Current neuroimaging techniques have very limited abilities to directly identify and quantify neurotransmitters from brain sections. We have developed a molecular-specific approach for the simultaneous imaging and quantitation of multiple neurotransmitters, precursors, and metabolites, such as tyrosine, tryptamine, tyramine, phenethylamine, dopamine, 3-methoxytyramine, serotonin, GABA, glutamate, acetylcholine, and L-alpha-glycerylphosphorylcholine, in histological tissue sections at high spatial resolutions. The method is employed to directly measure changes in the absolute and relative levels of neurotransmitters in specific brain structures in animal disease models and in response to drug treatments, demonstrating the power of mass spectrometry imaging in neuroscience.
This paper presents msIQuant, a novel instrument- and manufacturer-independent quantitative mass spectrometry imaging software suite that uses the standardized open access data format imzML. Its data processing structure enables rapid image display and the analysis of very large data sets (>50 GB) without any data reduction. In addition, msIQuant provides many tools for image visualization including multiple interpolation methods, low intensity transparency display, and image fusion. It also has a quantitation function that automatically generates calibration standard curves from series of standards that can be used to determine the concentrations of specific analytes. Regions-of-interest in a tissue section can be analyzed based on a number of quantities including the number of pixels, average intensity, standard deviation of intensity, and median and quartile intensities. Moreover, the suite's export functions enable simplified postprocessing of data and report creation. We demonstrate its potential through several applications including the quantitation of small molecules such as drugs and neurotransmitters. The msIQuant suite is a powerful tool for accessing and evaluating very large data sets, quantifying drugs and endogenous compounds in tissue areas of interest, and for processing mass spectra and images.
Abstract. Many neuroactive substances, including endogenous biomolecules, environmental compounds, and pharmaceuticals possess primary amine functional groups. Among these are catecholamine neurotransmitters (e.g., dopamine), many substituted phenethylamines (e.g., amphetamine), as well as amino acids and neuropeptides. In most cases, mass spectrometric (ESI and MALDI) analyses of trace amounts of such compounds are challenging because of their poor ionization properties. We present a method for chemical derivatization of primary amines by reaction with pyrylium salts that facilitates their detection by MALDI-MS and enables the imaging of primary amines in brain tissue sections. A screen of pyrylium salts revealed that the 2,4-diphenyl-pyranylium ion efficiently derivatizes primary amines and can be used as a reactive MALDI-MS matrix that induces both derivatization and desorption. MALDI-MS imaging with such matrix was used to map the localization of dopamine and amphetamine in brain tissue sections and to quantitatively map the distribution of the neurotoxin β-N-methylamino-L-alanine.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.