Dopamine transporter activity in the substantia nigra and striatum assessed by high-speed chronoamperometric recordings in brain slices

High-speed chronoamperometric measurements were used to measure clearance of locally applied dopamine (DA) in rat brain slices containing the substantia nigra (SN) or striatum. A comparison of DA signals of similar amplitudes between brain regions revealed that DA clearance was more rapid in the striatum than in the SN, consistent with the known greater distribution of the dopamine transporter (DAT) in the striatum. To clarify the role of the DAT in mediating DA clearance within the SN, slices were superfused with uptake inhibitors with different selectivities for the various monoamine transporters. In the SN, both cocaine and nomifensine significantly increased the amplitude and time course of the DA electrochemical signal. However, neither the serotonin transporter (SERT) inhibitor citalopram nor the norepinephrine transporter (NET) inhibitor desipramine (DMI) produced significant effects on DA clearance. In addition, cocaine and nomifensine affected the clearance parameters of the DA electrochemical signal to a similar extent in both the striatum and the SN, further confirming the functional role of the DAT in both brain regions. Local applications of d- amphetamine resulted in slow, prolonged DA-like electrochemical signals in both the SN and striatum, although the amplitude of the evoked response was larger within the striatum. In contrast, KCl-evoked depolarizations yielded rapid, detectable DA-like signals only within the striatum. Taken together, these data demonstrate the functional role of DAT in mediating DA clearance and release within both the striatum and SN.