Figure 3.

Injection hour extracellular level of dopamine (DA) in the nucleus accumbens core (Nacc). Two dialysis samples were collected every 30 min on WD1 (a) and on WD14 (b) to determine the basal level of DA in the Nacc, then two dialysis samples were collected exactly at the time of the usual hours of injection for each treatment without a new injection. Each column represents the extracellular dopamine levels in ng ml⁻¹ (mean±s.e.m.). *P<0.05, **P<0.01, two-tailed t-test (n=6–14).