Steroid regulation of octopamine expression during metamorphic development of the moth Manduca sexta.
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.
Lehman
H K
HK
Department of Biological Sciences, Hamilton College, Clinton, New York 13323, USA.
Klukas
K A
KA
Gilchrist
L S
LS
Mesce
K A
KA
D000367:Age Factors; D000818:Animals; D004441:Ecdysterone / Q000378:metabolism* / Q000494:pharmacology; D017952:Ganglia, Invertebrate / Q000166:cytology / Q000378:metabolism; D007814:Larva; D018402:Manduca / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism; D008675:Metamorphosis, Biological / Q000502:physiology*; D006899:Mixed Function Oxygenases / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000378:metabolism; D009655:Octopamine / Q000096:biosynthesis*; D011679:Pupa
D009655:Octopamine; D004441:Ecdysterone; D006899:Mixed Function Oxygenases; C023205:tyramine beta-hydroxylase