Impact of Corticotropin Releasing Factor (CRF) on Sleep Regulation

描述（由申请人提供）： 失眠和睡眠障碍是情绪和焦虑障碍的常见症状，包括重度抑郁症和创伤后应激障碍（PTSD）。抑郁症和PTSD与下丘脑-垂体-肾上腺（HPA）轴功能障碍有关。促肾上腺皮质激素释放因子（CRF），HPA轴的关键神经肽调节剂，在这些疾病的脑水平长期升高。CRF具有良好的促醒/抑制睡眠作用。流行的假设是CRF诱导的失眠反映了过度觉醒的状态，这是由于唤醒增强神经元系统的激活，包括外侧下丘脑中的下丘脑泌素（HCRT）神经元和蓝斑中的去甲肾上腺素能神经元。然而，我们有证据表明，中央管理的CRF破坏位于腹外侧视前区（VLPO）和正中视前核（MnPN）的关键睡眠调节神经元的活动。本申请中提出的实验解决了关键问题：“失眠是否与由于过度觉醒引起的CRF过度活跃有关，是睡眠促进回路的缺陷，还是两者兼而有之？“我们提出三个目标来回答这个问题。 在之前的资助期间，我们确定了MnPN和VLPO中的神经元放电与睡眠剥夺（SD）和恢复睡眠（RS）期间不断变化的稳态睡眠需求密切相关。在目标1中，我们将确定视前区下丘脑中CRF信号的增加是否使MnPN和VLPO神经元活动与稳态睡眠驱动分离。CRF激动剂将通过微透析探针直接递送到MnPN和VLPO中，同时在紧邻探针处记录单个单位活性。我们将确定CRF是否抑制SD和RS期间发生的MnPN和VLPO神经元放电的正常增加。在目标1下的第二个实验中，我们将确定CRF拮抗剂的局部透析灌注是否阻止由脑室内（ICV）输注CRF诱发的VLPO和MnPN神经元中c-fos表达的抑制。 目的2将评估中枢CRF给药后HCRT神经元激活在介导睡眠障碍中的功能重要性。我们将确定ICV输注双重HCRT受体拮抗剂是否会阻断SD后CRF诱导的RS抑制。我们还将确定HCRT拮抗剂是否阻止对CRF反应中MnPN和VLPO神经元中c-fos表达的抑制。目的1和2的完成应该揭示视前睡眠调节神经元与HCRT神经元作为CRF对睡眠影响的功能靶点的相对重要性。 目的3将确定CRF信号的增加是否会加重暴露于急性社会应激源的大鼠的睡眠障碍。我们将研究CRF ICV给药对雄性大鼠在急性暴露于雄性同种动物污染的垫料期间表现出的失眠程度和持续时间的影响。我们将确定CRF诱导的失眠增强是否伴随着MnPN和VLPO中c-fos表达的抑制。我们还将比较ICV输注CRF拮抗剂和HCRT拮抗剂预防应激性失眠的CRF增强的能力。 抑郁症和PTSD是美国退伍军人中普遍存在的疾病。在这些疾病中管理睡眠障碍很重要，因为失眠会加重抑郁症状并增加焦虑。有共识，CRF多动是抑郁症和PTSD的病理生理学的一个重要特征。CRF的睡眠改变作用已经得到了很好的证实，但其潜在机制尚未得到解决。确定CRF引起的失眠是否反映了睡眠调节回路的中断，或者这种失眠是否纯粹是一种过度觉醒的现象，将为情绪和焦虑障碍中睡眠障碍的药物管理策略提供信息。

DESCRIPTION (provided by applicant): Insomnia and disturbed sleep are common symptoms in mood and anxiety disorders, including major depression and posttraumatic stress disorder (PTSD). Depression and PTSD are associated with dysfunction of the hypothalamic-pituitary-adrenal (HPA) axis. Brain levels of corticotrophin-releasing factor (CRF), a critical neuropeptide regulator of the HPA axis, are chronically elevated in these disorders. CRF has well characterized wake-promoting/sleep-suppressing effects. The prevailing hypothesis is that CRF- induced insomnia reflects a state of hyperarousal, due to activation of wake-enhancing neuronal systems, including hypocretin (HCRT) neurons in the lateral hypothalamus and noradrenergic neurons in the locus coeruleus. However, we have evidence that central administration of CRF disrupts the activity of critical sleep-regulatory neurons located in the ventrolateral preoptic area (VLPO) and median preoptic nucleus (MnPN). Experiments proposed in this application address the critical question: "Is insomnia associated with CRF hyperactivity due to hyperarousal, a deficiency in sleep-promoting circuits, or a combination of both?" We propose three aims to answer this question. During the previous funding period we determined that neuronal discharge in the MnPN and VLPO is tightly coupled to changing homeostatic sleep need during sleep deprivation (SD) and recovery sleep (RS). In Aim 1 we will determine if increased CRF signaling in the preoptic hypothalamus dissociates MnPN and VLPO neuronal activity from homeostatic sleep drive. CRF agonists will be delivered directly into the MnPN and VLPO via a microdialysis probe, while single unit activity is recorded immediately adjacent to the probe. We will determine if CRF suppresses the normal increase in MnPN and VLPO neuronal discharge that occurs during SD and RS. In a second experiment under Aim 1 we will determine if local dialysis perfusion of CRF antagonists prevents the suppression of c-fos expression in VLPO and MnPN neurons that is evoked by intracerebroventricular (ICV) infusion of CRF. Aim 2 will evaluate the functional importance of activation of HCRT neurons in mediating sleep disturbance following central CRF administration. We will determine if ICV infusion of a dual HCRT receptor antagonist will block CRF-induced suppression of RS following SD. We will also determine if HCRT antagonist prevents the suppression c-fos expression in MnPN and VLPO neurons that occurs in response to CRF. Completion of Aims 1 and 2 should reveal the relative importance of preoptic sleep- regulatory neurons versus HCRT neurons as functional targets of CRF effects on sleep. Aim 3 will determine if increased CRF signaling exacerbates sleep disturbance in rats exposed to an acute social stressor. We will examine the effects of ICV administration of CRF on the magnitude and duration of the insomnia that male rats exhibit during acute exposure to the soiled bedding of a male conspecific. We will determine if CRF-induced enhancement of insomnia is accompanied by suppression of c-fos expression in the MnPN and VLPO. We will also compare the ability of ICV infusion of CRF antagonist and HCRT antagonist to prevent the CRF enhancement of stress-induced insomnia. Depression and PTSD are prevalent disorders in U.S. combat Veterans. Managing sleep disturbance in these disorders is important because insomnia can exacerbate depressive symptoms and increase anxiety. There is consensus that CRF hyperactivity is a critical feature of the pathophysiology of depression and PTSD. The sleep altering effects of CRF are well-established, but underlying mechanisms are unresolved. Determining if CRF-induced insomnia reflects disruption of sleep-regulatory circuits, or if this insomnia is purely a phenomenon of hyperarousal will inform strategies for the pharmacological management of sleep disturbance in mood and anxiety disorders.