Department of Physics, James Franck Institute, University of Chicago, Chicago, IL 60637, USA.
Sleep. 2013 Mar 1;36(3):385-95. doi: 10.5665/sleep.2456.
The nematode C. elegans develops through four larval stages before it reaches adulthood. At the transition between stages and before it sheds its cuticle, it exhibits a sleep-like behavior during a stage termed lethargus. The objectives of this study were to characterize in detail behavioral patterns and physiological activity of a command interneuron during lethargus.
We found that lethargus behavior was composed of bouts of quiescence and motion. The duration of individual bouts ranged from 2 to 100 seconds, and their dynamics exhibited local homeostasis: the duration of bouts of quiescence positively correlated with the duration of bouts of motion that immediately preceded them in a cAMP-dependent manner. In addition, we identified a characteristic body posture during lethargus: the average curvature along the body of L4 lethargus larvae was lower than that of L4 larvae prior to lethargus, and the positions of body bends were distributed non-uniformly along the bodies of quiescent animals. Finally, we found that the AVA interneurons, a pair of backward command neurons, mediated locomotion patterns during L4 lethargus in similar fashion to their function in L4 larvae prior to lethargus. Interestingly, in both developmental stages backward locomotion was initiated and terminated asymmetrically with respect to AVA intraneuronal calcium concentration.
The complex behavioral patterns during lethargus can be dissected to quantifiable elements, which exhibit rich temporal dynamics and are actively regulated by the nervous system. Our findings support the identification of lethargus as a sleep-like state.
Iwanir S; Tramm N; Nagy S; Wright C; Ish D; Biron D. The microarchitecture of C. elegans behavior during lethargus: homeostatic bout dynamics, a typical body posture, and regulation by a central neuron. SLEEP 2013;36(3):385-395.
线虫 C. elegans 在发育为成虫之前要经历四个幼虫阶段。在阶段之间的过渡时期，也就是在蜕皮之前，它会在一个称为昏睡的阶段表现出类似睡眠的行为。本研究的目的是详细描述一个命令中间神经元在昏睡期间的行为模式和生理活动。
我们发现，昏睡行为由静止和运动的爆发组成。单个爆发的持续时间从 2 秒到 100 秒不等，它们的动态表现出局部的稳态：静止爆发的持续时间与它们之前的运动爆发的持续时间呈正相关，这是一种 cAMP 依赖性的关系。此外，我们在昏睡期间发现了一种特征性的身体姿势：L4 昏睡幼虫的平均曲率比昏睡前的 L4 幼虫低，身体弯曲的位置在静止动物的身体上呈非均匀分布。最后，我们发现 AVA 中间神经元，一对向后的命令神经元，以类似于其在 L4 幼虫之前的功能的方式介导 L4 昏睡期间的运动模式。有趣的是，在这两个发育阶段，向后运动都是不对称地启动和终止的，与 AVA 神经元内钙浓度有关。
昏睡期间复杂的行为模式可以分解为可量化的元素，这些元素表现出丰富的时间动态，并受到神经系统的主动调节。我们的研究结果支持将昏睡识别为一种类似睡眠的状态。
