Steroid regulation of octopamine expression during metamorphic development of the mothManduca sexta

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.

Characterization of tyramine β-hydroxylase, an enzyme upregulated by stress in Periplaneta americana

“…Incubation of crude nerve cord extract with tyramine results in the formation of OA, which is detectable by ELISA assay. This assay requires catalase (Wallace 1976, Lehman et al 2000a and is based on the conversion of tyramine to OA by the TBH contained in the tissue protein extract. Previous studies conducted on several animals including cockroach used radioactive HPLC detection technique (Lehman et al 2000a,b), which is a very precise assay for activity quantification.…”

“…Biochemical property analysis of a partially purified TBH from the thoracic nervous system of the lobster Homarus americanus had demonstrated that TBH is necessary for the hydroxylation of tyramine to produce OA and that this reaction is dependent on pH, ascorbic acid, copper, and catalase (Wallace 1976, Lehman et al 2000a. During Manduca sexta development, TBH activity is increased in the brain and in the ganglia, in correlation with an increase in OA levels during metamorphosis reflecting that OA levels are developmentally regulated (Lehman et al 2000a,b).…”

Division of labor in the honey bee (Apis mellifera): the role of tyramine β-hydroxylase

“…3 H]tyramine to [ 3 H]OA and has been used previously to characterize T␤h in the developing nervous system of the hawk moth, Manduca sexta (Lehman et al, 2000a;Lehman et al, 2000b). Here, individually dissected bee brains were each homogenized in 10·l bee saline and 2·l samples were assayed for total protein concentration.…”

Development and steroid regulation of RFamide immunoreactivity in antennal-lobe neurons of the sphinx mothManduca sexta

“…This could suggest an inhibition of RFamide expression occurring during normal development between P8 and P12, which is absent after early 20E injection. On the other hand the lack of a plateau phase could simply reflect the fact that a single hormone injection does not mimic the pupal ecdysteroid peak as well as a continuous hormone infusion might do (Lehman et al, 2000). Furthermore, synaptotagmin staining revealed that not only the presence of RF-amides, but also the formation of glomeruli, occurred earlier than during normal development.…”

“…The pupal 20E peak regulates the fusion of thoracic and abdominal ganglia (Amos et al, 1996), it controls cell proliferation during genesis of the optic lobes and the retina but also programmed cell death of optic lobe neuroblasts Truman, 1998a,b, 2000). Specifically, 20E also regulates the pupal expression of tyramine β-hydroxylase, an essential enzyme for octopamine biosynthesis (Lehman et al, 2000). We recently showed that 20E injections early in metamorphosis lead to elevated concentrations of the second messenger molecule cyclic guanosine monophosophate in LC neurons, which during normal development does not occur before stages P7/8 (Schachtner et al, 1998(Schachtner et al, , 1999.…”