Theory for the impact of basal turnover on dopamine clearance kinetics in the rat striatum after medial forebrain bundle stimulation and pressure ejection.

Although microdialysis measurements suggest that extracellular dopamine concentrations in the rat striatum are in the low nanomolar range, some recent voltammetry studies suggest that the concentration may be considerably higher, perhaps in the micromolar range. The presence of such high dopamine levels in the extracellular space has to be rationalized with the rapid, linear clearance of extracellular dopamine observed after electrical stimulation of the medial forebrain bundle. Kinetic analysis of dopamine clearance after evoked release suggests that the basal extracellular dopamine concentration is below the K(M) of dopamine uptake, which is near 0.