Neurosecretion of egg-laying hormone and other peptides from electrically active bag cell neurons of Aplysia

Abstract

Radiolabeled peptides released from an isolated cluster of bag cell neurons, during an afterdischarge, were compared with the polypeptide egg-laying hormone (ELH), 4500 daltons, pI [isoelectric point] 9.0-9.3, as purified from homogenates of bag cell clusters. A peptide, labeled with methionine, leucine and arginine, which is selectively released from afterdischarging bag cell clusters comigrates with marker ELH, purified from cluster homogenates, on P-6 gel filtration columns and subsequent isoelectric focusing gels. At least 3 other presumed peptides of unknown function are also released, including 1 of 5000-6000 MW, pI 4.5-5.0. When bag cells after discharge in vitro, bioactive material is released that will induce egg laying when injected into an Aplysia. This released bioactive material also comigrates with bioactive material from cluster homogenates on P-6 columns. ELH (4500 MW, pI 9.0-9.3), as purified from bag cell cluster homogenates, is also the major form secreted from bag cells that induces egg laying. This purified ELH can now be used to study the physiological effects of a secreted neurohoromone and their relationship to behavior.