Fig. 2.

Autoreceptor and heteroreceptor inhibition of DA release. a, DA overflow was evoked once per 2 min in slices of WT (▵, n = 3) and D₂−/− (●, n = 5) mice. After stable responses were obtained, slices were superfused for 10 min with the D₂/D₃ receptor agonist quinpirole (0.5 μm). The peak amplitude of evoked DA overflow, normalized to DA overflow evoked by three stimuli before the switch to quinpirole, is plotted versus time (means ± SEM; double asterisks denote a statistically significant difference from WT with p < 0.01). The superfusion with quinpirole is indicated by the gray area. b, Effects of the GABA_B agonist R(+)-baclofen (100 μm) on evoked DA overflow in slices from D₂−/− mice (n = 6) and WT mice (n = 8). As in a, the normalized peak response is plotted versus time. The gray areaindicates the 10 min superfusion with R(+)-baclofen. There was no statistically significant difference between WT and D₂−/− mice (p > 0.05).Dotted lines indicate normalized amplitude = 1.