Satiated animals stop eating and often fall asleep. Previously we reported a new behavior, satiety quiescence, in worms which mimics the satiety behavior in mammals [1]. To date the behavior has been evaluated by eye and only at specific refeeding time points to not disturb worms. We have therefore been limited in investigating the time course of the behavior or whether certain behavioral states are ruled by changes in nutritional status during refeeding. In fact, several works analyzing worm locomotion have identified two states of locomotion, roaming and dwelling, affected by nutritional state and sensory perception [2,3]. This suggests locomotive activity can be readout of animals' nutritional states. However, satiety quiescence has not been identified using locomotive activity. We have developed an automated, quantitative, and unbiased system to monitor worm locomotive activity to identify satiety quiescence in addition to previously characterized roaming and dwelling behaviors. With our system, we found long periods of little or no movement after starvation and refeeding, distinct from dwelling, consistent with the previous method to evaluate quiescence. As with satiety quiescence, this inactivity state is dependent on nutritional status and food quality; worms are active on poor quality food but are inactive in high quality food. Worms that have experienced starvation show more pronounced and longer inactivity than worms that have not experienced starvation. Moreover, mutants of insulin, cGMP, and TGF-b signaling pathways that are known to regulate satiety quiescence lack this prolonged inactivity. We identify this inactivity in locomotion as satiety quiescence and provide a new and easy method to evaluate and analyze satiety quiescence. We are currently generating a mathematical model based on this data using a Hidden Markov Model to address whether there are specific patterns of activity and if so whether those patterns are cyclic. 1.You, Y.J., et al., Insulin, cGMP, and TGF-beta signals regulate food intake and quiescence in C. elegans: a model for satiety. Cell Metab, 2008. 7(3): p. 249-57. 2.Ben Arous, et al., Molecular and Sensory Basis of a Food Related Two-State Behavior in C. elegans. PLoS ONE, 2009. 4(10): e7584. 3. Fujiwara, et al., Regulation of Body Size and Behavioral State of C. elegans by Sensory Perception and the EGL-4 cGMP-Dependent Protein Kinase. Neuron, 2003. 36(6): 1091-102.

Affiliation:
- Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, VA.