title: Serotonin modulates locomotory behavior and coordinates egg-laying and movement in Caenorhabditis elegans.
abstract: Biogenic amines have been implicated in the modulation of neural circuits involved in diverse behaviors in a wide variety of organisms. In the nematode C. elegans, serotonin has been shown to modulate the temporal pattern of egg-laying behavior. Here we show that serotonergic neurotransmission is also required for modulation of the timing of behavioral events associated with locomotion and for coordinating locomotive behavior with egg-laying. Using an automated tracking system to record locomotory behavior over long time periods, we determined that both the direction and velocity of movement fluctuate in a stochastic pattern in wild-type worms. During periods of active egg-laying, the patterns of reversals and velocity were altered: velocity increased transiently before egg-laying events, while reversals increased in frequency following egg-laying events. The temporal coordination between egg-laying and locomotion was dependent on the serotonergic HSN egg-laying motorneurons as well as the decision-making AVF interneurons, which receive synaptic input from the HSNs. Serotonin-deficient mutants also failed to coordinate egg-laying and locomotion and exhibited an abnormally low overall reversal frequency. Thus, serotonin appears to function specifically to facilitate increased locomotion during periods of active egg-laying, and to function generally to modulate decision-making neurons that promote forward movement.
authors.affiliation: Division of Biology, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0349, USA.
authors.forename: L A
authors.initials: LA
authors.lastname: Hardaker
authors.forename: E
authors.initials: E
authors.lastname: Singer
authors.forename: R
authors.initials: R
authors.lastname: Kerr
authors.forename: G
authors.initials: G
authors.lastname: Zhou
authors.forename: W R
authors.initials: WR
authors.lastname: Schafer
mesh_terms: D000465:Algorithms; D000818:Animals; D017173:Caenorhabditis elegans / Q000502:physiology*; D005260:Female; D007395:Interneurons / Q000502:physiology; D009043:Motor Activity / Q000502:physiology*; D009046:Motor Neurons / Q000502:physiology; D009474:Neurons / Q000502:physiology; D010058:Oviposition; D012701:Serotonin / Q000502:physiology*
chemical_list: D012701:Serotonin