(A) Schematic of amphetamine sensitization protocol. (B) Locomotor activity in the open field after vehicle (Veh) or Amphetamine (Amph) injection. There were no between group differences in activity on the habituation days (Days 1 and 2). Over the subsequent 5 treatment days, CTRL mice showed sensitization to Amph while DAT GLS1 cHET mice did not (RM ANOVA, significant genotype X treatment X day interaction, F(4,296) = 4.4, p=0.002, ES partial η2 = 0.06; RM ANOVA within Amph-treated mice, significant genotype X day interaction, F(4,160) = 5.9, p<0.001, ES partial η2 = 0.112). *p<0.016 indicates significantly different from CTRL Amph-treated mice, after Bonferroni correction for 3 comparisons (α = 0.016). On the Veh challenge day (day 18), Amph-treated mice showed a modest increase in locomotion relative to Veh-treated mice independent of genotype. # indicates significant treatment effect (F(1,74)= 4.03, p=0.048; partial η2 = 0.052), but no main effect of genotype (F(1,74)< 0.001, p=1) or significant interaction (F(1,74)= 0.163, p=0.688). On the challenge day (Day 19), Amph-treated mice showed increased locomotion relative to Veh-treated mice independent of genotype. # indicates significant treatment effect (two-way ANOVA: F(1,74) = 13.7, p<0.001, ES partial η2 = 0.112), with no significant genotype effect (F(1,74) = 2.76, p=0.101), but a trend for interaction (F(1,74) = 3.18, p=0.078). (C) On the Amph challenge day Veh-treated (left) and Amph-treated mice (right) received Amph and activity was monitored for 90 min. Veh-treated mice showed no genotypic difference in their response to Amph (RM ANOVA genotype effect, F(1,74) = 0.012, p=0.91; genotype X time interaction, F(1,74) = 0.53, p=0.83). Amph-treated CTRL mice showed a sensitized response to Amph while DAT GLS1 cHET did not. ♢ # indicate a significant genotype difference (RM ANOVA, F(1,40) = 89.3, p=0.034, ES partial η2 = 0.107), and significant effect of time (F(8,320) = 12.8, p<0.0001, ES partial η2 = 0.243), but no significant interaction (F(8,320) = 0.576, p=0.798). stopGLS1 mice, with a global GLS1 HET reduction, show attenuated amphetamine sensitization; see Figure 6—figure supplement 1. ΔGLS1 HET mice, generated by breeding floxGLS1 mice with mice expressing cre under the control of the ubiquitous tamoxifen-inducible ROSA26 promoter (Figure 6—figure supplement 2), also show attenuated amphetamine sensitization (Figure 6—figure supplement 3). (D) Schematic of latent inhibition protocol. (E) On the tone test day (Day 3), the percent time freezing for the 3 min before and 8 min after CS (tone) presentation are shown for CTRL (left) and DAT GLS1 cHET mice (right). CTRL non-preexposure (NPE) and preexposure (PE) groups did not differ, evidencing no LI (RM ANOVA during CS, no preexposure effect, F(2,12) = 0.127, p=0.728; nor preexposure X time interaction, F(7,84) = 1.66, p=0.129). DAT GLS1 cHET NPE and PE groups did not differ before CS presentation (PE effect, F(1,20) = 0.646, p=0.431; interaction, F(2,40) = 2.12, p=0.132); during CS presentation, PE mice showed less freezing than NPE mice, evidencing potentiated LI (RM ANOVA, significant time X PE treatment interaction, F(7,140)= 2.88, p=0.008, ES partial η2 = 0.126). *p<0.006 indicates significant different between PE and NPE groups, after Bonferroni correction for 8 comparisons (α = 0.006). (F) Percent total time freezing during 8 min CS presentation on the tone test (Day 3). DAT GLS1 cHET PE mice, but not CTRL mice, showed less freezing during CS presentation, evidencing potentiated LI (two-way ANOVA, significant genotype X PE treatment interaction, F(1,32)= 5.3, p=0.028, ES partial η2 = 0.334; no significant genotype effect, F(1,32)= 0.145, p=0.71, nor PE effect, F(1,32)= 1.52, p=0.227). Within the NPE group, there was no genotype effect, showing that learning was not affected in DAT GLS1 cHETs (F(1,15)= 1.56, p=0.23). * indicates significant pre-exposure effect within the DAT GLS1 cHET group by ANOVA (F(1,20) = 10.03, p=0.005, ES partial η2 = 0.334). stopGLS1 mice (Gaisler-Salomon et al., 2009b), as well as ΔGLS1 HET mice (Figure 6—figure supplement 3), both with a global GLS1 reduction, show potentiation of LI. (G) Schematic of the EMX1 GLS1 cHET mouse brain (sagittal view) illustrating the GLS1 cHET genotype in forebrain. See Figure 6—figure supplement 4. (H) Novelty-induced locomotion and habituation to the open field did not differ between CTRL (white circles) and EMX1 GLS1 cHET mice (grey circles). RM ANOVA showed a significant time effect (F(5,170) = 138.1, p<0.0001, ES partial η2 = 0.802); no significant genotype effect (F(1,34) = 0.599, p=0.44); and no significant interaction (F(5,170) = 0.820, p=0.537). (I) Both CTRL and EMX1 GLS1 cHET mice showed sensitization to Amph during the 5 treatment days (RM ANOVA: days X drug treatment effect, F(4,128)= 11.33, p<0.0001, ES partial η2 = 0.259; there was no significant day X drug treatment X genotype interaction, F(4,128)= 0.161, p=0.96). On the Veh challenge day, there were no significant differences between genotypes of drug-treatment groups. On the Amph challenge day, Amph-treated mice showed a sensitized response relative to Veh-injected mice, independent of genotype. # indicates a significant main effect of drug treatment (F(1.32) = 16.83, p<0.0001, ES partial η2 = 0.330). (J) EMX1 GLS1 cHET mice did not show potentiation of LI. Percent time freezing during the 8 min CS presentation on the tone test day (Day 3) did not differ between NPE and PE groups, independent of genotype (two-way ANOVA: no significant main effect of genotype, F(1,35)= 0.281, p=0.60; PE, F(1,35)= 0.163, p=0.69; or interaction, F(1,35)= 0.586, p=0.45). EMX1 GLS1 cHET mice, as well as ΔGLS1 HET and DAT GLS1 cHET mice, showed clozapine-induced potentiation of LI (Figure 6—figure supplement 5). In all graphs, the number of mice is shown above the bars or next to the lines. See Figure 6—source data 1.xlsx for source data and statistical analysis.