Fig. 1:

Rats (N=6) treated with intra-vmPFC infusions of the selective D1 antagonist SCH-23390 showed attenuated responses to the increases in food motivation elicited by co-infusion of the μ-opioid agonist DAMGO in the progressive ratio task. Intra-vmPFC DAMGO increased responding on the active lever (a), resulting in increased breakpoint (i.e. the last completed ratio, d). Nose-poking was also increased (c). Co-administration of SCH-23390 attenuated increases in active lever pressing (a), breakpoint (d), and nose-poking (c) evoked by treatment with DAMGO alone. There were no effects of any treatment on responding on the inactive lever (b). *P < 0.05, different from all other treatments; ^#P < 0.05, different from 0.25 μg DAMGO/0 μg SCH and 0.25 μg DAMGO/2 μg SCH ‘cocktails’. Error bars depict one SEM.