Abstract

Recent studies demonstrated that vesicular dopamine (DA) uptake can be rapidly altered in synaptic vesicles purified from the striata of stimulant-treated rats. Specifically, a single administration of the plasmalemmal DA transporter inhibitor, cocaine, or the DA D₂ agonist, quinpirole, increases vesicular DA uptake in vesicles purified from the striata of treated rats. These effects of cocaine are prevented by pretreatment with a D₂, but not D₁, DA receptor antagonist. The purpose of the present study was to characterize the effect of a mechanistically different psychostimulant, methamphetamine (METH), on vesicular DA uptake. Results demonstrated that a single administration of this DA-releasing agent rapidly and reversibly decreased vesicular DA uptake. The METH-related decrease in vesicular DA uptake was attenuated by pretreatment with the D₂ antagonist, eticlopride, but not the D₁ antagonist, SCH23390 (R-[+]-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine). Core body temperature did not contribute to the effects of METH on vesicular DA uptake. Neither quinpirole nor cocaine increased vesicular DA uptake when rats were concurrently treated with METH. These studies provide further evidence that psychostimulants rapidly and differentially modify vesicular DA uptake. In addition, these studies demonstrate a complex role for D₂ DA receptors in altering vesicular DA transport.