Studies on Release Activities of the Neurosecretory Caudo-Dorsal Cells of Lymnaea stagnalis

Abstract

Egg-laying of gastropod molluscs involves a complex series of overt and covert behavioral events that result in the oviposition of the egg mass [1]. These processes are initiated and coordinated by one type of neurosecretory cell. In the freshwater pulmonate Lymnaea stagnalis the cells form paired groups of together ca. 100 caudo-dorsal cells (CDC), located in both cerebral ganglia. They release to ovulation hormone (CDCH) [2], a 4,700 mol.wt. peptide [3], from the periphery of the intercerebral commissure (COM) [4]. Electrophysiological [5] and ultrastructural [6] studies provide indirect evidence that CDCH is released from neurosecretory granules of CDC axon terminals during CDC discharges (synchronous series of action potentials in all CDC lasting ca. 50 min). The presence of the hormone in the blood and the kinetics of its release are, however, as yet not investigated. This chapter provides direct quantitative evidence that CDCH is contained by neurosecretory granules of the CDC and, furthermore, is released into the blood during CDC discharges. We also have attempted to analyse the nervous pathways involved in its release. Finally, we present data on release of various peptides, besides CDCH, by electrically active CDC.