Fig. 2: Drug-induced locomotor hyperactivity and prepulse inhibition during adolescence and adulthood.

A Amphetamine-induced hyperactivity (% increase from pretreatment baseline (left) and % change from vehicle saline-treated animals (right)). % increase from baseline (left): Significant effect of treatment (F_(1,129) = 172.19, P < 0.001) and an age x treatment interaction (F_{(2, 129)} = 3.49, P = 0.034) with amphetamine inducing locomotor hyperactivity (ANOVA test with age, sex and treatment as independent factors). Examining individual treatments using a two-way ANOVA, saline vehicle-treated animals showed no effect of age (F_{(2, 60)} = 0.14, P = 0.874), sex (F_{(1, 60)} = 0.95, P = 0.334), or age × sex interaction (F_{(2, 60)} = 0.96, P = 0.391). Amphetamine-treated animals showed a significant effect of age (F_{(2, 68)} = 3.78, P = 0.028), but no sex (F(_{1, 68}) = 1.04, P = 0.313) or sex × age interaction (F_{(2, 68)} = 2.16, P = 0.123). Dunnett’s multiple comparisons post hoc tests using adult mice as the reference group showed 12 W mice were not significantly different to 4.5 W (P = 0.514) or 6 W mice (P = 0.177). However, since we observed an effect of age, Bonferroni’s multiple comparisons test revealed mid-adolescent animals showed a significantly lower drug-induced locomotor response compared to early adolescent mice (P = 0.041). % change from vehicle saline-treated animals (right): Significant effect of age (F_(2,68) = 4.18, P = 0.020) but not sex (F_(2,68) = 2.42, P = 0.125) or age × sex interaction effects (F_(2,68) = 2.98, P = 0.058), two-way ANOVA. Dunnett’s multiple comparisons post hoc tests using adult mice as the reference group showed 12 W mice were not significantly different to 4.5 W (P = 0.391) or 6 W mice (P = 0.173). Since we observed an effect of age, Bonferroni’s multiple comparisons test showed mid-adolescent animals were significantly different early adolescent mice (P = 0.024). Data for individual mice are displayed together with mean ± SEM. #Main effect of age P < 0.05; *P < 0.05 between 4.5 and 6 W. Each point represents an individual mouse. B Percentage prepulse inhibition (average for prepulse 6, 12 and 18 combined only for the purpose of data visualization). Significant effect of age (F_(2,85) = 7.76, P < 0.001) but no effect of sex (F_(2,85) = 0.11, P = 0.746) nor age × sex interaction effects (F_(2,85) = 0.13, P = 0.879). Both 4.5 W (P = 0.018) and 6 W (P < 0.001) mice were significantly different to 12 W mice; repeated measures (3 prepulses) ANOVA with post hoc Dunnett’s multiple comparisons test using adult mice as the reference group. See Fig. S3B for additional analysis on effect of age on prepulse inhibition. Data for individual mice are displayed together with mean ± SEM. #Main effect of age P < 0.05, * P < 0.05, **P < 0.01 relative to 12 W sex-matched mice. Each point represents an individual mouse.