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 D-2 and D-3 receptors, reduced the evoked dopamine release from both regions to the same extent (ED(50), 0.42 mu M for nucleus accumbens; ED(50), 0.46 mu M for striatum). Quinpirole or 7-[H-3]hydroxy-N,N-di-n-propyl-2-aminotetralin (7-OHDPAT), which are much more potent at the D-3 receptor than at the D-2 receptor, reduced the evoked dopamine release from the nucleus accumbens (EDS(50), 0.12 mu M for quinpirole; 0.02 mu M for 7-OHDPAT) much more than the release from the striatum (ED(50) 1.6 mu M for quinpirole; 0.55 mu M for 7-OHDPAT). These results suggest that the contribution of D-3 receptors in nucleus accumbens to regulate dopamine release from dopamine nerve terminals is much greater than that in striatum.