Uptake and release of dopamine through the rat dopamine transporter expressed in Xenopus laevis oocyte: evaluation by voltammetric measurement of intracellular dopamine concentration.

An attempt was made to evaluate the uptake and release of dopamine (DA) through the rat dopamine transporter (DAT) expressed in Xenopus laevis oocytes. A carbon electrode was placed intracellularly into the oocyte to measure directly the intracellular concentration of DA ([DA]i) by voltammetric analyzer. Oocytes injected with the rat DAT cRNA showed a rapid rise and fall of [DA]i in response to the perfusion solution in the presence and absence of DA. In the control experiment, oocytes injected with water showed no response to external DA. An increase in [DA]i which was induced in control oocytes injected with DA into cytosol was not affected by DA-free perfusion solution, suggesting that in the absence of the transporter the accumulated DA never leaked out from the cell. Thus, the bi-directional DA fluxes through the transporter were demonstrated electrochemically in real time on-line mode.