A theoretical description of microdialysis with mass transport coupled to chemical events

A random-walk simulation of microdialysis is used to examine how a reaction that consumes analyte in the medium external to the probe affects the extr action and recovery processes. The simulations suggest that such a reaction can promote the extraction process while simultaneously inhibiting the rec overy process, which appears to be consistent with recent experimental evid ence of asymmetry in the extraction and recovery of the neurotransmitter, d opamine, during brain microdialysis. This suggests that quantitative microd ialysis strategies that rely on the extraction fraction as a measure of the probe recovery value, such as the no-net-flux method, will produce an unde restimate of the analyte concentration in the external medium when that ana lyte is consumed by a reaction in the external medium. Furthermore, if expe rimental conditions arise under which the kinetics of the reaction are chan ged, then changes in the extraction and recovery processes are likely to oc cur as well. The implications of these theoretical findings for the quantit ative interpretation of in vivo microdialysis results obtained for the neur otransmitter dopamine are examined.