In Sal-state, locomotor activity during the preference test was at higher level in GluA1−/− mice than GluA1+/+ mice (Fig. 3B; genotype effect, F1,158 = 49.00, p<0.001), indicative of the phenotypical hyperactivity of the GluA1−/− mice. However, no difference was detected between those groups that had received saline during all conditioning trials (t-test, p>0.05), indicative of complete habituation in the GluA1−/− mice. In GluA1+/+ mice in the Sal-state, locomotor activity decreased in the animals conditioned with 20 mg/kg morphine (conditioning dose effect, F2,158 = 5.07, p<0.01), but no such difference was detected in GluA1−/− mice (genotype×conditioning dose interaction, F2,158 = 4.22, p<0.05). Testing in Mor10-state increased locomotor activity in both mouse lines as compared to testing in Sal-state (testing state effect, F1,158 = 68.11, p<0.001). This increase in locomotor activity also was dependent on genotype and conditioning dose (genotype×conditioning dose×testing state interaction, F2,158 = 3.63, p<0.05): no increase was observed in mice that had received saline in all conditioning trials, but the morphine-conditioned GluA1−/− mice moved more than the corresponding GluA1+/+ mice.
