Serotonergic Chemosensory Neurons Modify the C. elegans Immune Response by Regulating G-Protein Signaling in Epithelial Cells
Adult wild type animals were exposed to M. nematophilum on plates containing exogenous serotonin and the Dar phenotype was scored in their progeny. Treatment with 3.8 mg/ml 5-HT caused a 35% decrease in the number of Dar animals following M. nematophilum infection using standard assay conditions (small lawn) (A). A similar decrease was observed when assay conditions were modified so that animals were unable to avoid the pathogen (big lawn) (A). The Dar phenotype was still decreased when wild type animals were infected in the presence of exogenous serotonin during development, at L1 or L2/3 stage, or 10–18 hours prior to adulthood, at L3/4 stage (B). Similar amounts of M. nematophilum bacteria, labelled using the nucleic acid stain SYTO13, still attached to the anal opening following serotonin treatment (C, D and E) (the rectal opening is indicated with an arrow head in C and D). SYTO13 labeled M. nematophilum was cleared from the anal opening of wild type animals and less than 50% of animals were colonized 90 minutes after transfer to plates without food (F). Treatment of infected animals with 3.8 mg/ml 5-HT significantly decreased the clearance of labeled pathogen from the anal opening (F).