Orexin受体拮抗剂对睡眠剥夺的戊四氮致(癎)大鼠癫(癎)发作及脑组织病理学变化的影响

目的 探讨orexin-1受体(OX1R)和orexin-2受体(OX2R)拮抗剂对睡眠剥夺(SD)的戊四氮(PTZ)致(癎)大鼠癫(癎)发作及脑组织病理学变化的影响.方法 雄性Wistar大鼠48只,随机分为正常对照(NC)组、PTZ组、SD+ PTZ( SD)组、SD+ PTZ+二甲基亚砜(DMSO)组、SD+ PTZ+ OX1R拮抗剂SB334867(SB)组和SD+ PTZ+ OX2R拮抗剂TCS OX229 (TCS)组.采用改良多平台SD法,SD前及SD 48 h分别给予相应组大鼠侧脑室注射DMSO、SB或TCS.SD 72 h给予各组腹腔注射PTZ 50 mg/kg诱导癫(癎)发作;观察各组大鼠癫(癎)发作的潜伏期、发作等级评分、发作持续时间及死亡率;应用常规染色法观察海马的病理学变化,免疫荧光法(BrdU标记)观察神经细胞增殖的变化.结果 (1)与PTZ组比较,SD组及DMSO组(癎)性发作的潜伏期明显缩短,发作等级评分、持续时间及死亡率明显增加(均P ＜0.001),海马CA3区神经元损害加重,海马齿状回门区和颗粒细胞下层BrdU阳性细胞数显著增多(P＜0.001);SD组与DMSO组间差异无统计学意义.(2)与SD组比较,SB组和TCS组大鼠(癎)性发作的潜伏期明显延长,发作等级评分、持续时间及死亡率明显下降(均P＜0.05),海马CA3区神经元损害明显减轻,齿状回门区和颗粒下层BrdU阳性细胞数减少(均P ＜0.05);TCS组的变化较SB组更显著(P＜0.05 ～0.01).结论 Orexin受体拮抗剂尤其是OX2R拮抗剂可通过减轻海马CA3区神经元的损害和抑制齿状回区细胞增殖减轻SD对PTZ诱导癫(癎)发作的不利影响.     

Orexin-1受体拮抗剂对慢性点燃癫大鼠学习记忆的影响及海马神经细胞的增殖变化

目的:研究orexin-1受体(OX1R)拮抗剂(SB334867,SB)对戊四氮(PTZ)慢性点燃癫大鼠空间学习记忆能力及海马齿状回神经细胞增殖的影响。方法:Wistar大鼠随机分为①对照组[腹腔和侧脑室均注射生理盐水(NS)];②PTZ组(腹腔注射PTZ+侧脑室注射NS);③PTZ+orexin-A(OXA)组(腹腔注射PTZ+侧脑室注射OXA);④PTZ+SB组(腹腔注射PTZ+侧脑室注射SB);⑤PTZ+SB+OXA组(腹腔注射PTZ+侧脑室注射SB和OXA)。观察各组大鼠的空间学习记忆能力及海马齿状回区BrdU+和BrdU+/NeuN+细胞的表达。结果:与PTZ+OXA组比较,PTZ+SB+OXA组大鼠逃避潜伏期延长、穿越平台象限的次数减少(P<0.05)。免疫荧光显示,PTZ+OXA组大鼠齿状回区BrdU+和BrdU+/NeuN+细胞表达增多(P<0.01),而PTZ+SB+OXA组大鼠齿状回区BrdU+/NeuN+细胞表达比PTZ+OXA组减少(P<0.01)。结论:OXA通过OX1R能改善癫大鼠的空间学习记忆能力,可能与OX1R介导的海马齿状回神经细胞增殖与分化作用有关。     

戊四氮致疒间大鼠海马S-100 β蛋白变化及其相关性研究

目的探讨戊四氮致疒间大鼠脑内海马区S-100 β蛋白的变化与癫疒间发作持续时间和发作强度之间的关系.方法应用免疫组化法检测惊厥组、癫疒间持续状态组和对照组大鼠海马内S-100 β蛋白阳性细胞数的变化.结果惊厥组大鼠海马内S-100 β蛋白阳性细胞数于致疒间后12 h开始增加,24 h达高峰,72 h恢复,与对照组相比差异有显著性(P<0.01).癫疒间持续状态组大鼠海马内S-100 β蛋白在12 h、24 h均有明显增加,较惊厥组更为显著.两组相比差异有显著性(P<0.01).结论致疒间大鼠海马内S-100 β蛋白阳性细胞数及染色强度与癫疒间持续时间及发作强度有关,提示S-100 β蛋白可作为临床上判断癫疒间后脑损伤、特别是神经胶质细胞损伤的一种较灵敏而特异的指标.     

戊四氮致猫急性癫疒间发作相关脑区锰离子增强功能MRI成像的研究

目的 探讨锰离子(Mn2+)增强功能MRI成像对确定癫疒间发作相关脑区的价值.并进一步确定癫疒间与钙超载的相关性,从而对癫疒间的发病机制和定位进行研究.方法 给成年猫肌肉注射戊四氮(PTZ)制作癫疒间模型,观察猫的行为学和脑电图改变;在癫疒间急性发作时和发作后24 h进行Mn2+ 功能MRI成像检查;对信号明显增强的脑区做病理学检查并与对照组比较.结果 PTZ致疒间猫脑电图呈阵发性高波幅棘-慢波.癫疒间发作组猫Mn2+功能MRI成像显示大脑皮质明显弥漫性增强,其中额、顶、枕叶脑皮质增强率达34.6%,颞叶皮质增强率达约22.9%,与对照组相比差异有极显著性(均P＜0.01).癫疒间发作后24 h组Mn2+功能MRI成像仍显示额、顶叶明显强化.强化区的神经元有明显变性、坏死.结论 额、顶叶为PTZ致疒间猫癫疒间发作形成的相关脑区,Mn2+增强功能MRI成像能显示癫疒间发作的部位,并可进一步揭示癫疒间发病机制.     

氯化锂-匹罗卡品致(疒间)大鼠脑髓鞘转录因子的表达及其意义

目的探讨氯化锂-匹罗卡品致疒间大鼠脑髓鞘转录因子1(MyT1)的表达及其意义.方法给SD大鼠先后腹腔注射氯化锂、匹罗卡品,制成癫疒间动物模型;用免疫荧光组化法检测癫疒间大鼠癫疒间发作后不同时间大脑皮质和海马CA1区MyT1阳性细胞数.结果与对照组相比,癫疒间后1 d组大鼠海马CA1区MyT1阳性细胞数显著减少(P＜0.05),癫疒间后其他各时间组大鼠脑皮质和海马CA1区MyT1阳性细胞数均有明显的增加,其中癫疒间后7 d组MyT1阳性细胞数最多(P＜0.01,P＜0.05).结论氯化锂-匹罗卡品致疒间大鼠早期大脑MyT1表达增加,并有时程性变化.     

雌激素和克罗米酚对致(疒间)大鼠海马γ-氨基丁酸免疫反应细胞和GABAA受体α1亚单位表达的影响

目的了解雌激素和克罗米酚对海人藻酸(KA)致(疒间)大鼠癫(疒间)发作行为学的影响及其影响癫(疒间)活动的部分机制.方法将去势的雌性大鼠添加雌激素(20mg/kg)或添加雌激素和克罗米酚治疗,比较各组大鼠致(疒间)后癫(疒间)发作的行为学变化;并采用间接免疫荧光法检测各组大鼠海马中γ-氨基丁酸(GABA)免疫反应细胞及GABAA受体α1亚单位表达的变化.结果添加雌激素治疗组大鼠癫(疒间)发作的潜伏期和到达4/5级(4级或5级)的时间[分别为(24.63±11.44)min和(41.50±16.22)min]均较去势组[分别为(46.75±14.61)min和(65.13±12.99)min]明显缩短,而同时添加雌激素和克罗米酚治疗组的潜伏期[(43.50±5.75)min]比单纯添加雌激素组明显延长.雌激素组的阳性免疫反应细胞数在大鼠海马的某些区域也较去势组明显减少,克罗米酚组与雌激素组相比则有所增多.结论高水平的雌激素可促进癫(疒间)发作,克罗米酚添加治疗具有一定的抗癫(疒间)作用.这可能与脑内GABA能系统某些功能的改变有关.     

戊四氮致癎大鼠海马S-100β蛋白变化及其相关性研究

目的　探讨戊四氮致疒间 大鼠脑内海马区S 10 0 β蛋白的变化与癫 疒间 发作持续时间和发作强度之间的关系。方法　应用免疫组化法检测惊厥组、癫疒间 持续状态组和对照组大鼠海马内S 10 0 β蛋白阳性细胞数的变化。结果　惊厥组大鼠海马内S 10 0 β蛋白阳性细胞数于致 疒间 后 12h开始增加 ,2 4h达高峰 ,72h恢复 ,与对照组相比差异有显著性 (P <0 0 1)。癫疒间 持续状态组大鼠海马内S 10 0 β蛋白在 12h、2 4h均有明显增加 ,较惊厥组更为显著。两组相比差异有显著性 (P <0 0 1)。结论　致疒间 大鼠海马内S 10 0 β蛋白阳性细胞数及染色强度与癫疒间 持续时间及发作强度有关 ,提示S 10 0 β蛋白可作为临床上判断癫 疒间 后脑损伤、特别是神经胶质细胞损伤的一种较灵敏而特异的指标。     

立体定向方法建立大鼠红藻氨酸颞叶癫疒间模型及其脑电活动的实验研究

目的探讨采用立体定向技术建立大鼠颞叶癫癎模型的方法,并对发作后的脑电活动进行研究。方法用立体定向方法在20只SD大鼠的右侧海马注射红藻氨酸,用视频监测大鼠的行为学变化;在双侧海马、额叶皮质、杏仁核置入深部电极,对大鼠脑电活动进行长期记录。结果根据Racine行为学分级法,Ⅴ级6只,Ⅳ级10只,Ⅲ级3只,Ⅱ级1只;深部电极描记出起源于海马并向额叶皮质、杏仁核等传导癫疒间样波;病理变化提示长期癫疒间发作会导致海马锥体细胞逐渐缺失、坏死。结论用立体定向技术建立大鼠红藻氨酸颞叶癫疒间模型是一种可靠、经济和实用的方法。起源于海马并向额叶皮质、杏仁核等传导的癫疒间样波是颞叶癫疒间模型的神经电生理基础。     

神经颗粒素在海人酸诱发癫(疒间)大鼠皮质及海马中表达的研究

目的探讨海人酸(KA)诱发癫疒间后不同时间大鼠皮质及海马各区神经颗粒素的表达及意义。方法将52只SD大鼠随机分为癫疒间诱发组(KA组)和正常对照组。运用免疫荧光染色共聚焦显微镜观察大鼠制模成功后6 h、12 h、18 h、24 h、48 h 5个时点皮质及海马各区神经颗粒素表达的变化;蛋白质免疫印记(W estern B lot)技术对皮质及海马神经颗粒素作选择性半定量分析,并进行比较。结果与正常对照组相比,KA组制模18 h大鼠皮质神经颗粒素表达开始减少(P<0.05),24 h为最低(P<0.01),48 h恢复正常;制模12 h海马齿状回神经颗粒素明显下降(P<0.05),18 h最低(P<0.01),48 h恢复正常;海马CA1区制模后神经颗粒素持续下降,48 h时与正常对照组比较差异有显著性(P<0.05);CA3区未见显著变化。W estern B lot实验印证了这一结果。结论KA诱发的复杂部分性癫疒间发作急性期能引起大鼠皮质及海马神经颗粒素表达减少,在各脑区的变化不同,且有可恢复的趋势,可能与癫疒间发作后引起大脑神经元突触可塑性改变有关。     

癫癎大鼠海马区白细胞介素1受体1免疫反应阳性细胞的观察

目的:探讨白细胞介素1受体1(IL-1R1)在海马区的表达与癫(疒间)发病的关系。方法:用免疫细胞化学法,观察成年和美解眠致(疒间)大鼠海马区IL-1R1免疫反应(IL-1R1-IR)阳性细胞分布。结果:成年大鼠海马区存在IL-1R1-IR阳性细胞。美解眠致(疒间)后,海马区该阳性细胞数显著增多(P＜0.01);致(疒间)前后给予尼莫地平,海马区该阳性细胞均较癫(疒间)大鼠显著减少(P＜0.01),与正常比较无显著差异(P＞0.05)。结论:海马区IL-1R1参与癫(疒间)的病理过程,其机制可能与其介导该区细胞内信号传导有关。尼莫地平不仅可以阻止癫(疒间)发作,而且可以减轻其继发的脑损伤。     

Pentylenetetrazol-induced seizures are exacerbated by sleep deprivation through orexin receptor-mediated hippocampal cell proliferation

Sleep deprivation has been shown to be an activator of seizures in clinical and animal studies. Orexin-A was speculated to be involved in the aggravation of seizures by sleep deprivation through the activation of its receptors: orexin-1 and orexin-2 receptor (OX1R and OX2R, respectively). Therefore, we aimed to investigate the effects of pre-treating sleep-deprived Wistar rats with the OX1R or OX2R antagonists, SB334867 (30 nM/kg) or TCS OX2 29 (30 nM/kg), respectively, followed by a convulsive dose of 50 mg/kg pentylenetetrazol administration (seizure induction), on seizure behavior, and hippocampal neurodegeneration and cellular proliferation. Our results revealed that treatment with SB334867 or TCS OX2 29 significantly prolonged the latency and reduced the duration of seizures, while also lowering the mortality rate in sleep-deprived rats exposed to pentylenetetrazol. In addition, SB334867 or TCS OX2 29 reduced the damage to hippocampal CA3 neurons and the number of bromodeoxyuridine-positive cells in the dentate gyrus (particularly in the hilus). Overall, the effect of TCS OX2 29 was greater than that of SB334867. Taken together, these data suggest that OX1R and OX2R antagonists may alleviate the damage of pentylenetetrazol-induced seizures that are exacerbated by sleep deprivation, and furthermore could be associated with a reduction of neuronal damage in the hippocampus and the inhibition of cellular proliferation in the dentate gyrus.     

Role of orexin receptors in the ventral tegmental area on acquisition and expression of morphine-induced conditioned place preference in the rats

The orexins are hypothalamic neuropeptides and their role in reward processing and drug addiction has been demonstrated. The extent of involvement of each orexin receptor in the acquisition and expression of conditioned place preference (CPP) for morphine is still a matter of controversy. We investigated the functional differences between orexin-1 and -2 receptor blockade in the ventral tegmental area (VTA) on the acquisition and expression of morphine CPP. A total of 86 adult male Wistar rats weighing 250 ± 30 g (age 7–8 weeks) received intra-VTA microinjection of either SB334867 (0.1, 1 and 10 nM), a selective orexin-1 receptor (OX1R) antagonist, or TCS-OX2-29 (1, 5 and 25 nM), a selective orexin-2 receptor (OX2R) antagonist. To measure the acquisition, the animals received each antagonist (SB334867 or TCS-OX2-29) 5 min prior to subcutaneous injection of morphine (5 mg/kg) during the conditioning phase. To measure the CPP expression, the animals received each antagonist on the post-conditioning phase. The CPP conditioning score was recorded by Ethovision software. Data showed that intra-VTA microinjection of OX1-R antagonist significantly attenuated morphine CPP acquisition, during the conditioning phase, and expression, during the post-conditioning phase. Intra-VTA microinjection of OX2-R antagonist also significantly attenuated morphine CPP acquisition and expression in the mentioned phases. Our results showed the orexin role in learning and memory and indicate that orexin receptors (OX1R and OX2R) function in the VTA is essential for both acquisition and expression of morphine reward in rats in the CPP model.     

The arousal effect of hyperbaric oxygen through orexin/hypocretin an upregulation on ketamine/ethanol-induced unconsciousness in male rats

Approaches that facilitate the recovery from coma would have enormous impacts on patient outcomes and medical economics. Orexin-producing neurons release orexins (also known as hypocretins) energy-dependently to maintain arousal. Hyperbaric oxygen (HBO) could increase ATP levels by preserving mitochondrial function. We investigated, for the first time, the arousal effects of HBO and orexins mechanisms in a rat model of unconsciousness induced by ketamine or ethanol. A total of 120 Sprague-Dawley male rats were used in this study. Unconsciousness was induced either by intraperitoneal injection of ketamine or ethanol. The HBO treatment (100% O2 at 3 ATA) was administered immediately after unconsciousness induction for 1 hr. SB334867, orexin-1 receptor (OX1R) inhibitor, or JNJ10397049, orexin-2 receptor (OX2R) inhibitor was administered 30 min intraperitoneally before unconsciousness induction. Loss of righting reflex test (LORR) and Garcia test were used to evaluate the unconsciousness duration and neurological deficits after recovering from unconsciousness, respectively. Enzyme-linked immunosorbent assay was used to measure brain tissue ATP and orexin A levels. Ketamine or ethanol injection resulted in LORR immediately and neurological deficits 6 hr after unconsciousness induction. HBO treatment significantly reduced the LORR duration, improved Garcia scores and unregulated ATP and orexin A levels in the brain tissue. Administration of OX1R inhibitor or OX2 R inhibitor abolished arousal and neurological benefits of HBO. In conclusion, HBO exerted arousal-promoting effects on unconscious rats induced by ketamine or ethanol. The underlying mechanism was via, at least in part, ATP/orexin A upregulation. HBO may be a practical clinical approach to accelerate unconsciousness recovery in patients.     

Wake-promoting effects of vagus nerve stimulation after traumatic brain injury: upregulation of orexin-A and orexin receptor type 1 expression in the prefrontal cortex

Orexins, produced in the lateral hypothalamus, are important neuropeptides that participate in the sleep/wake cycle, and their expression coincides with the projection area of the vagus nerve in the brain. Vagus nerve stimulation has been shown to decrease the amounts of daytime sleep and rapid eye movement in epilepsy patients with traumatic brain injury. In the present study, we investigated whether vagus nerve stimulation promotes wakefulness and affects orexin expression. A rat model of traumatic brain injury was established using the free fall drop method. In the stimulated group, rats with traumatic brain injury received vagus nerve stimulation(frequency, 30 Hz; current, 1.0 mA; pulse width, 0.5 ms; total stimulation time, 15 minutes). In the antagonist group, rats with traumatic brain injury were intracerebroventricularly injected with the orexin receptor type 1(OX1R) antagonist SB334867 and received vagus nerve stimulation. Changes in consciousness were observed after stimulation in each group. Enzyme-linked immunosorbent assay, western blot assay and immunohistochemistry were used to assess the levels of orexin-A and OX1R expression in the prefrontal cortex. In the stimulated group, consciousness was substantially improved, orexin-A protein expression gradually increased within 24 hours after injury and OX1R expression reached a peak at 12 hours, compared with rats subjected to traumatic brain injury only. In the antagonist group, the wake-promoting effect of vagus nerve stimulation was diminished, and orexin-A and OX1 R expression were decreased, compared with that of the stimulated group. Taken together, our findings suggest that vagus nerve stimulation promotes the recovery of consciousness in comatose rats after traumatic brain injury. The upregulation of orexin-A and OX1R expression in the prefrontal cortex might be involved in the wake-promoting effects of vagus nerve stimulation.     

Role of the Ventromedial Hypothalamic Orexin-1 Receptors in Regulation of Gastric Acid Secretion in Conscious Rats

Orexins play an important role on the central nervous system to modulate gastric acid secretion. The orexin receptors are distributed within the hypothalamus, and expression of orexin-1 receptors (OX1R) is greatest in the anterior hypothalamus and ventromedial nucleus. Therefore, we hypothesised that ventromedial hypothalamic OX1R may be involved in the control of gastric acid secretion. To address this question, we examined the effects of orexin-A and a selective OX1R antagonist, SB-3345867, on gastric acid secretion in pyloric-ligated conscious rats. Intraventromedial injection of orexin-A (0.5–2 μg/μl) stimulated gastric acid secretion in a dose-dependent manner. This stimulatory effect of orexin-A persisted over 3 h. In some experiments, SB-3345867 (10 mg/kg i.p.) was administered 30 min before orexin-A or saline injections. We found that i.p. injection of SB-334867 suppressed stimulated gastric acid secretion induced by orexin-A (2 μg/μl). Atropine (5 mg/kg) also inhibited the stimulatory effect of central injection of orexin-A on acid secretion. In conclusion, the present study suggests that endogenous orexin-A acts on the ventromedial hypothalamus to stimulates acid secretion. This stimulatory effect is probably mediated through OX1R.     

雷帕霉素对未成年癫痫模型大鼠的毒性作用

目的利用戊四氮(pentylenetetrazol,PTZ)慢性点燃Sprague Dawley大鼠(SD大鼠)模型观察在点燃初期腹腔注射雷帕霉素(rapamycin,RAPA)能否抑制癫痫发生以及雷帕霉素在治疗中的安全性。方法将6~8周龄SD雄性大鼠随机分为雷帕霉素干预组PTZ+RAPA及其对照组PTZ+NS(normal saline)及NS组,观察1周(w)、2周(w)、4周(w)、6周(w)共4个时间点,每亚组12只,观察实验动物体质量的变化、死亡率及癫痫发作情况。结果各组实验大鼠的死亡率:PTZ+RAPA组为22.9%,PTZ+NS组为10.4%,NS组为0%。PTZ+RAPA组与PTZ+NS组各个相对应的时间点(1 w,2 w,4 w,6 w)体质量差均有统计学差异(P0.001)。6周时PTZ+RAPA组的点燃率为66.7%,PTZ+NS组的点燃率为58.3%,二者无统计学差异(P0.05)。PTZ+RAPA组与PTZ+NS组相对应时间点(1 w,2 w,4 w,6 w)发作分值的两两比较差异无统计学意义(P0.05)。结论雷帕霉素未能减少或抑制未成年大鼠的癫痫发作,但能明显降低未成年SD大鼠的体质量,可能有一定的毒副作用。     

Resuscitation therapy for traumatic brain injuryinduced coma in rats:mechanisms of median nerve electrical stimulation

In this study, rats were put into traumatic brain injury-induced coma and treated with median nerve electrical stimulation. We explored the wake-promoting effect, and possible mechanisms, of median nerve electrical stimulation. Electrical stimulation upregulated the expression levels of orexin-A and its receptor OX1 R in the rat prefrontal cortex. Orexin-A expression gradually increased with increasing stimulation, while OX1 R expression reached a peak at 12 hours and then decreased. In addition, after the OX1 R antagonist, SB334867, was injected into the brain of rats after traumatic brain injury, fewer rats were restored to consciousness, and orexin-A and OXIR expression in the prefrontal cortex was downregulated. Our findings indicate that median nerve electrical stimulation induced an up-regulation of orexin-A and OX1 R expression in the prefrontal cortex of traumatic brain injury-induced coma rats, which may be a potential mechanism involved in the wake-promoting effects of median nerve electrical stimulation.     

Orexin‐1 receptor signaling increases motivation for cocaine‐associated cues

The orexin/hypocretin system is involved in multiple cocaine addiction processes that involve drug‐associated environmental cues, including cue‐induced reinstatement of extinguished cocaine seeking and expression of conditioned place preference. However, the orexin system does not play a role in several behaviors that are less cue‐dependent, such as cocaine‐primed reinstatement of extinguished cocaine seeking and low‐effort cocaine self‐administration. We hypothesized that cocaine‐associated cues, but not cocaine alone, engage signaling at orexin‐1 receptors (OX1Rs), and this cue‐engaged OX1R signaling increases motivation for cocaine. Motivation for cocaine was measured in Sprague–Dawley rats with behavioral‐economic demand curve analysis after pretreatment with the OX1R antagonist SB‐334867 (SB) or vehicle with and without light + tone cues. Demand for cocaine was higher when cocaine‐associated cues were present, and SB only reduced cocaine demand in the presence of these cues. We then investigated whether cocaine demand was linked to the cued reinstatement of cocaine seeking, as both procedures are partially driven by cocaine‐associated cues in an orexin‐dependent manner. SB blocked cue‐induced reinstatement behavior, and baseline demand predicted SB efficacy with the largest effect in high‐demand animals, i.e. animals with the greatest cue‐dependent behavior. We conclude that OX1R signaling increases the reinforcing efficacy of cocaine‐associated cues but not that of cocaine alone. This supports our view that orexin plays a prominent role in the ability of conditioned cues to activate motivational responses.     

Opposite effects of sleep rebound on orexin OX1 and OX2 receptor expression in rat brain

Orexins (hypocretins) have been implicated in the regulation of the normal sleep-wake cycle, in sensorimotor programming, and in other homeostatic and neuroregulatory processes. The present study examined the effects of sleep deprivation (SD) and sleep recovery on the expression of orexin 1 receptors (OX1R) and orexin 2 receptors (OX2R) throughout the brain. Rats were sacrificed either immediately after 96 h of sleep deprivation (SD group) or after SD followed by 24 h of sleep recovery (Rebound group). Prepro-orexin mRNA showed a non-significant increase in the SD group relative to controls, but a pronounced and significant increase in the Rebound group (+88%, P < 0.007). Similarly, sleep deprivation produced no effect on OX1R or OX2R mRNA levels. However, in the Rebound group, OX1R mRNA levels increased significantly, compared to either control or SD groups, in 37 of 92 brain regions analyzed, with particularly strong effects in the amygdala and hypothalamus. Changes in OX2R mRNA levels were also seen only in the sleep Rebound group, but they were fewer in number (10 out of 86 regions), were in the direction of decreased rather than increased expression, and were predominantly confined to cerebral cortical areas. These observations indicate that some factor associated with sleep recovery, possibly the compensatory increase in REM sleep, has strong effects on the orexin system at the mRNA level. They further indicate that,pOX1 and OX2 receptors are affected in opposite way and that the former are more vulnerable to these effects than the latter.