The central nervous system (CNS) of the freshwater snail Lymnaea stagnalis contains several clusters of neuroendocrine cells, which synthesize neuropeptides that act as neurotransmitters, neurohormones, and/or neuromodulators, controlling a broad range of physiological processes. Using a protein chemical approach, we have previously characterized a peptide [named LYCP-A (Hoek et al., 1992], which is produced by the neuroendocrine light yellow cells (LYC), which are present as two clusters of endogenously bursting neurons in the visceral and right parietal ganglion, respectively. 2. A differential screening technique was used to isolate the cDNA that encodes the prohormone of LYCP-A. The prohormone appeared to contain three or four putative neuropeptides, one of which is LYCP-A. The organization of the identified prohormone resembles that of the histidine-rich basic peptide precursor previously identified in the R3-14 neurons of the marine snail Aplysia californica (Campanelli and Scheller, 1987). 3. In situ hybridization analysis indicates that the gene encoding the LYC prohormone is expressed in a subset of the LYC. The LYC release their peptides into the hemolymph from a neurohemal area, which is located around the CNS. In addition, the peptides are released from axonal branches in the aorta of the heart, suggesting a role in the regulation of cardiovascular functions.
