Quantitative aspects of brain microdialysis

The concentration difference method of microdialysis has been widely used for quantification of neurotransmitter concentrations in the extracellular space of the mammalian brain. This Critical Review examines the underlying theoretical basis of the method and shows that the validity of the method requires equality of the microdialysis extraction and recovery ratios of the substance under investigation. Experimental evidence that the extraction and recovery ratios of the neurotransmitter, dopamine, are not equal during microdialysis experiments in the brain of living animals is presented. This evidence leads to the conclusion that the no-net-flux concentration of dopamine is not a quantitative measure of the concentration of this important neurotransmitter in the extracellular space of brain tissue. Hopefully, this information will stimulate further research efforts into the quantitative aspects of chemical analysis in the brain. (C) 2000 Elsevier Science B.V. All rights reserved.