Department of Neuroscience and Institute of Behavioral Medicine Research, Wexner Medical Center at The Ohio State University, Columbus, USA.
Chronobiol Int. 2012 Jul;29(6):683-92. doi: 10.3109/07420528.2012.682682.
Sleep is regulated by circadian and homeostatic processes, but can be altered by infectious disease. During infection or exposure to inflammatory stimuli, such as bacterial lipopolysaccharide (LPS), the duration and intensity of non-rapid eye movement sleep (NREMS), as measured by electoencephalogram (EEG) delta waves (.5-4 Hz), increase. These sleep alterations are hypothesized to conserve or redirect energy for immune system activation. Many vertebrates exhibit seasonal changes in immune function and sleep-wake cycle, and photoperiod (day length) serves as a reliable environmental cue. For example, winter is energetically demanding for most animals, and Siberian hamsters (Phodopus sungorus) adapted to short winter day lengths display reduced fever after LPS administration to presumably conserve energy. We hypothesized that short days increase the duration and intensity of NREMS after LPS challenge to create additional energy savings, despite evidence to the contrary that high fever is associated with increased NREMS. Male hamsters were housed under long (16 h light (L):8 h dark (D)) or short (8L:16D) day lengths, and chronically implanted with transmitters that recorded EEG and electromyogram (EMG) biopotentials simultaneously or core body temperature. After >10 wks in photoperiod conditions, hamsters received an i.p. injection of LPS or saline (control), and vigilance states (duration and distribution of NREMS, rapid eye movement sleep (REMS), and wakefulness) and EEG delta power spectra (NREMS intensity) were assessed. As expected, LPS treatment increased the duration and intensity of NREMS compared to controls. Hamsters adapted to short photoperiods exhibited cumulatively larger increases in NREMS duration and EEG delta wave amplitude 0-8 h after LPS injection compared to long-day LPS-treated hamsters despite short-day attenuation of fever. These results suggest a seasonal decoupling of LPS-induced fever with sleep to promote energy conservation during predictable energy shortages. Ultimately, the combination of increased sleep and reduced fever could represent a suite of physiological adaptations that increase the probability of surviving winter.
睡眠受昼夜节律和生理稳态过程的调节，但也会受到传染病的影响。在感染或接触到炎症刺激物（如细菌脂多糖（LPS））时，非快速眼动睡眠（NREMS）的持续时间和强度会增加，这可以通过脑电图（EEG）中的 delta 波（0.5-4Hz）来测量。这些睡眠变化被认为是为了为免疫系统的激活节省或重新分配能量。许多脊椎动物的免疫功能和睡眠-觉醒周期会发生季节性变化，光周期（日照时间）是一种可靠的环境线索。例如，冬季对大多数动物来说都是能量消耗大的季节，适应短日照长度的西伯利亚仓鼠（Phodopus sungorus）在注射 LPS 后会出现体温降低，这可能是为了节省能量。我们假设，尽管有相反的证据表明高热与增加的 NREMS 有关，但短日照会增加 LPS 挑战后的 NREMS 持续时间和强度，从而创造额外的能量节省。雄性仓鼠被安置在长光照（16 小时光照（L）：8 小时黑暗（D））或短光照（8L：16D）条件下，并长期植入记录脑电图（EEG）和肌电图（EMG）生物电位的发射器或核心体温。在光照条件下>10 周后，仓鼠接受 LPS 或生理盐水（对照）的腹腔注射，评估警觉状态（NREMS、快速眼动睡眠（REMS）和觉醒的持续时间和分布）和 EEG 德尔塔功率谱（NREMS 强度）。正如预期的那样，与对照组相比，LPS 处理增加了 NREMS 的持续时间和强度。与长光照 LPS 处理的仓鼠相比，适应短光照的仓鼠在 LPS 注射后 0-8 小时内，NREMS 持续时间和 EEG 德尔塔波幅度的累积增加更大，尽管短光照会降低发热。这些结果表明，在可预测的能量短缺期间，LPS 诱导的发热与睡眠的季节性脱耦可以促进能量的节省。最终，增加的睡眠和降低的发热可能代表一系列生理适应，增加了在冬季生存的可能性。
