Autoradiographic identification of ecdysteroid‐binding cells in the nervous system of the moth Manduca sexta

Abstract

The steroid hormone 20-hydroxyecdysone regulates many aspects of nervous system development in the moth Manduca sexta, including stage-specific neuronal morphology and stage-specific neuronal death. We have used steroid hormone autoradiography to study the distribution of cells that concentrate ecdysteroids in the ventral nervous system of this insect. The ligand was [3H]-ponasterone A, a bioactive phytoecdysone. Tissue was examined from three stages of development: the end of larval life (first day of wandering), the end of metamorphosis (pharate adult), and 4-day-old adults. In the abdominal ganglia of wandering larvae and pharate adults, a subset of neurons including both motoneurons and interneurons exhibited a nuclear concentration of radiolabeled hormone. The pattern of binding was reproducible but stage-specific, with a greater proportion of neurons showing binding in the larvae than in pharate adults. No labeled neurons were found in abdominal ganglia from mature (4-day-old) adults. In the case of the pharate adult ganglia, the ecdysteroid receptor content of specific, identified motoneurons was determined. These results are discussed in light of the responses of these neurons to physiological changes in levels of circulating ecdysteroids.

Programmed cell death in the Drosophila CNS is ecdysone-regulated and coupled with a specific ecdysone receptor isoform

“…The two most striking characteristics of the doomed neurons revealed in the present study are that they exhibit approximately 10-fold higher EcR levels than do other central neurons, and that this elevated expression is due to a single receptor isoform, EcR-A. This result is consistent with autoradiographic studies of the binding of radiolabeled ecdysteroids in Manduca, which showed that doomed neurons had greater steroid-binding capacity than did other neurons (Fahrbach and Truman, 1989). The potential importance of the finding that doomed neurons exhibit a high abundance of EcR-A is highlighted by the observation that the pupal-adult molt represents the only stage in the life of these cells when EcR-A is the predominant isoform (J. W. T., W. S. T., and D. S. H., unpublished data).…”

“…receptor than those that survive (Fahrbach and Truman, 1989). Could quantitative differences in receptor levels control the hormonally regulated aspects of this developmental decision?…”

Co-localization of ecdysteroid receptors and c-fos-like protein in the brain of Manduca sexta larvae

“…I f) tritocerebrum displayed intense c-fos-like immunoreactivity, in contrast to days 1-3 when they were either not stained or only very weakly stained. The latter neurons probably represent neurosecretory cells and/or motoneurons regarding to their size (Fahrbach and Truman 1989) and location.…”

“…This was first suggested many years ago by the ecdysteroid-induced puffing of dipteran salivary gland chromosomes (Clever and Karlson 1960;Ashburner et al 1974) and has more recently been demonstrated autoradiographically by the developmentally specific expression of nuclear ecdysteroid binding sites in the central nervous system and endocrine glands of the fly Calliphora vicina (Bidmon and Koolman 1989) and the larvae and pupae of a moth, Manduca sexta (Fahrbach and Truman 1989;Bidmon et al 1990aBidmon et al , b, 1991Bidmon and Sliter 1990). In all these studies, binding sites appeared at developmental time points critical for the action of ecdysteroids Offprint requests to: H.-J.…”

Remodeling of an identified motoneuron during metamorphosis: Hormonal influences on the growth of dendrites and axon terminals

“…Studies on cultured leg MNs indicated that 20E enhances the complexity of process branching (Prugh et al, 1992;Matheson and Levine, 1999). In addition, both autoradiographic and immunolocalization studies indicate that MNs express ecdysone receptors (Fahrbach and Truman, 1989;Fahrbach, 1992;Truman et al, 1994). Expression of one isoform (EcR-B1) is associated with regressive aspects of remodeling, while expression of another (EcR-A) is associated with growth (Truman et al, 1994).…”