Steroid regulation of octopamine expression during metamorphic development of the moth Manduca sexta

Herman K. Lehman, Kathleen A. Klukas, Laura S. Gilchrist, Karen A. Mesce

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26 Scopus citations

Abstract

Octopamine (OA), a biogenic amine similar to norepinephrine, has profound and well-documented actions on the nervous systems of invertebrates. In the insect, Manduca sexta, we examined the developmental plasticity of OA synthesis, studied its endocrine regulation, and observed previously undescribed OA-immunoreactive (ir) neurons. We found that levels of tyramine beta-hydroxylase (TβH), an essential enzyme for the biosynthesis of OA, increase during metamorphosis. Based on the established and influential roles of the steroid hormone 20-hydroxyecdysone (20-HE) during development, we tested the hypothesis that increases in TβH levels and OA immunoreactivity are regulated by the rise in 20-HE occurring during pupal-adult development. We determined that the levels of TβH in the terminal abdominal ganglion (neuromeres 6-9) remain at a constant level during pupal development and the early stages of adult development. Beginning at ca. pupal stage 8, however, the levels of TβH begin to rise, reaching a maximum level by pupal stage 12. By removing the source of ecdysteroid hormone through ligation, and by subsequent replacement of 20-HE via infusion, we found evidence indicating that the preadult rise of 20-HE is both necessary and sufficient for the increased levels of TβH. During the course of our study, we also identified previously unreported OA-ir neurons. In particular, adult-specific OA-ir lateral cells were found, as were relatively small OA-ir dorsal median pairs that doubled in size during adult development. Abdominal ganglia not exposed to the preadult rise in 20-HE possessed neither the OA-ir lateral neurons nor the somatic growth of the smaller OA-ir median neurons. These newly described OA-ir neurons probably contribute to the steroid-induced elevations of TβH observed at the end of metamorphosis. (C) 2000 Wiley-Liss, Inc.

Original languageEnglish (US)
Pages (from-to)283-296
Number of pages14
JournalJournal of Comparative Neurology
Volume424
Issue number2
DOIs
StatePublished - Aug 21 2000

Keywords

  • 20-hydroxyecdysone
  • Biogenic amines
  • Median neuroblast
  • Neurotransmitter synthesis
  • Tobacco hornworm
  • Tyramine β-hydroxylase

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