Mass Spectral Charting of Neuropeptidomic Expression in the Stomatogastric Ganglion at Multiple Developmental Stages of the Lobster Homarus americanus

The stomatogastric nervous system (STNS) of the American lobster Homarus americanus serves as a useful model for studies of neuromodulatory substances such as peptides and their roles in the generation of rhythmic behaviors. As a central component of the STNS, the stomatogastric ganglion (STG) is rich in neuropeptides and contains well-defined networks of neurons, serving as an excellent model system to study the effect of neuropeptides on the maturation of neural circuits. Here, we utilize multiple mass spectrometry (MS)-based techniques to study the neuropeptide content and abundance in the STG tissue as related to the developmental stage of the animal. Capillary electrophoresis (CE)-MS was employed to unambiguously identify low abundance neuropeptide complements, which were not fully addressed using previous methods. In total, 35 neuropeptides from 7 different families were detected in the tissue samples. Notably, 10 neuropeptides have been reported for the first time in this study. In addition, we utilized a relative quantitation method to compare neuropeptidomic expression at different developmental stages and observed sequential appearance of several neuropeptides. Multiple isoforms within the same peptide family tend to show similar trends of changes in relative abundance during development. We also determined that the relative abundances of tachykinin peptides increase as the lobster grows, suggesting that the maturation of circuit output may be influenced by the change of neuromodulatory input into the STG. Collectively, this study expands our knowledge about neuropeptides in the crustacean STNS and provides useful information about neuropeptide expression in the maturation process.