Tyramine and octopamine have opposite effects on the locomotion of Drosophila larvae

Authors

  • Sudipta Saraswati,

    1. Department of Biological Sciences, University of Iowa, Iowa City, Iowa 52242
    Current affiliation:
    1. Department of Brain and Cognitive Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139
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    • These authors contributed equally to the manuscript.

  • Lyle E. Fox,

    Corresponding author
    1. Department of Biological Sciences, University of Iowa, Iowa City, Iowa 52242
    • Department of Biological Sciences, University of Iowa, Iowa City, Iowa 52242
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    • These authors contributed equally to the manuscript.

  • David R. Soll,

    1. Department of Biological Sciences, University of Iowa, Iowa City, Iowa 52242
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  • Chun-Fang Wu

    1. Department of Biological Sciences, University of Iowa, Iowa City, Iowa 52242
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Abstract

Biogenic amines are believed to play important roles in producing behaviors. Although some biogenic amines have been extensively studied in both vertebrates and invertebrates, little is known about the effects of trace amines like tyramine and octopamine. We investigated how trace amines affect behaviors using quantitative morphometric methods on DrosophilaTβhnM18 and iavN mutants that have altered levels of tyramine and octopamine. Locomotion of wild-type and mutant third instar larvae was analyzed using Dynamic Image Analysis System (DIAS) software. We found that TβhnM18 mutants, with elevated tyramine levels and reduced octopamine levels, had a severe locomotion phenotype. Mutant larvae spent much more time in pausing episodes than wild-type larvae and displayed a reduction in speed and linear translocation. The locomotion phenotype was partially rescued by feeding TβhnM18 larvae octopamine, an effect that could be nullified with simultaneous feeding of tyramine. Feeding TβhnM18 larvae yohimbine, an agent that inhibits the activity of Drosophila tyramine receptors, also improved some locomotion parameters. Feeding both octopamine and yohimbine further improved rescue efficiency. Simultaneously reducing the octopamine and tyramine levels as in iavN larvae, in contrast, led to a less severe behavioral phenotype than that of TβhnM18 mutants. Feeding iavN larvae either tyramine or octopamine exerted only a minor improvement in locomotion. These results suggest that tyramine and octopamine have opposite effects on Drosophila larval locomotion regulation and that a balance between the two is important in producing normal behavior. © 2003 Wiley Periodicals, Inc. J Neurobiol 58: 425–441, 2004

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