title: The G-protein-coupled serotonin receptor SER-1 regulates egg laying and male mating behaviors in Caenorhabditis elegans.
abstract: Serotonin (5-HT) is a neuromodulator that regulates many aspects of animal behavior, including mood, aggression, sex drive, and sleep. In vertebrates, most of the behavioral effects of 5-HT appear to be mediated by G-protein-coupled receptors (GPCRs). Here, we show that SER-1 is the 5-HT GPCR responsible for the stimulatory effects of exogenous 5-HT in two sexually dimorphic behaviors of Caenorhabditis elegans, egg laying and male ventral tail curling. Loss of ser-1 function leads to decreased egg laying in hermaphrodites and defects in the turning step of mating behavior in males. ser-1 is expressed in muscles that are postsynaptic to serotonergic neurons and are known to be required for these behaviors. Analysis of the ser-1 mutant also reveals an inhibitory effect of 5-HT on egg laying that is normally masked by SER-1-dependent stimulation. This inhibition of egg laying requires MOD-1, a 5-HT-gated chloride channel. Loss of mod-1 function in males also produces defects in ventral tail curling and enhances the turning defects in ser-1 mutant males. Sustained elevations in 5-HT levels result in behavioral adaptation to both the stimulatory and inhibitory actions of the neurotransmitter, indicating that both SER-1 and MOD-1 signaling can be modulated. Removal of wild-type animals from high levels of exogenous 5-HT produces a SER-1-dependent withdrawal response in which egg laying is significantly decreased. These studies provide insight into the role of 5-HT in behavior and the regulation of 5-HT(2) receptor function.
authors.affiliation: Ernest Gallo Clinic and Research Center, Department of Neurology, Programs in Neuroscience and Biomedical Science, University of California, San Francisco, Emeryville, California 94608, USA.
authors.forename: Lucinda
authors.initials: L
authors.lastname: Carnell
authors.forename: Julie
authors.initials: J
authors.lastname: Illi
authors.forename: Swung Woo
authors.initials: SW
authors.lastname: Hong
authors.forename: Steven L
authors.initials: SL
authors.lastname: McIntire
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000502:physiology*; D029742:Caenorhabditis elegans Proteins / Q000502:physiology*; D005260:Female; D008297:Male; D010058:Oviposition / Q000187:drug effects / Q000502:physiology*; D043562:Receptors, G-Protein-Coupled / Q000819:agonists / Q000502:physiology*; D044263:Receptors, Serotonin, 5-HT1 / Q000502:physiology*; D012701:Serotonin / Q000494:pharmacology; D058825:Serotonin 5-HT1 Receptor Agonists; D012726:Sexual Behavior, Animal / Q000187:drug effects / Q000502:physiology*; D015053:Zygote / Q000187:drug effects / Q000502:physiology
chemical_list: D029742:Caenorhabditis elegans Proteins; D043562:Receptors, G-Protein-Coupled; D044263:Receptors, Serotonin, 5-HT1; D058825:Serotonin 5-HT1 Receptor Agonists; D012701:Serotonin