title: Tyramine Functions independently of octopamine in the Caenorhabditis elegans nervous system.
abstract: Octopamine biosynthesis requires tyrosine decarboxylase to convert tyrosine into tyramine and tyramine beta-hydroxylase to convert tyramine into octopamine. We identified and characterized a Caenorhabditis elegans tyrosine decarboxylase gene, tdc-1, and a tyramine beta-hydroxylase gene, tbh-1. The TBH-1 protein is expressed in a subset of TDC-1-expressing cells, indicating that C. elegans has tyraminergic cells that are distinct from its octopaminergic cells. tdc-1 mutants have behavioral defects not shared by tbh-1 mutants. We show that tyramine plays a specific role in the inhibition of egg laying, the modulation of reversal behavior, and the suppression of head oscillations in response to anterior touch. We propose a model for the neural circuit that coordinates locomotion and head oscillations in response to anterior touch. Our findings establish tyramine as a neurotransmitter in C. elegans, and we suggest that tyramine is a genuine neurotransmitter in other invertebrates and possibly in vertebrates as well.
authors.affiliation: Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Alkema
authors.forename: Melissa
authors.initials: M
authors.lastname: Hunter-Ensor
authors.forename: Niels
authors.initials: N
authors.lastname: Ringstad
authors.forename: H Robert
authors.initials: HR
authors.lastname: Horvitz
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D017173:Caenorhabditis elegans; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D007150:Immunohistochemistry; D008959:Models, Neurological; D008969:Molecular Sequence Data; D009424:Nervous System Physiological Phenomena; D018377:Neurotransmitter Agents / Q000235:genetics / Q000378:metabolism*; D009655:Octopamine / Q000235:genetics / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D014439:Tyramine / Q000378:metabolism*; D014446:Tyrosine 3-Monooxygenase / Q000235:genetics / Q000378:metabolism; D014445:Tyrosine Decarboxylase / Q000235:genetics / Q000378:metabolism
chemical_list: D029742:Caenorhabditis elegans Proteins; D018377:Neurotransmitter Agents; D009655:Octopamine; D014446:Tyrosine 3-Monooxygenase; D014445:Tyrosine Decarboxylase; D014439:Tyramine