Postprandial sleep mechanics in Drosophila

Abstract

Food consumption is thought to induce sleepiness. However, little is known about how postprandial sleep is regulated. Here, we simultaneously measured sleep and food intake of individual flies and found a transient rise in sleep following meals. Depending on the amount consumed, the effect ranged from slightly arousing to strongly sleep inducing. Postprandial sleep was positively correlated with ingested volume, protein, and salt—but not sucrose—revealing meal property-specific regulation. Silencing of leucokinin receptor (Lkr) neurons specifically reduced sleep induced by protein consumption. Thermogenetic stimulation of leucokinin (Lk) neurons decreased whereas Lk downregulation by RNAi increased postprandial sleep, suggestive of an inhibitory connection in the Lk-Lkr circuit. We further identified a subset of non-leucokininergic cells proximal to Lkr neurons that rhythmically increased postprandial sleep when silenced, suggesting that these cells are cyclically gated inhibitory inputs to Lkr neurons. Together, these findings reveal the dynamic nature of postprandial sleep.DOI: http://dx.doi.org/10.7554/eLife.19334.001

Simultaneous measurement of sleep and feeding in individual Drosophila

“…In various animal models, restricting food intake drives wakefulness 1-3 and manipulating available nutrients modifies sleep on both short and long time scales 4-9 . Beyond the physical act of feeding, changes in energy storage or metabolism stemming from feeding behavior may also be reflected in sleep.…”

“…Previously, use of the ARC was described for measuring the timing and size of discrete feeding events while simultaneously assessing sleep before and after each event. This allowed us to examine the rapid shifts in sleep which result from a meal 4 . The primary advantage of the ARC is the coupling of sleep, arousal, and feeding measurement into a single system to reveal direct behavioral correlates and increase experimental throughput.…”

“…However, individual ARC modules for measuring feeding, sleep, or activity can also be run independently and offer advantages over other independent behavioral measurement systems including ease of chamber customization, increased throughput, and real-time analysis capabilities. Although we previously published an iteration of the ARC that utilized separate cameras and computers for tracking fly movement and food intake 4 , the upgraded system described here uses a single camera per chamber of 30 flies for real-time measurements of both sleep and feeding. A single computer can typically handle two cameras simultaneously for the study of 60 flies in two chambers.…”

“…The system therefore resolves discrete feeding events, facilitating the study of prandial behavior as well as the finer integration of feeding and spatially derived behaviors such as sleep 4 . In the described setup, the ARC makes measurements from 30 individuals per camera, yet data quality is comparable to that from another recently described capillary-based tool, the Expresso, which is also capable of nanoliter resolution 22 .…”

“…The ARC implements object tracking by using JavaGrinders 4 , an open-source, Java-based framework. Acquisition of frames and image operations are performed with OpenCV 25 , a real-time computer vision library.…”