Three dimensional mapping of neuropeptides and lipids in crustacean brain by mass spectral imaging.

Imaging mass spectrometry is emerging as a powerful tool that has been applied extensively for the localization of proteins, peptides, pharmaceutical compounds, metabolites, and lipids in biological tissues. In this article, a three-dimensional mass spectral imaging (3D MSI) technique was developed to examine distribution patterns of multiple neuropeptide families and lipids in the brain of the crab Cancer borealis. Different matrix/solvent combinations were compared for preferential extraction and detection of neuropeptides and lipids. Combined with morphological information, the distribution of numerous neuropeptides throughout the 3D structure of brain was determined using matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometry (MALDI-TOF/TOF MS). Different localization patterns were observed for different neuropeptide families, and isoforms displaying unique distribution patterns that were distinct from the common family distribution trends were also detected. In addition, multiple lipids were identified and mapped from brain tissue slices. To confirm their identities, MS/MS fragmentation was performed. Different lipid species displayed distinct localization patterns, suggesting their potential different functional roles in the nervous system.