Fig. 4.

Arc/Arg3.1 KO mice show reduced dose-response behavior and cocaine intake but sustained responding for cocaine at higher cost schedules.

(A) Average nose-pokes (active, large boxes = reinforcers earned) and inactive (small boxes) per 3 h session for WT and KO animals during dose-response testing. KO mice earned significantly fewer reinforcers at the 0.1, 0.32, and 1.0 mg/kg/infusion doses than WT mice (n = 8 WT, 9–10 KO). (B) Lower cocaine taking amongst KO mice translated to lower drug intake compared to WT mice at these same unit doses. (C) Average nose-pokes for WT and Arc/Arg3.1 KO mice per 3 h session under schedules of increasing response requirement (cost) (1.0 mg/kg/infusion; n = 7 WT, 6 KO). Time out responses are excluded. For (A & C), active nose-pokes equal reinforcers earned. *p < .05, **p < .01, *** p < .001; data shown are mean ± S.E.M.