Persistent gating deficit and increased sensitivity to NMDA receptor antagonism after puberty in a new mouse model of the human 22q11.2 microdeletion syndrome: a study in male mice

Behavioural characterization of Df(h22q11)/+ mice and wild-type (WT) littermates. (A) Df(h22q11)/+ mice showed decreased prepulse inhibition (PPI). The PPI deficit was reproduced in 6 independent cohorts of mice 6–21 weeks old (n = 12–24/group). We conducted a t test for each week (week 6: t₄₅ = 3.6, p < 0.001; week 9: t₃₀ = 4.8, p < 0.001; week 15: t₂₉ = 6.3, p < 0.001; week 17: t₂₂ = 3.9, p < 0.001; week 19: t₂₂ = 4.9, p < 0.001; week 21: t₂₂ = 6.4, p < 0.001). (B) Haloperidol did not rescue the PPI deficit (n = 12/group, 2-way analysis of variance [ANOVA], genotype: F_1,94 = 69.1, p < 0.001; dose: F_3,94 = 1.02, p = 0.38; genotype × dose: F_3,94 = 0.59, p = 0.63). (C) Clozapine did not rescue the PPI deficit (n = 13/group, 2-way ANOVA, genotype: F_1,87 = 46.3, p < 0.001; dose: F_3,87 = 4.87, p = 0.004; genotype × dose: F_3,87 = 6.14, p < 0.001). (D) Df(h22q11)/+ mice had increased acoustic startle response (ASR). The increased ASR was found in 6 independent cohorts of mice 6–21 weeks old (n = 12–24/group). We conducted a t test for each week (week 6: T_n23,24 = 418, p = 0.004; week 9: T_n16,16 = 204, p = 0.025; week 15: T_n15,16 = 340, p < 0.001; week 17: T_n12,12 = 79, p < 0.001; week 19: t₂₂ = −4.51, p < 0.001; week 21: T_n12,12 = 101, p = 0.005)). (E) Haloperidol did not attenuate the increased ASR (n = 12/group, 2-way ANOVA, genotype: F_1,94 = 88.5, p < 0.001; dose: F_3,94 = 0.060, p = 0.98; genotype × dose: F_3,94 = 0.13, p = 0.95). (F) Clozapine did not attenuate the increased ASR (n = 13/group, 2-way ANOVA, genotype: F_1,87 = 83.1, p < 0.001; dose: F_3,87 = 9.35, p < 0.001; genotype × dose: F_3,87 = 1.49, p = 0.22). (G) Age-dependent hypersensitivity to phencyclidine (PCP)-induced locomotion in Df(h22q11)/+ mice (n = 12/group). We conducted a t test for each week (week 7: t₂₂ = 1.10, p = 0.28 at 2.5 mg/kg and t₂₂ = −0.68, p = 0.50 at 5.0 mg/kg; week 9: T_n11,12 = 90, p = 0.011 for vehicle; T_n12,12 = 187, p = 0.035 at 1.25 mg/kg; t₂₂ = −2.33, p = 0.029 at 2.5 mg/kg and t₂₂ = −0.91, p = 0.37 at 5.0 mg/kg). (H) Hypersensitivity to ketamine-induced locomotion in Df(h22q11)/+ mice (n = 13–16/group, 2-way ANOVA, genotype: F_1,54 = 0.23, p = 0.64; dose: F_11,54 = 25.6, p < 0.001; genotype × dose: F_1,54 = 5.95, p = 0.018; post hoc test within ketamine 10 mg/kg: t = 2.05, p = 0.044). Data are presented as mean ± standard errors of the mean (SEM). *Significant differences between WT and Df(h22q11)/+ mice (*p < 0.05, **p < 0.01, ***p < 0.001). ^#Significant difference within genotype relative to vehicle (^#p < 0.05, ^###p < 0.001).

Biochemical measures in Df(h22q11)/+ mice and wild-type (WT) littermates. (A) Whole tissue content in the prefrontal cortex (PFC). The level of 3,4-dihydroxyphenylacetic acid (DOPAC) was increased in Df(h22q11)/+ mice (n = 8–10/group). We conducted a t test for each analyte (dopamine [DA]: t₁₆ = −0.22, p = 0.83; DOPAC: t₁₆ = −3.85, p = 0.001; homovanillic acid [HVA]: t₁₆ = −0.48, p = 0.64; noradrenaline [NA]: T_n8,10 = 81, p = 0.69; 5-hydroxytryptamine [5-HT]: T_n8,10 = 83, p = 0.56; 5-hydroxyindoleacetic acid [5-HIAA]: t₁₆ = −0.93, p = 0.38). (B) Dorsal striatum (DStr) whole tissue content. The level of DOPAC was increased in Df(h22q11)/+ mice (n = 9–15/group). We conducted a t test for each analyte (DA: t₂₇ = 0.45, p = 0.66; DOPAC: T_n14,15 = 156, p = 0.020; HVA: T_n14,15 = 215, p = 0.84; NA: T_n15,15 = 238, p = 0.85; 5-HT: t₂₈ = 0.91, p = 0.37; 5-HIAA: T_n15,15 = 198, p = 0.16). (C) No genotype effect was detected in the microdialysis of the DStr at baseline (n = 14–15/group). We conducted a t test for each analyte (DA: T_13,15 = 203, p = 0.52; DOPAC: t₂₇ = −0.69, p = 0.50; HVA: t₁₉ = 0.98, p = 0.34; glutamate [Glu]: T_14,14 = 191, p = 0.58). (D) Veratridine (VTD) increased DStr DA similarly in WT and Df(h22q11)/+ mice (n = 14/group, 2-way repeated-meadures ANOVA, genotype: F_1,26 = 0.24, p = 0.63; time: F_8,208 = 18.8, p < 0.001; genotype × time: F_8,208 = 1.35, p = 0.22). (E) Nomifensine increased DStr DA similarly in WT and Df(h22q11)/+ mice (n = 14/group, 2-way repeated-measures ANOVA, genotype: F_1,26 = 0.12, p = 0.74; time: F_10,260 = 25.5, p < 0.001; genotype × time: F_10,260 = 0.79, p = 0.64). (F) PCP increased DStr DA similarly in WT and Df(h22q11)/+ mice (n = 14/group) following both the first (genotype: F_1,28 = 0.003, p = 0.958; genotype × time: F_4,112 = 0.742, p = 0.565) and second PCP challenge (genotype: F_1,28 = 1.632, p = 0.212; genotype × time: F_5,140 = 0.432, p = 0.826). (G) The initial Western blotting showed decreased PFC NeuN (t₂₀ = 2.92, p = 0.009) and increased DStr GluR1 expression (t₂₀ = 2.99, p = 0.007) in Df(h22q11)/+ mice (n = 11/group). However, the NeuN decrease failed to replicate when samples were pooled. Data are presented as means + standard errors of the mean (SEM). *Significant differences between WT and Df(h22q11)/+ mice (*p < 0.05, **p < 0.01). POR = pooled replication; UPO = unpooled.