Effects of multiple stressor exposure prior to the two-lever choice tests on lever preference in rats pretreated with diazepam (A, 1 mg/kg, i.p.; B, 2 mg/kg, i.p.) (Experiments 4A and 4B). Response rates for the lever that delivered valued and devalued outcomes on test days 1 and 2 are shown. On both test days, the outcomes (pellets vs. sucrose) were devaluated in a counterbalanced manner. (A) On days 1 and 2, respectively, there was a significant effect of devaluation and treatment, and a devaluation × treatment interaction. Planned contrasts further revealed selective devaluation effects on day 1 in all treatment groups (P < 0.05, each), while on day 2 selective devaluation effects were found in control and stressed rats that received diazepam (P < 0.05, each), but not in stressed rats that received vehicle (P > 0.05). (B) On day 1, there was a significant effect of devaluation and treatment, but no devaluation × treatment interaction. On day 2, there was a significant effect of devaluation and treatment, and, importantly, a significant devaluation × treatment interaction. Planned contrasts revealed a selective devaluation effect in control rats that received diazepam (P < 0.001), but not in stressed rats that received diazepam or vehicle (P > 0.05, each). Sample sizes: (A) diazepam (1 mg/kg) + no stressor (n = 7), diazepam + multiple stressor (n = 8), vehicle (2 mL/kg) + multiple stressor (n = 8); (B) diazepam (2 mg/kg) + no stressor (n = 8), diazepam + multiple stressor (n = 7), vehicle (2 mL/kg) + multiple stressor (n = 7).
