Selective detection of neurotransmitters by fluorescence and chemiluminescence
imaging*
Ziqiang Wang and Edward S. Yeung
Ames Laboratory-USDOE and Department of Chemistry,
Iowa State University, Ames, IA 50011, USA
Abstract: In recent years, luminescence imaging has been widely
employed in neurochemical analysis. It has a number of advantages for
the study of neuronal and other biological cells: (1) a particular molecular
species or cellular constituent can be selectively visualized in the
presence of a large excess of other species in a heterogeneous environment;
(2) low concentration detection limits can be achieved because of the
inherent sensitivity associated with fluorescence and chemiluminescence;
(3) low excitation intensities can be used so that long-term observation
can be realized while the viability of the specimen is preserved; and
(4) excellent spatial resolution can be obtained with the light microscope
so subcellular compartments can be identified. With good sensitivity,
temporal and spatial resolution, the flux of ions and molecules and
the distribution and dynamics of intracellular species can be measured
in real time with specific luminescence probes, substrates, or with
native fluorescence. A noninvasive detection scheme based on glutamate
dehydrogenase (GDH) enzymatic assay combined with microscopy was developed
to measure the glutamate release in cultured cells from the central
nervous system (CNS). The enzyme reaction is very specific and sensitive.
The detection limit with CCD imaging is down to mM levels of glutamate
with reasonable response time. We also found that chemiluminescence
associated with the ATP-dependent reaction between luciferase and luciferin
can be used to image ATP at levels down to 10 nM in the millisecond
time scale. Similar imaging experiments should be feasible in a broad
spectrum of biological systems.
*Lecture presented at the IUPAC International Congress
on Analytical Sciences 2001 (ICAS2001), Tokyo, Japan, 6-10 August 2001.
Other presentations are published in this issue,
pp. 1555-1623.
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