Endocrinology, Vol 134, 1046-1054, Copyright © 1994 by Endocrine Society

ARTICLES

Persistence of hormone secretion from neuroendocrine cells of aplysia after termination of electrical afterdischarge

NL Wayne and H Wong
Department of Physiology, University of California School of Medicine, Los Angeles 90024.

The bag cell neurons of the marine mollusk Aplysia have been used extensively for investigating the electrophysiology and molecular biology of neurosecretory cells. However, there has been little attempt to carefully describe the pattern of secretion of the 36-amino acid peptide hormone that controls egg-laying behavior. This egg-laying hormone (ELH) is secreted in response to a highly characteristic pattern of action potential firing called the afterdischarge. The purpose of this study was to document the pattern of ELH secretion in response to the bag cell afterdischarge. To accomplish this goal, we developed the first RIA for measurement of ELH. The study was conducted in vitro in excised neural preparations that included the bilateral bag cell clusters; preparations were maintained in static culture of filtered artificial sea water (ASW) at 21-22 C. Afterdischarges were electrically stimulated, and action potentials were monitored via extracellular electrodes. The entire volume of ASW was collected every 5 min and immediately replaced with fresh ASW. In all 20 preparations, ELH levels were low to undetectable before stimulation of the afterdischarge; ELH rose above baseline within 5-10 min of the start of the afterdischarge, reached peak levels near the end or after the end of the afterdischarge, and then remained elevated long after action potentials had ceased firing. These results indicate a temporal dissociation between action potential firing and secretion. We suggest that the afterdischarge is important for triggering intracellular events that culminate in peptide release. Importantly, once these secretion-inducing events have been initiated, they can continue in the absence of further action potential stimulation.

This article has been cited by other articles:

				N. Miller, A. Katzoff, and A. J. Susswein Nitric oxide induces aspects of egg-laying behavior in Aplysia J. Exp. Biol., August 1, 2008; 211(15): 2388 - 2396. [Abstract] [Full Text] [PDF]

				N. G. Hatcher and J. V. Sweedler Aplysia Bag Cells Function as a Distributed Neurosecretory Network J Neurophysiol, January 1, 2008; 99(1): 333 - 343. [Abstract] [Full Text] [PDF]

				N. L. Wayne, W. Lee, S. Michel, and S. B. de Quintana Post-Afterdischarge Depolarization Does Not Stimulate Prolonged Neurohormone Secretion but Is Required for Activity-Dependent Stimulation of Neurohormone Biosynthesis from Peptidergic Neurons Endocrinology, April 1, 2004; 145(4): 1678 - 1684. [Abstract] [Full Text] [PDF]

				N. L. Wayne, W. Lee, S. Michel, J. Dyer, and W. S. Sossin Activity-Dependent Regulation of Neurohormone Synthesis and Its Impact on Reproductive Behavior in Aplysia Biol Reprod, February 1, 2004; 70(2): 277 - 281. [Abstract] [Full Text] [PDF]

				S. Michel and N. L. Wayne Neurohormone Secretion Persists after Post-Afterdischarge Membrane Depolarization and Cytosolic Calcium Elevation in Peptidergic Neurons in Intact Nervous Tissue J. Neurosci., October 15, 2002; 22(20): 9063 - 9069. [Abstract] [Full Text] [PDF]

				N. L. Wayne Regulation of Seasonal Reproduction in Mollusks J Biol Rhythms, August 1, 2001; 16(4): 391 - 402. [Abstract] [PDF]

				W. Lee and N. L. Wayne The Roles of Transcription and Translation in Mediating the Effect of Electrical Afterdischarge on Neurohormone Synthesis in Aplysia Bag Cell Neurons Endocrinology, December 1, 1998; 139(12): 5109 - 5115. [Abstract] [Full Text] [PDF]