A review of flux considerations for in vivo neurochemical measurements
by Paul, David W.; Stenken, Julie Ann
The mass transport or flux of neurochems. in the brain and how this flux affects chem. measurements and their interpretation is reviewed. For all endogenous neurochems. found in the brain, the flux of each of these neurochems. exists between sources that produce them and the sites that consume them all within µm distances. Principles of convective-diffusion are reviewed with a significant emphasis on the tortuous paths and discrete point sources and sinks. The fundamentals of the primary methods of detection, microelectrodes and microdialysis sampling of brain neurochems. are included in the review. Special attention is paid to the change in the natural flux of the neurochems. caused by implantation and consumption at microelectrodes and uptake by microdialysis. The detection of oxygen, nitric oxide, glucose, lactate, and glutamate, and catecholamines by both methods are examd. and where possible the two techniques are compared. Non-invasive imaging methods: magnetic resonance, isotopic fluorine MRI, ESR, and positron emission tomog. are also used for different measurements of the above-mentioned solutes and these are briefly reviewed. Although more sophisticated, the imaging techniques are unable to track neurochem. flux on short time scales, and lack spatial resoln. Where possible, imaging detns. of flux are compared to the more classical techniques of microdialysis and microelectrodes.
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