenetically inhibiting it while animals are exposed to the fear stimulus. This Aim will also assess whether in vitro optogenetic stimulation of the amygdala is sufficient to locally entrain the amygdala circadian oscillator. Specific Aim 4A,B will exploit region-specific KOs of the clock gene Bmal1 or global KOs of the clock genes Per1 and Per2 to determine whether canonical molecular clock of mammals is part of the fear-entrained oscillator. Aim 4C will assess whether amygdala-specific Bmal1 KOS fail to entrain to cyclic fear. Our finding that nocturnal fear entrains circadian rhythms indicates that limbic centers that encode fear are part of the circuitry that orchestrates circadian rhythms. It also provides a uniquely tractable system to unmask how the master circadian clock within the SCN and the amygdala integrate photic and fear cues to time complex behavioral processes. Circadian and sleep disorders are a hallmark of anxiety and fear disorders such as post- traumatic stress disorder; our findings could shed light into the neural mechanisms that link trauma to the regulation of sleep and circadian rhythms.