Application of reverse microdialysis in the evaluation of neural regulation of cardiovascular functions

Microdialysis is a relatively new bioanalytical sampling technique with remarkable potential. In it most popular application, an endogenous substance whose concentration changes in response to physiologic perturbation or pharmacologic agent is removed from the extracellular space into the probe. The collected samples may then be quantified by various analytical methods. A more recent application of microdialysis is the introduction of a substance into the extracellular space via the probe. Since the direction of flow of the substance of interest is opposite to that in the conventional form of microdialysis, this application is often known as reverse microdialysis. This mini-review focuses on the advantages of applying reverse microdialysis to biomedical research. As illustrated by results from our laboratory obtained under the general research theme of central neural regulation of cardiovascular functions, this method offers the benefit of manipulating and estimating the concentration of the substance in the extracellular space. It also allows for simultaneous recovery of endogenous substances whose levels are altered because of the exogenously applied substance. The functional significance of these chemical changes can then be correlated to concurrent alterations in an appropriate physiologic parameter. We also discussed the importance of the dimension of the dialysis probes and ways to estimate the extracellular concentration of chemical substances during reverse microdialysis. Copyright (C) 1999 Elsevier Science B.V.