Effect of general microdialysis-induced depletion on extracellular dopamine.

Continuous sampling by microdialysis induces a general depletion of all low molecular weight materials around the microdialysis probe. The effect of this depletion on the estimation of extracellular dopamine (DA) concentration was evaluated for various degrees of depletion. The basal level of DA in the striatum of male Wistar rats was estimated by the zero net flux method at six different flow rates ranging form 0.3 to 1.6 microL/min. The extracellular DA concentrations in the striatum of male rats measured by this method were found not to differ significantly from one flow rate to another (p > 0.05) with a mean of 6.5 nM +/- 0.11. These finding suggest that the estimation of extracellular dopamine by quantitative microdialysis is independent of the flow rate and that the depletion of other extracellular substances around the probe has no effect on the determination of the extracellular concentration of dopamine.