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症的常见症状，包括严重的抑郁症和创伤后应激障碍(PTSD)。抑郁和创伤后应激障碍与下丘脑-垂体-肾上腺(HPA)轴功能障碍有关。在这些疾病中，大脑中促肾上腺皮质激素释放因子(CRF)的水平长期升高，CRF是HPA轴的关键神经肽调节因子。CRF具有良好的促进觉醒/抑制睡眠的作用。普遍的假设是，CRF诱导的失眠反映了一种高度觉醒的状态，这是由于觉醒增强神经系统的激活，包括下丘脑外侧的下丘脑下丘脑(HCRT)神经元和蓝斑的去甲肾上腺素能神经元。然而，我们有证据表明，中枢应用CRF干扰了位于腹外侧视前区(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一个关键问题：“失眠是否与CRF过度活动有关，是由于过度觉醒，还是睡眠促进回路的缺陷，还是两者兼而有之？”我们提出了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)期间内稳态睡眠需求的变化密切相关。在目标1中，我们将确定视前下丘脑中CRF信号的增加是否会使动态平衡睡眠驱动引起的MnPN和VLPO神经元活动分离。CRF激动剂将通过微透析探针直接输送到MnPN和VLPO中，而单个单位的活动将被记录在紧挨着探针的位置。我们将确定CRF是否抑制SD和RS期间正常增加的MnPN和VLPO神经元放电。在目标1下的第二个实验中，我们将确定局部透析灌流CRF拮抗剂是否能阻止侧脑室(ICV)注射CRF引起的VLPO和MnPN神经元c-fos表达的抑制。目的2将评估中枢CRF给药后激活HCRT神经元在调节睡眠障碍中的功能重要性。我们将确定脑室注射双HCRT受体拮抗剂是否能阻断CRF对SD后RS的抑制。我们还将确定HCRT拮抗剂是否能阻止CRF对MnPN和VLPO神经元c-fos表达的抑制。完成目标1和2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剧暴露在急性社会应激源下的大鼠的睡眠障碍。我们将研究脑室注射CRF对雄性大鼠在急性暴露于雄性同种动物肮脏的床上时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。我们还将比较侧脑室输注CRF拮抗剂和HCRT拮抗剂预防应激性失眠CRF增强的能力。抑郁症和创伤后应激障碍是美国退伍军人中普遍存在的疾病。在这些障碍中管理睡眠障碍是很重要的，因为失眠会加剧抑郁症状，增加焦虑。已有共识认为CRF过度活跃是抑郁症和创伤后应激障碍的重要病理生理学特征。慢性肾功能衰竭改变睡眠的作用是公认的，但潜在的机制尚未解决。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唤醒的现象，这将为情绪和焦虑症中睡眠障碍的药物管理策略提供参考。

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.