D. Zitnan et al., Steroid induction of a peptide hormone gene leads to orchestration of a defined behavioral sequence, NEURON, 23(3), 1999, pp. 523-535
At the end of each molt, insects shed the old cuticle by performing preecdy
sis and ecdysis behaviors. Regulation of these centrally patterned movement
s involves peptide signaling between endocrine Inka cells and the CNS. In I
nka cells, we have identified the cDNA and gene encoding preecdysis-trigger
ing hormone (PETH) and ecdysis-triggering hormone (ETH), which activate the
se behaviors. Prior to behavioral onset, rising ecdysteroid levels induce e
xpression of the ecdysone receptor (EcR) and ETH gene in Inka cells and evo
ke CNS sensitivity to PETH and ETH. Subsequent ecdysteroid decline is requi
red for peptide release, which initiates three motor patterns in specific o
rder: PETH triggers preecdysis I, while ETH activates preecdysis II and ecd
ysis. The Inka cell provides a model for linking steroid regulation of pept
ide hormone expression and release with activation of a defined behavioral
sequence.