TY - JOUR T1 - Neurohormone Secretion Persists after Post-Afterdischarge Membrane Depolarization and Cytosolic Calcium Elevation in Peptidergic Neurons in Intact Nervous Tissue JF - The Journal of Neuroscience JO - J. Neurosci. SP - 9063 LP - 9069 DO - 10.1523/JNEUROSCI.22-20-09063.2002 VL - 22 IS - 20 AU - Stephan Michel AU - Nancy L. Wayne Y1 - 2002/10/15 UR - http://www.jneurosci.org/content/22/20/9063.abstract N2 - The purpose of this work was to test the hypothesis that an electrical afterdischarge (AD) causes prolonged elevation in cytosolic calcium levels that is associated with prolonged secretion of egg-laying hormone (ELH) from peptidergic neurons in intact nervous tissue of Aplysia. Using a combination of radioimmunoassay measurement of ELH secretion, electrophysiological measurement of membrane potential, and optical imaging of the concentration of intracellular free calcium ions ([Ca2+]i), we verified that there was persistent secretion of ELH after the end of the AD; this was accompanied by prolonged post-AD membrane depolarization and prolonged post-AD elevation in [Ca2+]i. Extracellular treatment with the calcium chelator EGTA had no effect on the pattern or magnitude of ELH secretion or on the post-AD membrane potential (Vm) and post-AD Ca2+ signal, ruling out a role for extracellular calcium in the post-AD elevation of [Ca2+]i. BothVm and [Ca2+]i returned to baseline well before ELH secretion, such that neither prolonged membrane depolarization nor prolonged Ca2+ signaling can fully account for the extent of the persistent secretion of ELH. These findings suggest a unique relationship between membrane excitability, Ca2+ signaling, and prolonged neuropeptide secretion. ER -