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Synaptic neuropeptide release induced by octopamine without Ca2+ entry into the nerve terminal
Edited by Eve Marder, Brandeis University, Waltham, MA, and approved February 4, 2011 (received for review December 1, 2010)

Abstract
Synaptic release of neurotransmitters is evoked by activity-dependent Ca2+ entry into the nerve terminal. However, here it is shown that robust synaptic neuropeptide release from Drosophila motoneurons is evoked in the absence of extracellular Ca2+ by octopamine, the arthropod homolog to norepinephrine. Genetic and pharmacology experiments demonstrate that this surprising peptidergic transmission requires cAMP-dependent protein kinase, with only a minor contribution of exchange protein activated by cAMP (epac). Octopamine-evoked neuropeptide release also requires endoplasmic reticulum Ca2+ mobilization by the ryanodine receptor and the inositol trisphosphate receptor. Hence, rather than relying exclusively on activity-dependent Ca2+ entry into the nerve terminal, a behaviorally important neuromodulator uses synergistic cAMP-dependent protein kinase and endoplasmic reticulum Ca2+ signaling to induce synaptic neuropeptide release.
Footnotes
- 1To whom correspondence should be addressed. E-mail: elevitan{at}pitt.edu.
Author contributions: D.S. and E.S.L. designed research; D.S. and G.M.Z. performed research; T.G. and R.S.H. contributed new reagents/analytic tools; D.S., G.M.Z., and E.S.L. analyzed data; and E.S.L. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
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