Figure 1.

Cocaine-induced action inflexibilities appear attributable to CORT release

(A) Timeline.

(B) Cocaine increased circulating CORT. n = 6–7 mice/group.

(C) Mice were trained to respond on 2 nose poke apertures for food. Then, pellets associated with 1 nose poke were delivered independently of nose poking (“non-reinforced” condition). Responding at the other port remained reinforced. Behavioral flexibility was assessed the following day in a brief choice test.

(D) Timeline.

(E) Mice were trained to nose poke, with no differences between groups here or in other experiments.

(F) Excess CORT blocked action flexibility, indicated by non-preferential responding at the choice test. The same data can be represented as difference scores (number of responses at the “reinforced”-“non-reinforced” aperture). Zero indicates no preference. Pie charts represent the number of mice/group that preferentially responded at the “reinforced” aperture. n = 10–11 mice/group.

(G) Timeline.

(H) Cocaine caused the same response biases as CORT exposure, and blocking CORT synthesis prior to cocaine prevented those inflexibilities. n = 12 mice/group.

(I) Timeline.

(J) Effects of cocaine on sensitivity to reinforcer devaluation were also assessed. Control mice favored a valued over devalued pellet, but cocaine-exposed mice did not. n = 7–9 mice/group. ∗p ≤ 0.05 following t-test when comparing 2 groups at a single time point and ANOVA when comparing >2 groups and/or multiple time points. Bars and connected dots represent means (±SEMs if indicated), and gray dots and lines represent individual mice.