Cui Guang-Fu, Hou Min, Shao Yu-Feng, Chen Hai-Lin, Gao Jin-Xian, Xie Jun-Fan, Chen Yu-Nong, Cong Chao-Yu, Dai Feng-Qiu, Hou Yi-Ping
Departments of Neuroscience, Anatomy, Histology, and Embryology, Key Laboratory of Preclinical Study for New Drugs of Gansu Province, School of Basic Medical Sciences, Lanzhou University, Lanzhou, China.
Department of Anatomy, Gansu University of Traditional Chinese Medicine, Lanzhou, China.
Front Neurol. 2019 Aug 13;10:873. doi: 10.3389/fneur.2019.00873. eCollection 2019.
Sleep-wake development in postnatal rodent life could reflect the brain maturational stages. As the altricial rodents, rats are born in a very undeveloped state. Continuous sleep recording is necessary to study the sleep-wake cycle profiles. However, it is difficult to realize in infant rats since they rely on periodic feeding before weaning and constant warming and appropriate EEG electrodes. We developed a new approach including two types of EEG electrodes and milk-feeding system and temperature-controlled incubator to make continuously polysomnographic (PSG) recording possible. The results showed that there was no evident difference in weight gaining and behaviors between pups fed through the milk-feeding system and warmed with temperature-controlled incubator and those kept with their dam. Evolutional profiles of EEG and electromyogram (EMG) activities across sleep-wake states were achieved perfectly during dark and light period from postnatal day (P) 11 to P75 rats. The ontogenetic features of sleep-wake states displayed that the proportion of rapid eye movement (REM) was 57.0 ± 2.4% and 59.7 ± 1.7% and non-REM (NREM) sleep was 5.2 ± 0.8% and 4.9 ± 0.5% respectively, in dark and light phase at P11, and then REM sleep progressively decreased and NREM sleep increased with age. At P75, REM sleep in dark and light phase respectively, reduced to 6.3 ± 0.6% and 6.9 ± 0.5%, while NREM correspondingly increased to 37.5 ± 2.1% and 58.4 ± 1.7%. Wakefulness from P11 to P75 in dark phase increased from 37.8 ± 2.2% to 56.2 ± 2.6%, but the change in light phase was not obvious. P20 pups began to sleep more in light phase than in dark phase. The episode number of vigilance states progressively decreased with age, while the mean duration of that significantly increased. EEG power spectra in 0.5-4 Hz increased with age accompanied with prolonged duration of cortical slow wave activity. Results also indicated that the dramatic changes of sleep-wake cycle mainly occurred in the first month after birth. The novel approaches used in our study are reliable and valid for continuous PSG recording for infant rats and unravel the ontogenetic features of sleep-wake cycle.
出生后啮齿动物的睡眠-觉醒发育可反映大脑成熟阶段。作为晚成性啮齿动物，大鼠出生时处于非常未发育的状态。持续睡眠记录对于研究睡眠-觉醒周期概况是必要的。然而，在幼鼠中很难实现，因为它们在断奶前依赖定期喂食、持续保暖以及合适的脑电图电极。我们开发了一种新方法，包括两种类型的脑电图电极、喂奶系统和控温培养箱，以使连续多导睡眠图（PSG）记录成为可能。结果表明，通过喂奶系统喂食并在控温培养箱中保暖的幼崽与和母鼠在一起的幼崽在体重增加和行为方面没有明显差异。在出生后第（P）11天到P75天的大鼠的黑暗期和光照期，完美地获得了跨睡眠-觉醒状态的脑电图和肌电图（EMG）活动的发育概况。睡眠-觉醒状态的个体发育特征显示，在P11时，快速眼动（REM）睡眠比例在黑暗期和光照期分别为57.0±2.4%和59.7±1.7%，非快速眼动（NREM）睡眠分别为5.2±0.8%和4.9±0.5%，然后REM睡眠随着年龄增长逐渐减少，NREM睡眠增加。在P75时，黑暗期和光照期的REM睡眠分别降至6.3±0.6%和6.9±0.5%，而NREM睡眠相应增加到37.5±2.1%和58.4±1.7%。从P11到P75，黑暗期的觉醒从37.8±2.2%增加到56.2±2.6%，但光照期的变化不明显。P~20幼崽开始在光照期比黑暗期睡眠更多。警觉状态的发作次数随着年龄增长逐渐减少，而其平均持续时间显著增加。0.5 - 4Hz的脑电图功率谱随着年龄增长而增加，同时伴有皮层慢波活动持续时间延长。结果还表明，睡眠-觉醒周期的显著变化主要发生在出生后的第一个月。我们研究中使用的新方法对于幼鼠连续PSG记录以及揭示睡眠-觉醒周期的个体发育特征是可靠且有效的。
