IMMUNOGOLD LOCALIZATION OF THE DOPAMINE TRANSPORTER - AN ULTRASTRUCTURAL-STUDY OF THE RAT VENTRAL TEGMENTAL AREA

The dopamine transporter (DAT) plays an important role in the plasmale mmal reuptake of dopamine and, thus, in the termination of normal dopa minergic neurotransmission. DAT is also a major binding site for cocai ne and other stimulants, the psychoactive effects of which are associa ted primarily with the inhibition of dopamine reuptake within mesocort icolimbic dopaminergic neurons. We used electron microscopy with an an ti-peptide anti-serum directed against the N-terminal domain of DAT to determine the subcellular localization of this transporter in the rat ventral tegmental area (VTA), the region that contains the cell bodie s and dendrites of these dopaminergic neurons. We show that in the VTA , almost 95% of the DAT immunogold-labeled profiles are neuronal perik arya and dendrites, and the remainder are unmyelinated axons. Within p erikarya and large proximal dendrites, almost all of the DAT immunogol d particles are associated with intracellular membranes, including sac cules of Golgi and cytoplasmic tubulovesicles. In contrast, within med ium- to small-diameter dendrites and unmyelinated axons, most of the D AT gold particles are located on plasma membranes. In dually labeled t issue, peroxidase reaction product for the catecholamine-synthesizing enzyme tyrosine hydroxylase is present in DAT-immunoreactive profiles. These findings suggest that intermediate and distal dendrites are bot h the primary sites of dopamine reuptake and the principal targets of cocaine and related psychostimulants within dopaminergic neurons in th e VTA.