睡眠剥夺通过影响大鼠下丘脑组蛋白乙酰化调控神经元Orexin A的表达

目的:探讨睡眠剥夺(sleep deprivation,SD)对大鼠下丘脑组蛋白乙酰化水平的影响,并观察乙酰化修饰是否影响神经元下丘脑促觉醒肽Orexin A的表达。方法:成年雄性大鼠24只,采用改良多平台睡眠剥夺法建立大鼠SD模型,随机分为对照组(n=6)和SD组(n=18);Western Blot法检测大鼠下丘脑组蛋白乙酰化水平的变化;免疫荧光法观察下丘脑Orexin A神经元。结果:与对照组相比,SD后1 d,3 d及6 d,下丘脑组蛋白H3亚基9位赖氨酸(H3K9)、H3K14位点的乙酰化水平明显下降(P0.05),但三个时间点之间无显著差异(P0.05)。SD后3 d,下丘脑的Orexin A+神经元数目和对照组相比明显减少(P0.05),而给予组蛋白去乙酰化酶抑制剂SAHA(25 mg/kg,i.p.)可部分恢复SD减少的Orexin A~+神经元数(P0.05)。结论:睡眠剥夺可能通过影响大鼠下丘脑组蛋白的乙酰化修饰水平减少神经元Orexin A的表达。     

低压低氧对大鼠下丘脑Orexin A表达及舌下神经放电的影响

目的:观察慢性间歇性低压低氧(chronic intermittent hypobaric hypoxia,CIHH)模型大鼠下丘脑OrexinA表达及舌下神经放电活动,探讨CIHH对呼吸活动调节的机制。方法:对正常成年雄性SD大鼠进行每天6 h的低压低氧处理,28 d后进行血气分析,采用免疫组织化学染色方法观察大鼠下丘脑Orexin A的表达,记录舌下神经放电作为观察呼吸活动的指标。结果:血气分析显示模型组大鼠的PO2下降,PCO2明显升高(P<0.05,n=6);模型组大鼠下丘脑Orexin A免疫阳性神经元的相对光密度值显著升高(P<0.01,n=5);舌下神经放电幅度积分面积减小(P<0.01,n=6),呼吸频率降低(P<0.05,n=6)。结论:CIHH使大鼠动脉血PO2下降、PCO2明显升高,舌下神经放电活动减弱。下丘脑Orexin A神经元表达的增加提示Orexin的确参与了对呼吸活动的调节,尤其在CIHH时发挥了重要作用。     

REM期睡眠剥夺对大鼠不同脑区组蛋白H3K9和H3K4甲基化水平的影响

目的:研究REM期睡眠剥夺对成年大鼠不同脑区包括海马、腹内侧前额叶皮质、下丘脑和中缝核群的组蛋白H3K9和H3K4三甲基化水平的影响。方法:将成年SD大鼠随机分为正常对照组(con)、睡眠剥夺1 d组(SD1 d)、睡眠剥夺3 d组(SD3 d)、睡眠剥夺6 d组(SD6 d)。采用改良式多平台水环境法建立REM期睡眠剥夺模型,分别于睡眠剥夺后1、3、6 d断头取脑,用免疫荧光染色与Western Blot检测大鼠海马、腹内侧前额叶皮质、下丘脑和中缝核群H3K9和H3K4三甲基化水平的变化,最终结果进行统计学分析。结果:Western Blot结果显示:(1)海马、腹内侧前额叶皮质三个SD组H3K9三甲基化水平均低于control组(P0.05),H3K4三甲基化水平均高于control组(P0.05);(2)下丘脑三个SD组H3K9三甲基化水平均低于control组(P0.01),但SD1 d组H3K4三甲基化水平高于control组(P0.05),SD3 d、SD6 d组H3K4三甲基化水平低于control组(P0.05);(3)中缝核群三个SD组H3K9和H3K4三甲基化水平均高于control组(P0.05)。对海马与下丘脑免疫荧光验证H3K9三甲基化结果与Western Blot结果趋势一致,且说明细胞无减少。结论:睡眠剥夺可能与海马、腹内侧前额叶皮质、下丘脑和中缝核群的组蛋白H3K9和H3K4三甲基化水平密切相关。     

睡眠剥夺后大鼠皮质、海马和杏仁核微管相关蛋白-2及神经丝蛋白的表达变化

目的探讨睡眠剥夺后大鼠皮质、海马和杏仁核微管相关蛋白-2(MAP-2)及神经丝蛋白(NF-200)表达的变化。方法采用改良小平台水环境法制作大鼠睡眠剥夺模型,大鼠随机分为睡眠剥夺组(SD组)、环境对照组(TC组)和空白对照组(CC组)。SD组包括睡眠剥夺6h、12h、1d、2d、3d、5d、7d共7个时点,每个时间点5只大鼠,CC组5只。免疫组织化学法观察MAP-2和NF-200阳性表达。结果睡眠剥夺5d和7d时,皮质、CA1、CA2、CA3、齿状回和杏仁核MAP-2和NF-200阳性表达减少(P0.05,P0.01)。结论睡眠剥夺可导致脑组织MAP-2和NF-200表达减少。     

牛磺酸锌对睡眠剥夺大鼠脑认知功能的影响及机理

目的:探索补锌对睡眠剥夺(SD)后大鼠脑认知功能的影响及机制。方法:采用小平台水环境法制作大鼠SD模型,3天后通过Y-型迷宫行为测试结合NADPH-d组化与免疫组化ABC法,分别观察大鼠海马结构不同亚区内一氧化氮合酶(NOS)活性与神经元型一氧化氮合酶(nNOS)蛋白表达水平的变化。结果:SD组大鼠迷宫实验学会次数(89.3±25.3)较正常对照组大鼠(67.1±29.3)增加(t=1.81,P<0.05),补牛磺酸锌(5.9g/kg饲料牛磺酸锌水平)组大鼠的迷宫实验学会次数(71.9±21.4)较SD组减少(t=1.66,P<0.05)。与正常对照组大鼠海马结构的NOS(CA1:32.6±2.1;CA3:20.5±1.8;DG:27.5±1.8)活性和nNOS蛋白(CA1:68.3±4.1;CA3:41.7±2.5;DG:44.4±2.8)表达相比,SD组大鼠海马结构各亚区NOS(CA1:14.8±1.2;CA3:10.6±1.0;DG:13.1±1.3)活性和CA1区与齿状回nNOS蛋白(CA1:51.3±3.6;DG:41.6±2.7)表达减少(P<0.05),CA3区nNOS蛋白变化不明显(38.1±4.8,P>0.05)。与SD组大鼠相比,补牛磺酸锌组大鼠海马结构不同亚区内的NOS表达增加(CA1:27.2±2.8;CA3:15.3±1.6;DG:21.8±1.9,P<0.05),CA1区的nNOS蛋白表达增加(60.1±3.4,P<0.05),CA3和齿状回nNOS表达变化不明显(CA3:39.6±4.9;DG:42.8±3.5,P>0.05)。结论:牛磺酸锌对大鼠学习记忆功能有促进作用,其机理可能与上调海马结构NOS、nNOS表达水平有关。     

Fmr1基因在大鼠快速眼动睡眠剥夺后脑皮质、海马和丘脑区的表达

目的探讨快速眼动(REM)睡眠剥夺过程中Fmr1基因在大鼠皮质、海马和丘脑区的表达及变化。方法采用改良多平台水环境法(MMPM)制作大鼠睡眠剥夺模型,采用免疫组织化学法及RT-PCR方法检测Fmr1基因的表达变化。结果在皮质和丘脑中,与CC组和TC组相比,SD1d和SD2d组的Fmr1基因表达无明显变化,SD3d组开始增高(P0.05),SD5d、SD7d组和SD9d组显著增高(P0.01);在海马中,与CC组和TC组相比,SD1d和SD2d组的Fmr1基因表达无明显变化,SD3d组开始降低(P0.05),SD5d、SD7d组和SD9d组显著降低(P0.01)。结论 Fmr1基因在大鼠睡眠剥夺第3天开始表达发生变化,在皮质和丘脑中表达增高,在海马中表达降低。     

可卡因戒断对大鼠睡眠结构和脑电功率谱的影响

目的: 探索可卡因戒断对睡眠觉醒活动的影响。方法: 大鼠体内植入无线发射器,用药前、停药第1 d(急性)、8 d(亚急性)、14 d(亚慢性)记录自由活动大鼠脑电波24 h。结果: 停药第1 d睡眠觉醒周期上升(P<0.05)。停药第8 d夜晚和白天,非快动眼睡眠(NREM)增加(P<0.05),快动眼睡眠(REM)下降(P<0.01);停药第14 d,NREM睡眠夜晚显著增加(P<0.01)而白天仅略加强,白天和夜间REM睡眠均明显下降(P<0.01)。停药期间白天和夜间总睡眠无明显变化。整个实验期间,NREM、REM睡眠和觉醒状态的δ、θ 和α脑电功率谱均无显著变化。结论: 可卡因戒断所致睡眠障碍主要由于快、慢波睡眠间而非睡眠与觉醒间异动。急性戒断造成睡眠觉醒间转换异常,而睡眠结构失调则发生在亚急性和亚慢性戒断期间。     

人参皂甙对大鼠自发睡眠结构的影响机制

 摘要：目的 研究人参皂甙（GS）调节自然睡眠的作用机制。方法 雄性SD大鼠随机分为对照、GS低(10 mg/kg)和高（100 mg/kg）剂量组。在大鼠体内植入无线发射器,术后按10和100mg/ kg GS或蒸馏水每日1次给大鼠灌胃,共6天。第1（急性）和6天（慢性）给药后,开始记录自由活动大鼠脑电活动12 h。在并列进行的另一个实验中,于大鼠给药第1和6天用乙醚麻醉后断头处死,取下丘脑组织检测GABAAergic系统蛋白表达情况。结果 GS 灌胃第1天,低剂量GS略微（P?>0.05）而高剂量显著增加非快动眼睡眠（NREM）和总睡眠而减少觉醒时间（P? <0.05）; 与对照组相比,GS低和高剂量均未改变大鼠下丘脑GAD蛋白表达（P? >0.05）,但都增强了GABAA受体α、?亚型而没有影响?亚型表达（P? <0.05）。连续灌胃第6天,低、高剂量GS均显著增加NREM和总睡眠,减少觉醒（P? <0.05）;同时低剂量GS略微上调低剂量GS略微（P?>0.05）而高剂量GS显著增强大鼠下丘脑GAD蛋白表达水平（P? <0.05）,但低、高剂量GS均未能影响GABAA受体表达（P? >0.05）。结论 GS能时间和剂量依赖性地调节大鼠的自然睡眠结构,其急性作用可能与下丘脑增加的GABAA受体α、?亚型蛋白表达有关,而慢性作用可能涉及经由上调GAD表达水平增加GABA产量。     

右美托咪定对快速眼动睡眠剥夺大鼠学习记忆障碍的影响

目的:探讨右美托咪定对快速眼动(REM)睡眠剥夺大鼠学习记忆障碍的影响。方法:将64只健康雄性SD大鼠随机分为对照组(control)、快速眼动睡眠剥夺组(RSD)、右美托咪定组(DEX)和右美托咪定干预的快速眼动睡眠剥夺组(RSD+DEX)。每组16只。应用改良多平台水环境法建立大鼠快速眼动睡眠剥夺模型,通过腹腔内注射给予大鼠右美托咪定,采用Morris水迷宫检测大鼠空间学习记忆能力,采用尼氏染色法检测大鼠海马神经元形态学改变,同时应用试剂盒检测大鼠海马组织匀浆中丙二醛(MDA)含量及超氧化物歧化酶(SOD)活性。结果:与RSD组大鼠相比,RSD+DEX组大鼠逃避成功潜伏期趋于缩短(P 0. 05),穿越平台次数与目标象限时间百分比均明显增加(均P 0. 05),MDA含量减少,SOD活性均增加(P 0. 05),海马CA1区神经元排列较规则,尼氏小体明显增加。结论:右美托咪定能够改善REM睡眠剥夺大鼠学习记忆损伤,这可能与右美托咪定缓解REM睡眠剥夺大鼠海马神经细胞氧化应激和恢复受损细胞有关。     

快速眼动睡眠剥夺对中枢5-羟色胺缺失小鼠orexin阳性神经元活性的影响

为探讨中枢5羟色胺(5-HT)的缺失对正常睡眠和快速眼动睡眠剥夺(REM sleep deprivation)情况下orexin阳性神经元活动的影响,本研究利用中枢5-HT神经元缺失的条件性基因敲除小鼠(Pet1-Cre/Lmx1b flox/flox CKO小鼠),采用小平台水环境法建立小鼠快速眼动睡眠剥夺模型,免疫组化方法观察野生型小鼠和中枢5-HT神经元缺失小鼠在正常睡眠状态及8 h快速眼动睡眠剥夺后下丘脑内orexin阳性神经元的数量,免疫组化双标法观察orexin/c-fos双标神经元占orexin阳性神经元的比例。结果显示:CKO小鼠睡眠剥夺前后orexin阳性神经元的数量未见明显差别,与野生型小鼠相比亦未见统计学差别;在正常睡眠状态下(对照组),CKO小鼠orexin/c-fos双标神经元的数量与野生型小鼠相当,但睡眠剥夺后明显低于野生型小鼠睡眠剥夺组。本研究结果提示,作为维持觉醒的重要神经递质5-HT的缺失可能降低了中枢神经系统的觉醒水平,致使睡眠剥夺不能提高促发和维持觉醒的orexin阳性神经元的活性。     

Rapid eye movement sleep deprivation contributes to reduction of neurogenesis in the hippocampal dentate gyrus of the adult rat

Study Objectives:

The dentate gyrus (DG) of the adult hippocampus contains progenitor cells, which have potential to differentiate into neurons. Previously we reported that 96 hours of total sleep deprivation reduces neurogenesis in the DG of adult rats. Loss of either non-rapid eye movement (NREM) or rapid eye movement (REM) sleep could have contributed to the effect of total sleep deprivation. The present study assessed the effect of 4 days of REM sleep deprivation (REMD) on neurogenesis.

Design:

REMD was achieved by brief treadmill movement initiated by automatic online detection of REM sleep. A yoked-control (YC) rat was placed in the same treadmill and experienced the identical movement regardless the stage of the sleep-wake cycle. The thymidine analog 5- bromo- 2′- deoxy-uridine and the intrinsic proliferation marker, Ki-67, were both used to label proliferating cells.

Setting:

Basic neurophysiology laboratory.

Participants:

Male Sprague-Dawley male rats (300 – 320 g)

Results:

REM sleep was reduced by 85% in REMD rats and by 43% in YC, compared with cage control animals and by 79% in REMD rats compared with YC. NREM sleep and slow wave activity within NREM did not differ in REMD and YC groups. Cell proliferation was reduced by 63 % in REMD compared with YC rats, and by 82% and 51%, respectively, in REMD and YC rats compared with cage controls. Across all animals, cell proliferation exhibited a positive correlation with the percentage of REM sleep (r = 0.84, P < 0.001). Reduced cell proliferation in REMD rats was confirmed with the intrinsic proliferation marker, Ki-67. REMD also reduced the percentage of proliferating cells that later expressed a mature neuronal marker.

Conclusions:

The present findings support a hypothesis that REM sleep-associated processes facilitate proliferation of granule cells in the adult hippocampal DG.

Citation:

Guzman-Marin R; Suntsova N; Bashir T; Nienhuis R; Szymusiak R; McGinty D. Rapid eye movement sleep deprivation contributes to reduction of neurogenesis in the hippocampal dentate gyrus of the adult rat. SLEEP 2008;31(2):167–175.     

Adenosine and the homeostatic control of sleep: effects of A1 receptor blockade in the perifornical lateral hypothalamus on sleep-wakefulness

The orexinergic neurons of the lateral hypothalamus (LH) are critical for wakefulness [McCarley RW (2007) Neurobiology of REM and NREM sleep. Sleep Med 8:302-330]. Recent evidence suggests that adenosine (AD), a homeostatic sleep factor, may act via A1 receptor (A1R) to control orexinergic activity and regulate sleep-wakefulness [Thakkar MM, Winston S, McCarley RW (2002) Orexin neurons of the hypothalamus express adenosine A1 receptors. Brain Res 944:190-194; Liu ZW, Gao XB (2006) Adenosine inhibits activity of hypocretin/orexin neurons via A1 receptor in the lateral hypothalamus: a possible sleep-promoting effect. J Neurophysiol]. To evaluate the role of AD in the orexinergic LH and its influences on sleep-wakefulness, we designed two experiments in freely behaving rats: First, we bilaterally microinjected 1,3-dipropyl-8-phenylxanthine (DPX) (1.5 pmol and 15 pmol), a selective A1R antagonist into the LH during the light cycle and examined its effect on spontaneous sleep-wakefulness. Second, we performed 6 h of sleep deprivation. Thirty minutes before the animals were allowed to enter recovery sleep, 15 pmol of DPX was bilaterally microinjected into the LH and its effects on recovery sleep were monitored. Microinjection of DPX into the orexinergic LH produced a significant increase in wakefulness with a concomitant reduction in sleep, both during spontaneous bouts of sleep-wakefulness and during recovery sleep. Local administration of DPX into the LH produced a significant increase in the latency to non-REM sleep during recovery sleep. However, total slow wave (delta) activity during non-REM sleep phase of recovery sleep remained unaffected after DPX treatment. This is the first study that implicates endogenous adenosine to have a functional role in controlling orexinergic tone and influencing the homeostatic regulation of sleep-wakefulness.     

青春期大鼠癫痫发作后海马齿状回颗粒细胞层神经细胞增殖的改变

目的:探讨青春期大鼠癫痫发作后海马齿状回颗粒细胞层神经细胞数量的变化。方法:选择健康4周龄雄性SD大鼠,应用氯化锂-匹罗卡品药物点燃造模,造模成功后根据取脑组织时间分为24 h组、2周组、4周组,并设相应的对照组。溴脱氧尿嘧啶核苷(BrdU)标记后免疫荧光染色,用激光共聚焦观察大鼠海马齿状回(DG)颗粒细胞层BrdU阳性细胞。结果:24 h和2周实验组BrdU阳性细胞显著增多,分别较对照组增加55.1%和39.6%,2周实验组比24 h实验组降低15.5%(P<0.05);4周实验组BrdU阳性细胞数较对照组无明显差异(P>0.05)。结论:青春期大鼠癫痫发作可引起海马齿状回颗粒层神经细胞增殖的升高,但随着时间的延长有下降的趋势,至4周左右神经细胞的增殖趋于正常。     

Increased apoptosis in rat brain after rapid eye movement sleep loss

Rapid eye movement (REM) sleep loss impairs several physiological, behavioral and cellular processes; however, the mechanism of action was unknown. To understand the effects of REM sleep deprivation on neuronal damage and apoptosis, studies were conducted using multiple apoptosis markers in control and experimental rat brain neurons located in areas either related to or unrelated to REM sleep regulation. Furthermore, the effects of REM sleep deprivation were also studied on neuronal cytoskeletal proteins, actin and tubulin. It was observed that after REM sleep deprivation a significantly increased number of neurons in the rat brain were positive to apoptotic markers, which however, tended to recover after the rats were allowed to undergo REM sleep; the control rats were not affected. Further, it was also observed that REM sleep deprivation decreased amounts of actin and tubulin in neurons confirming our previous reports of changes in neuronal size and shape after such deprivation. These findings suggest that one of the possible functions of REM sleep is to protect neurons from damage and apoptosis.     

Orexin Neurons Are Necessary for the Circadian Control of REM Sleep

Study Objectives:

The orexin-producing neurons are hypothesized to be essential for the circadian control of sleep/wake behavior, but it remains unknown whether these rhythms are mediated by the orexin peptides or by other signaling molecules released by these neurons such as glutamate or dynorphin. To determine the roles of these neurotransmitters, we examined the circadian rhythms of sleep/wake behavior in mice lacking the orexin neurons (ataxin-3 [Atx] mice) and mice lacking just the orexin neuropeptides (orexin knockout [KO] mice).

Design:

We instrumented mice for recordings of sleep-wake behavior, locomotor activity (LMA), and body temperature (T_b) and recorded behavior after 6 days in constant darkness.

Results:

The amplitude of the rapid eye movement (REM) sleep rhythm was substantially reduced in Atx mice but preserved in orexin KO mice. This blunted rhythm in Atx mice was caused by an increase in the amount of REM sleep during the subjective night (active period) due to more transitions into REM sleep and longer REM sleep episodes. In contrast, the circadian variations of T_b, LMA, Wake, non-REM sleep, and cataplexy were normal, suggesting that the circadian timekeeping system and other output pathways are intact in both Atx and KO mice.

Conclusions:

These results indicate that the orexin neurons are necessary for the circadian suppression of REM sleep. Blunting of the REM sleep rhythm in Atx mice but not in orexin KO mice suggests that other signaling molecules such as dynorphin or glutamate may act in concert with orexins to suppress REM sleep during the active period.

Citation:

Kantor S; Mochizuki T; Janisiewicz AM; Clark E; Nishino S; Scammell TE. Orexin neurons are necessary for the circadian control of REM sleep. SLEEP 2009;32(9):1127-1134.     

Potential role of the cannabinoid receptor CB1 in rapid eye movement sleep rebound

Sleep is an unavoidable activity of the brain. The delay of the time to sleep (sleep deprivation), induces an increase of slow-wave sleep and rapid-eye-movement (REM) sleep (rebound) once the subject is allowed to sleep. This drive to sleep has been hypothesized to be dependent on the accumulation of sleep-inducing molecules and on the high expression of these molecule receptors. In this study we selectively deprived rats of REM sleep for 24 h by using the flowerpot technique. One group deprived of REM sleep was treated with SR141716A, a cannabinoid receptor 1 (CB1) receptor antagonist and then allowed to sleep for the next 4 h. Two other groups were killed, one immediately after the REM sleep deprivation period and the other after 2 h of REM sleep rebound (REM sleep deprivation plus 2 h of rebound). In both groups we determined the expression of the CB1 receptor and its mRNA. Results indicated that SR141716A prevents REM sleep rebound and REM sleep deprivation does not modify the expression of the CB1 protein or mRNA. However, REM sleep deprivation plus 2 h of sleep rebound increased the CB1 receptor protein and, slightly but significantly, decreased mRNA expression. These results suggest that endocannabinoids may be participating in the expression of REM sleep rebound.     

Dopamine Transporter Regulation during Four Nights of REM Sleep Deprivation Followed by Recovery – An in vivo Molecular Imaging Study in Humans

Objectives:

To assess the influence of total or selective REM sleep deprivation on the dopamine transporter (DAT) densities and sleep patterns of healthy volunteers.

Design:

Prospective study.

Setting:

Evaluation of polysomnography recordings and DAT density after 4 nights of selective REM sleep deprivation followed by 3 nights of sleep recovery compared to a control group and a group that was subjected to 2 nights of total sleep deprivation. Single positron emission computed tomography and [^99mTc]TRODAT-1 were used to assess the cerebral DAT density in the striatum at baseline, after REM sleep deprivation and total sleep deprivation as well as after sleep recovery. Blood was collected daily to examine prolactin and estradiol levels, which were correlated with dopaminergic activity.

Patients or Participants:

Thirty healthy male volunteers ranging from 19 to 29 years of age were randomly assigned to one of three experimental groups after giving written informed consent (10 non-sleep deprived, 10 total sleep deprived, and 10 REM sleep deprived).

Measurements and Results:

Four nights of REM sleep deprivation and 2 nights of total sleep deprivation induced distinct and heterogeneous patterns of sleep recovery. No significant modulation of DAT availability was observed within groups. In the recovery nights, changes in cortisol, prolactin and estradiol concentrations were significantly correlated with specific sleep stages in the total and REM sleep deprived groups. In addition, DAT density was positively correlated with estradiol concentration and inversely associated with SWS latency only after total sleep deprivation.

Conclusion:

Our study demonstrates that although sleep deprivation did not promote significant alterations in DAT density within the striatum, there were significant correlations among transporter availability, hormonal concentrations and sleep parameters.

Citation:

Martins, RCS; Andersen ML; Garbuio SA; Bittencourt LR: Guindalini C; Shih MC; Hoexter MQ; Bressan RA; Castiglioni MLV; Tufik S. Dopamine transporter regulation during four nights of REM sleep deprivation followed by recovery – an in vivo molecular imaging study in humans. SLEEP 2010;33(2):243-251.     

Modafinil, d-amphetamine and placebo during 64 hours of sustained mental work. II. Effects on two nights of recovery sleep

Polysomnograms were obtained from 37 volunteers, before (baseline) and after (two consecutive recovery nights) a 64-h sleep deprivation, with (d-amphetamine or modafinil) or without (placebo) alerting substances. The drugs were administered at 23.00 hours during the first sleep deprivation night (after 17.5 h of wakefulness), to determine whether decrements in cognitive performance would be prevented; at 05.30 hours during the second night of sleep deprivation (after 47.5 h of wakefulness), to see whether performance would be restored; and at 15.30 hours during the third day of continuous work, to study effects on recovery sleep. The second recovery night served to verify whether drug-induced sleep disturbances on the first recovery night would carry over to a second night of sleep. Recovery sleep for the placebo group was as expected: the debt in slow-wave sleep (SWS) and REM sleep was paid back during the first recovery night, the rebound in SWS occurring mainly during the first half of the night, and that of REM sleep being distributed evenly across REM sleep episodes. Recovery sleep for the amphetamine group was also consistent with previously published work: increased sleep latency and intrasleep wakefulness, decreased total sleep time and sleep efficiency, alterations in stage shifts, Stage 1, Stage 2 and SWS, and decreased REM sleep with a longer REM sleep latency. For this group, REM sleep rebound was observed only during the second recovery night. Results for the modafinil group exhibited decreased time in bed and sleep period time, suggesting a reduced requirement for recovery sleep than for the other two groups. This group showed fewer disturbances during the first recovery night than the amphetamine group. In particular, there was no REM sleep deficit, with longer REM sleep episodes and a shorter REM latency, and the REM sleep rebound was limited to the first REM sleep episode. The difference with the amphetamine group was also marked by less NREM sleep and Stage 2 and more SWS episodes. No REM sleep rebound occurred during the second recovery night, which barely differed from placebo. Hence, modafinil allowed for sleep to occur, displayed sleep patterns close to that of the placebo group, and decreased the need for a long recovery sleep usually taken to compensate for the lost sleep due to total sleep deprivation.