The Bag Cell Neuroendocrine System of Aplysia

Abstract

In the opisthobranch mollusc Aplysia one aspect of reproduction, egg-laying, is controlled by a neuropeptide hormone named egg-laying hormone (ELH). The primary structure of ELH from A. californica has been determined; it has 36 amino acid residues and the C-terminal lysine is amidated (Chiu et al. 1979). ELH is synthesized by the bag cell neurons, which are located in two clusters of about 400 neurons each at the anterior pole of the abdominal ganglion. There are at least three genes coding for ELH or ELH- like peptides in Aplysia (Scheller et al. 1983 b). Two of these genes are expressed in the atrial gland, an exocrine gland (Beard et al. 1982) at the end of the reproductive tract (large hermaphroditic duct) which leads to the external genital aperture. The function of these ELH-like peptides, called califms, in the atrial gland are not known, but it has been speculated that they may be pheromones to induce egg-laying in nearby Aplysia (Rothman et al. 1986). The third gene is expressed in the bag cells and codes for ELH. This chapter deals primarily with the bag cell system in Aplysia but some comparative information is included. In the freshwater snail Lymnaea stagnalis the caudodorsal neurons synthesize an ELH and are located in the cerebral ganglion (Joosse and Geraerts 1983).KeywordsAcidic PeptideFreshwater SnailAbdominal GanglionPeptidergic NeuronCell PeptideThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.