Characterization of dopamine transport in crude synaptosomes prepared from rat medial prefrontal cortex

Accumulating evidence suggests that dopamine (DA) uptake into mesocortical neurons may be regulated through mechanisms that are markedly different from those observed in nigrostriatal or mesoaccumbens systems. The current studies were conducted to develop a rapid and sensitive DA uptake assay in crude synaptosomes prepared from the medial prefrontal cortex (mPFC) of a single animal. Uptake of DA into the mPFC was saturable, linear with respect to protein concentration, time dependent, and sensitive to the effects of monoamine transport inhibitors. Saturation analysis revealed the K(m) and V(max) values for DA transport in the mPFC were approximately 60 nM and 6.5 pmol/min mg protein, respectively. A significant amount of DA uptake in the mPFC was more sensitive to inhibition by nisoxetine compared to GBR12909, fluoxetine (FLX), and cocaine (COC), suggesting the norepinephrine transporter (NET) plays an important role in the clearance of DA within this region. The described assay conditions would be useful in examining DA uptake within specific brain regions obtained from a single animal.