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

J Comp Neurol. 2000 Aug 21;424(2):283-96. doi: 10.1002/1096-9861(20000821)424:2<283::aid-cne7>3.0.co;2-z.

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 (TbetaH), 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 TbetaH levels and OA immunoreactivity are regulated by the rise in 20-HE occurring during pupal-adult development. We determined that the levels of TbetaH 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 TbetaH 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 TbetaH. 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 TbetaH observed at the end of metamorphosis.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Age Factors
  • Animals
  • Ecdysterone / metabolism*
  • Ecdysterone / pharmacology
  • Ganglia, Invertebrate / cytology
  • Ganglia, Invertebrate / metabolism
  • Larva
  • Manduca / cytology
  • Manduca / growth & development*
  • Manduca / metabolism
  • Metamorphosis, Biological / physiology*
  • Mixed Function Oxygenases / metabolism
  • Neurons / cytology
  • Neurons / metabolism
  • Octopamine / biosynthesis*
  • Pupa

Substances

  • Octopamine
  • Ecdysterone
  • Mixed Function Oxygenases
  • tyramine beta-hydroxylase