Mean number of sessions to criteria in food-trained M5+/+, M5+/–, and M5–/– mice (males and females combined)
| Genotype | |||
|---|---|---|---|
| Sessions to criteria | +/+ | +/- | -/- |
| Food FR 1 acquisition | 3.17 ± 0.56 (23) | 2.66 ± 0.11 (29) | 2.80 ± 0.28 (20) |
| Food FR 1 extinction | 1.35 ± 0.13 (23) | 1.31 ± 0.12 (29) | 1.75 ± 0.28 (20) |
| Food PR baseline | 5.38 ± 0.69 (13) | 5.25 ± 0.86 (16) | 5.10 ± 0.71 (10) |
| Food PR extinction | 2.92 ± 0.37 (13) | 2.88 ± 0.92 (16) | 1.20 ± 0.13 (10) |
| Cocaine FR 1 baseline | 3.39 ± 0.88 (18) | 2.71 ± 0.28 (24) | 2.80 ± 0.39 (15) |
| Cocaine FR 1 extinction | 5.22 ± 1.15 (18) | 5.21 ± 1.28 (24) | 3.27 ± 0.56 (15) |
Data are group means ± SEM, with n in parentheses. All mice were trained with liquid food under an FR 1 schedule of reinforcement, and a randomly chosen subset was subsequently tested under a PR schedule. After recovery from the catheter implantation surgery, 1.0 mg/kg per infusion of cocaine was made available as the reinforcer. Some attrition occurred during or shortly after surgery. There was no significant effect of genotype or of sex in any of the measures.