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Steroid regulation of octopamine expression during metamorphic development of the moth Manduca sexta
Author(s) -
Lehman Herman K.,
Klukas Kathleen A.,
Gilchrist Laura S.,
Mesce Karen A.
Publication year - 2000
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/1096-9861(20000821)424:2<283::aid-cne7>3.0.co;2-z
Subject(s) - manduca sexta , biology , octopamine (neurotransmitter) , metamorphosis , endocrinology , medicine , sphingidae , biogenic amine , ecdysteroid , manduca , hormone , neurotransmitter , central nervous system , receptor , insect , serotonin , larva , biochemistry , ecology , botany
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. J. Comp. Neurol. 424:283–296, 2000. © 2000 Wiley‐Liss, Inc.