Figure 1.
GAT1 knockout (KO) mice show locomotor hyperactivity and increased sensitivity to psychotomimetic drugs in the open field test.
A1, Total distance traveled of wild-type (WT) and knockout (KO) mice in 30-min tests. A2, Distance traveled of WT and KO mice in each 5 min within the 30-min tests. A3, Total distance traveled of WT and KO in 30-min tests repeated daily for 4 days. n = 8–9 for each genotype. ** p<0.01, *** p<0.001 vs WT, ANOVA. B and C, To test the stimulant effects of NMDAR antagonist MK801 and phencyclidine (PCP), mice were injected i.p. with drug after 30-min acclimation in the open field, and then immediately tested for another 30 min. Locomotor hyperactivity could be induced by MK801 and PCP. GAT1 KO mice showed increased sensitivity to MK801 and PCP. B1, B2, C1 and C2, Distance traveled of WT and KO mice in each 3 min within 1 h tests. B3 and C3, Distance traveled of WT and KO mice in 30-min tests after drug administration. n = 6–8 for each group. * p<0.05, ** p<0.01 vs saline, ANOVA.
Figure 2.
GAT1 KO mice show exaggerated locomotor responses to novelty but impaired object recognition memory.
A, GAT1 KO mice spent more time in the proximity of the novel objects A and B as compared to WT in 5-min tests. n = 12–13 for each group, ** p<0.01, ## p<0.01 vs WT, ANOVA. B, After 1 day, object A was changed to a novel object C. WT mice spent more time in the proximity of the object C than that of object B, indicating a object recognition memory. This memory was impaired in GAT1 KO mice. n = 12–13 for each group, * p<0.05 vs object C, ANOVA.
Figure 3.
GAT1 KO mice show abnormal social behavior.
A1, Representative pictures of the cages of WT and KO mice. A2, Statistical results showing the number of cotton particles in the cages. n = 9–11 for each genotype, ** p<0.01 vs WT, t-test. B, GAT1 KO mice showed more social investigation time to an unfamiliar juvenile conspecific than that of WT mice. n = 9–10 for each genotype, ** p<0.01 vs WT, t-test.
Figure 4.
GAT1 KO mice show impaired prepulse inhibition and latent inhibition.
A1, Startle amplitude to a 120 dB acoustic stimulus was normal in GAT1 KO mice. A2, GAT1 KO mice exhibited significantly reduced percent prepulse inhibition of the acoustic startle response across prepulse intensities (70, 75, 80 dB). n = 9–10 for each genotype, ** p<0.01 vs WT, ANOVA. B, In cued fearing test, GAT1 KO mice showed reduced percent freezing. Pre-exposure to cue without shock significantly impaired the formation of fear memory in WT mice but not in GAT1 KO mice. n = 9–10 for each group, ## p<0.01 vs WT, ** p<0.01vs NP, ANOVA.
Figure 5.
GAT1 KO mice show impaired working memory in Morris water maze and Y-maze tests.
A1, GAT1 KO and WT mice had similar swimming speeds. A2, The latency to find the platform, plotted as function of trials, was significantly longer for GAT1 KO mice as compared to WT mice. n = 10–11 mice×4 days×4 trials for each genotype, ** p<0.001 vs WT, ANOVA. B1, GAT1 KO mice showed significant more total arm entries than that of WT mice in Y-maze test. B2 and B3, The spontaneous alteration was significantly impaired in GAT1 KO mice, as shown by the reduced spontaneous alteration performance and increased alternate arm return ratio. n = 9–10 for each genotype, ** p<0.01 vs WT, t-test.
Figure 6.
Typical (haloperidol) and atypical (clozapine and risperidone) antipsychotic drugs effectively reverse the locomotor hyperactivity in GAT1 KO mice.
n = 7–9 for each group, * p<0.05, ** p<0.01 vs vehicle, ANOVA.
Figure 7.
GAT1 KO mice show normal striatal dopamine levels.
A, The extracellular levels of dopamine and its metabolites were measured in the striatum of freely moving WT and GAT1 KO mice. B–E, GAT1 mice had similar striatal levels of dopamine (DA) and its metabolites (DOPAC and HVA), as well as 5-HT metabolite (5-HIAA). n = 4–6 for each genotype, t-test.
Figure 8.
GAT1 KO mice show increased tonic GABA currents in PFC.
A, Representative traces showing the tonic GABA currents in pyramidal neurons of PFC. B, Statistical results showing that the tonic GABA current was significantly larger in GAT1 KO mice. n = 5 for each group, ** p<0.01 vs WT, t-test. C, Representative traces showing the sIPSCs in pyramidal neurons of PFC. D–G, Statistical results of the amplitude (D), decay time (E), frequency (F) and current area (G) of sIPSCs. GAT1 KO mice showed decreased amplitude but increased decay time. The frequency and current area were not significantly changed. n = 7 for each group, * p<0.05, ** p<0.01 vs WT, t-test. H, The expression of GABAA receptor α1, α2, α5, β, γ2 and δ subunits remained unchanged in the PFC of GAT1 KO mice. left, representative immunoblots; right, statistic results. n = 4–5 for each group, t-test.
Figure 9.
GABAergic antagonist picrotoxin ameliorates the locomotor hyperactivity and working memory defect of GAT1 KO mice.
A, PTX at 3 mg/kg reduced the locomotor hyperactivity in both WT and KO mice in open field. n = 7–8 for each group, ** p<0.01 vs vehicle, ANOVA. B1, PTX at 1 mg/kg reduced the total arm entries of GAT1 KO mice in Y-maze test. B2 and B3, PTX at 1 mg/kg significantly increased the spontaneous alteration performance and reduced the alternate arm return ratio of GAT1 KO mice. n = 7 for each group, * p<0.05, vs vehicle, ANOVA.
Figure 10.
GAT1 KO mice show early onset of schizophrenia-like behaviors.
A1, Total distance traveled of young (4–5 weeks old) WT and KO mice in 30-min tests. A2, Distance traveled of young WT and KO mice in each 5 min within the 30-min tests. A3, Total distance traveled of young WT and KO mice in 30-min tests repeated daily for 4 days. n = 7–9 for each genotype. ** p<0.01, *** p<0.001 vs WT, ANOVA. B, Young GAT1 KO mice showed increased number of cotton particles in the cages. n = 7–9 for each genotype. ** p<0.01 vs WT, t-test. C1, Young GAT1 KO mice showed significant more total arm entries than that of WT mice in Y-maze test. C2 and C3, The spontaneous alteration was significantly impaired in young GAT1 KO mice, as shown by the reduced spontaneous alteration performance and increased alternate arm return ratio. n = 7–9 for each genotype, ** p<0.01 vs WT, t-test.