D1-D2 dopamine receptor interaction within the nucleus accumbens mediates long-loop negative feedback to the ventral tegmental area (VTA)

The objective of the present study was to examine the effects of perfusion of dopamine (DA) D1- and D2-like receptor agonists in the nucleus accumbens (ACB) on the long-loop negative feedback regulation of mesolimbic somatodendritic DA release in the ventral tegmental area (VTA) of Wistar rats employing ipsilateral dual probe in vivo microdialysis. Perfusion of the ACB for 60 min with the D1-like receptor agonist SKF 38393 (SKF, 1-100 microM) dose-dependently reduced the extracellular levels of DA in the ACB, whereas the extracellular levels of DA in the VTA were not changed. Similarly, application of the D2-like receptor agonist quinpirole (Quin, 1-100 microM) through the microdialysis probe in the ACB reduced the extracellular levels of DA in the ACB in a concentration-dependent manner, whereas extracellular levels of DA in the VTA were not altered. Co-application of SKF (100 microM) and Quin (100 microM) produced concomitant reductions in the extracellular levels of DA in the ACB and VTA. The reduction in extracellular levels of DA in the ACB and VTA produced by co-infusion of SKF and Quin was reversed in the presence of either 100 microM SCH 23390 (D1-like antagonist) or 100 microM sulpiride (D2-like antagonist). Overall, the results suggest that (a) activation of dopamine D1- or D2-like receptors can independently regulate local terminal DA release in the ACB, whereas stimulation of both subtypes is required for activation of the negative feedback pathway to the VTA.