The serotonin receptor SER-1 (5HT2ce) contributes to the regulation of locomotion in Caenorhabditis elegans.
Serotonin (5-hydroxytryptamine: 5HT) is an important neuroactive substance in the model roundworm, Caenorhabditis elegans. Aside from having effects in feeding and egg-laying, 5HT inhibits motility and also modulates several locomotory behaviors, notably food-induced slowing and foraging. Recent evidence showed that a serotonergic 5HT2-like receptor named SER-1 (also known as 5HT2ce) was responsible for the effect of 5HT on egg-laying. Here we confirm this observation and show that SER-1 also plays an important role in locomotion. A mutant lacking SER-1 was found to be highly resistant to exogenous 5HT in the absence of food and this resistant phenotype was rescued by reintroducing the SER-1 gene in a mutant background. Pharmacological studies showed that the same antagonists that blocked the activity of recombinant SER-1 in vitro also inhibited the effect of 5HT on motility, suggesting the same receptor was responsible for both effects. When tested for locomotory behaviors, the SER-1 mutant was found to be moderately defective in food-induced slowing. In addition, the mutant changed direction more frequently than the wildtype when searching for food, suggesting that SER-1 may play a role in navigational control during foraging. Both these effects required the presence of MOD-1, a 5HT gated chloride channel, and the results indicate that SER-1 and MOD-1 modulate these behaviors through a common pathway. On the basis of expression analysis of a ser-1::GFP translational fusion, SER-1 is prominently located in central, integrating neurons of the head ganglia (RIA and RIC) but not the body wall musculature. The evidence suggests that SER-1 controls locomotion through indirect modulation of neuromuscular circuits and has effects both on speed and direction of movement.
Dernovici
Serge
S
Institute of Parasitology, McGill University, Macdonald Campus, Ste. Anne de Bellevue, Quebec, Canada H9X 3V9.
Starc
Tanja
T
Dent
Joseph A
JA
Ribeiro
Paula
P
D000818:Animals; D030801:Animals, Genetically Modified; D001522:Behavior, Animal / Q000187:drug effects / Q000502:physiology*; D017173:Caenorhabditis elegans; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000502:physiology*; D018118:Chloride Channels / Q000235:genetics / Q000502:physiology; D004268:DNA-Binding Proteins; D004305:Dose-Response Relationship, Drug; D005247:Feeding Behavior / Q000187:drug effects / Q000502:physiology; D005473:Fluoxetine / Q000494:pharmacology; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008124:Locomotion / Q000187:drug effects / Q000502:physiology*; D008954:Models, Biological; D009154:Mutation / Q000502:physiology; D010058:Oviposition / Q000187:drug effects / Q000502:physiology; D044348:Receptors, Serotonin, 5-HT2 / Q000235:genetics / Q000502:physiology*; D012694:Serine / Q000235:genetics; D012701:Serotonin / Q000494:pharmacology; D012702:Serotonin Antagonists / Q000494:pharmacology; D017367:Selective Serotonin Reuptake Inhibitors / Q000494:pharmacology; D013997:Time Factors; D014157:Transcription Factors
D029742:Caenorhabditis elegans Proteins; D018118:Chloride Channels; D004268:DNA-Binding Proteins; D005473:Fluoxetine; D049452:Green Fluorescent Proteins; D044348:Receptors, Serotonin, 5-HT2; D012694:Serine; D012701:Serotonin; D012702:Serotonin Antagonists; D017367:Selective Serotonin Reuptake Inhibitors; D014157:Transcription Factors; C118081:EGL-27 protein, C elegans; C417030:MOD-1 protein, C elegans; C515315:SER-1 protein, C elegans