Differential effects of dopamine agonists on evoked dopamine release from slices of striatum and nucleus accumbens in rats.

The effects of dopamine receptor agonists on electrically evoked dopamine release from slices of nucleus accumbens were compared with the effects on release from striatal slices in rats. Apomorphine, which has equal potency at the dopamine D2 and D3 receptors, reduced the evoked dopamine release from both regions to the same extent (ED50, 0.42 microM for nucleus accumbens; ED50, 0.46 microM for striatum). Quinpirole or 7-[3H]hydroxy-N,N-di-n-propyl-2-aminotetralin (7-OHDPAT), which are much more potent at the D3 receptor than at the D2 receptor, reduced the evoked dopamine release from the nucleus accumbens (ED50, 0.12 microM for quinpirole; 0.02 microM for 7-OHDPAT) much more than the release from the striatum (ED50, 1.6 microM for quinpirole; 0.55 microM for 7-OHDPAT). These results suggest that the contribution of D3 receptors in nucleus accumbens to regulate dopamine release from dopamine nerve terminals is much greater than in striatum.