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. 2012 Jan 1;1(1):12-4.
doi: 10.4161/worm.19499.

Reduced muscle contraction and a relaxed posture during sleep-like Lethargus

Juliane Schwarz  1 , Jan-Philipp Spies, Henrik Bringmann
Affiliations

Reduced muscle contraction and a relaxed posture during sleep-like Lethargus

Juliane Schwarz et al. Worm. .

Abstract

Sleep is characterized by reduced muscle activity resulting in reduced movement and a typical posture compatible with relaxed muscles. Prior to each molt, C. elegans larvae go through a phase of behavioral quiescence called Lethargus. Lethargus has sleep-like properties, but a specific posture has not yet been described. Do C. elegans larvae relax their muscles during sleep and do they assume a typical posture? We measured worm posture and body wall muscle activity using calcium imaging across the sleep-wake-like cycle. We found that worms were less curved and had less muscle activity during the sleep-like state. We conclude that during Lethargus, muscle activity is reduced, resulting in a relaxed body posture typical for a sleep-like state.

Keywords: GCaMP; Lethargus; calcium; muscle; posture; sleep.

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Figures

Figure 1.
Figure 1.
Reduced movement, body curvature, and muscle activity during sleep-like Lethargus. (A) Time-lapse images showing the microcompartment including the entire worm during wake-like state (top) and sleep-like state (bottom). The bright signal is derived from the body wall muscle and reflects calcium intensities. (B) Motility is reduced during C. elegans sleep-like state. We measured averaged nose speed. (C) Reduced curvature during C. elegans sleep-like state. We measured angle change along the long axis of the worm. (D) Reduced muscle activity during C. elegans sleep-like state. We measured GCaMP3.35 intensity. Error bars are SEM n = 15 worms. In the plots, wake-like state is colored red and sleep-like state is colored blue. Individual worms were aligned by the start of Lethargus as defined by cessation of pumping.
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