Measurement of neuropeptides: From presence to release

Characterization of neuropeptides is still actively underway. Various resources, both animal and instrument, were utilized to best answer the questions about the presence of peptides. Aplysia californica cerebral neurons were used to verify predicted peptide processing of the putative prohormone AC2. However, the peptides were found to be absent in the forms given by the predictive software when analyzed with MALDI MS. Later studies used Rattus norvegicus brain tissue or microdialysate to look at dynamic peptide responses. The first compared pre- and post-stimulation profiles of rat brain slices that were exposed to a general stimulant. Though a stimulation affect was not seen, many peptides known to be present of the regions of interest, the suprachiasmatic nucleus and supraoptic nucleus, were observed. The final study involved creation of a peptide database for the hippocampus through high resolution mass spectrometry with which to reference microdialysate peptides. The rats were also exposed to various treatments including acute morphine, though the rats were most strongly distinguished by animal and not treatment via principal component analysis. A few peptides from the created hippocampus database were identified to also be in the microdialysate, while there was an interesting pair of fibrinogen protein fragments in the microdialysate that was not seen in the hippocampal extracts. The cumulative approach used in this work allows neuropeptide signaling to be characterized during behavior, enabling new insights into the functions of neuropeptides