title: Detection and monitoring of neurotransmitters--a spectroscopic analysis.
abstract: OBJECTIVE
  We demonstrate that confocal Raman mapping spectroscopy provides rapid, detailed, and accurate neurotransmitter analysis, enabling millisecond time resolution monitoring of biochemical dynamics. As a prototypical demonstration of the power of the method, we present real-time in vitro serotonin, adenosine, and dopamine detection, and dopamine diffusion in an inhomogeneous organic gel, which was used as a substitute for neurologic tissue.
  
  
  METHODS
  Dopamine, adenosine, and serotonin were used to prepare neurotransmitter solutions in distilled water. The solutions were applied to the surfaces of glass slides, where they interdiffused. Raman mapping was achieved by detecting nonoverlapping spectral signatures characteristic of the neurotransmitters with an alpha 300 WITec confocal Raman system, using 532 nm neodymium-doped yttrium aluminum garnet laser excitation. Every local Raman spectrum was recorded in milliseconds and complete Raman mapping in a few seconds.
  
  
  RESULTS
  Without damage, dyeing, or preferential sample preparation, confocal Raman mapping provided positive detection of each neurotransmitter, allowing association of the high-resolution spectra with specific microscale image regions. Such information is particularly important for complex, heterogeneous samples, where changes in composition can influence neurotransmission processes. We also report an estimated dopamine diffusion coefficient two orders of magnitude smaller than that calculated by the flow-injection method.
  
  
  CONCLUSIONS
  Accurate nondestructive characterization for real-time detection of neurotransmitters in inhomogeneous environments without the requirement of sample labeling is a key issue in neuroscience. Our work demonstrates the capabilities of Raman spectroscopy in biological applications, possibly providing a new tool for elucidating the mechanism and kinetics of deep brain stimulation.
authors.affiliation: Department of Physics, University of Texas at El Paso, El Paso, TX, USA. fsmanciu@utep.edu
authors.forename: Felicia S
authors.initials: FS
authors.lastname: Manciu
authors.forename: Kendall H
authors.initials: KH
authors.lastname: Lee
authors.forename: William G
authors.initials: WG
authors.lastname: Durrer
authors.forename: Kevin E
authors.initials: KE
authors.lastname: Bennet
mesh_terms: D000818:Animals; D006801:Humans; D018613:Microscopy, Confocal; D018377:Neurotransmitter Agents / Q000032:analysis*; D013059:Spectrum Analysis, Raman / Q000379:methods*
chemical_list: D018377:Neurotransmitter Agents