Monitoring of Neurotransmitters from Diverse Classes

MULTIANALYTE MONITORING OF NEUROTRANSMITTERS FROM DIVERSE CLASSES 

Contemporary advances in analytical techniques continue to push the boundaries of sensitivity and temporal resolution to track dynamic changes for an ever expanding number of nem-otransmitters. This chapter has so far highlighted published methods for the detection of one or more neurotransmitters from the same category based on similar structural characteristics and chemical properties. Recently, a few studies have reported analytical approaches aimed at measuring multiple classes of neurotransmitters simultaneously to gain a more comprehensive understanding of the complex chemical communication between neurons in the brain. In most cases, the resolution capabilities of LC-based separation have been combined with the multianalyte capacity of MS detection, to monitor several neurotransmitters in the same nm with limits of detection comparable to prior reports. 

Many of the multianalyte studies developed methods for the simultaneous determination of compoimds from the two major classes of neurotransmitters amino acids and bioamines. In one example, DA, serotonin, the serotonin metabolite 5-hydroxyindole acetic acid, glutamate, and GABA were quantified concurrently from tissue preparations using fluorescence detection following derivatization with a novel synthetic compoimd, l,2-benzo-3,4-dihydrocarbazole-9-ethyl 

Recently, Song et al. utilized a derivatization strategy to measure the broadest range of small molecule neurotransmitters reported to date, which included several amino acids, four monoamines, ACh, adenosine, and their major metabolites [54]. Due to the inherent chemical diversity and polar nature of these compounds, all the analytes, with the exception of ACh, were derivatized with benzyl chloride to achieve efficient separation in 8-minute run times by RPLC. Derivatization also improved the sensitivity of ESI—MS/MS analysis and provided a convenient way to generate isotope-labeled internal standards for quantification with commercially available C benzoyl chloride. The LC—MS method described in this study was suitable for the simultaneous detection of all analytes of interest in low-volume dialysis samples with sufficient sensitivity and high-throughput capability to permit fast sampling rates. 

The multianalyte methods described here, whether they employ one comprehensive or parallel detection systems, have enhanced the breath of neurotransmitters amenable to simultaneous monitoring from biological systems. Current studies that employ these methods have enhanced the scope of our imderstanding regarding neurotransmitter communication and the complexity of these interactions in normal and pathological responses. Future analytical developments in the area of multiplexing will imdoubtedly expand the number of transmitter classes measured and the temporal resolution attainable. 

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