Lahmam Mohamed, El M'rabet Abdeslam, Ouarour Ali, Pévet Paul, Challet Etienne, Vuillez Patrick
Faculty of Science, Laboratory of Biology and Health, Abdelmalek Essaâdi University, Tétouan, Morocco.
Chronobiol Int. 2008 Nov;25(6):882-904. doi: 10.1080/07420520802553556.
Wheel-running activity was recorded in Lemniscomys barbarus exposed to different lighting conditions. This rodent shows rhythmic locomotor activity under natural twilight-light/dark (LD) as well as squared-LD cycles. A mean of 77% of the activity occurred during the light phase. Under different controlled photoperiods, the quantity of daily locomotor activity was relatively stable except for a lower level in the shortest photoperiod tested (LD 06:18). The duration of the active phase tended to increase with the duration of the light phase, especially in the longer photoperiods. Whatever the lighting conditions, Lemniscomys barbarus started running before lights-on and stopped after lights-off. The phase angle of activity offset relative to lights-off was stable in each squared-photoperiod, whereas the phase angle of activity onset relative to lights-on was significantly the highest under the shortest photoperiods. Recording of activity under constant lighting conditions showed that the daily rhythm of locomotor activity is fundamentally circadian. The endogenous period was slightly<24 h (mean=23.8 h) in permanent darkness and>24 h (mean=24.5 h) in continuous light. Re-entrainment of the locomotor activity rhythm after a 6 h phase advance or delay requires only four days on average. Moreover, the phase-responses curve to a 30 min light pulse (200 lux) in Lemniscomys barbarus kept in constant dark reveals large phase shifts according to circadian times (CT). With CT0 being defined as the onset of daily activity, maximum phase delay and advance shifts were observed at CT11 (Delta Psi=-5.7 h+/-2.3 h) and CT21 (Delta Psi =4.9+/-1.2 h), respectively. Interestingly, the phase-response curve to light did not show any dead zone. Immunohistochemical staining of the suprachiasmatic nuclei indicates that arginine vasopressin-immunoreactive cell bodies and fibers delimited a dorsal subregion that extends laterally and medially. The ventral subregion is rich in vasoactive intestinal peptide-immunoreactive neurones overlapping a smaller area containing gastrin-releasing peptide-expressing cells and receives numerous fibers labeled with neuropeptide Y antibody. The results of this study clearly demonstrate that Lemniscomys barbarus is a diurnal species highly sensitive to the shifting effects of light. Overall, this rodent can be considered a new and interesting model for circadian rhythm neurobiology.
在暴露于不同光照条件下的巴氏条纹松鼠中记录了转轮活动。这种啮齿动物在自然的晨昏光/暗（LD）以及方形LD周期下表现出有节律的运动活动。平均77%的活动发生在光照阶段。在不同的受控光周期下，每日运动活动量相对稳定，除了在测试的最短光周期（LD 06:18）中较低。活跃阶段的持续时间倾向于随着光照阶段的持续时间增加，尤其是在较长的光周期中。无论光照条件如何，巴氏条纹松鼠在开灯前开始奔跑，在关灯后停止。在每个方形光周期中，活动偏移相对于关灯的相位角是稳定的，而活动开始相对于开灯的相位角在最短光周期下显著最高。在恒定光照条件下记录活动表明，运动活动的每日节律基本上是昼夜节律。在永久黑暗中，内源性周期略小于24小时（平均=23.8小时），在持续光照中大于24小时（平均=24.5小时）。在提前或延迟6小时的相位后，运动活动节律的重新同步平均仅需四天。此外，在持续黑暗中饲养的巴氏条纹松鼠对30分钟光脉冲（200勒克斯）的相位响应曲线根据昼夜时间（CT）显示出大的相位偏移。将CT0定义为每日活动的开始，在CT11（ΔΨ=-5.7小时±2.3小时）和CT21（ΔΨ =4.9±1.2小时）分别观察到最大相位延迟和提前偏移。有趣的是，对光的相位响应曲线没有显示任何死区。视交叉上核的免疫组织化学染色表明，精氨酸加压素免疫反应性细胞体和纤维界定了一个向外侧和内侧延伸的背侧亚区域。腹侧亚区域富含血管活性肠肽免疫反应性神经元，与一个较小的区域重叠，该区域包含表达胃泌素释放肽的细胞，并接收大量用神经肽Y抗体标记的纤维。这项研究的结果清楚地表明，巴氏条纹松鼠是一种对光的变化效应高度敏感的昼行性物种。总体而言，这种啮齿动物可被视为昼夜节律神经生物学的一个新的有趣模型。
