Glutathione Deficiency during Early Postnatal Development Causes Schizophrenia-Like Symptoms and a Reduction in BDNF Levels in the Cortex and Hippocampus of Adult Sprague-Dawley Rats

Abstract

Growing body of evidence points to dysregulation of redox status in the brain as an important factor in the pathogenesis of schizophrenia. The aim of our study was to evaluate the effects of l-buthionine-(S,R)-sulfoximine (BSO), a glutathione (GSH) synthesis inhibitor, and 1-[2-Bis(4-fluorophenyl)methoxy]ethyl]-4-(3-phenylpropyl)piperazine dihydrochloride (GBR 12909), a dopamine reuptake inhibitor, given alone or in combination, to Sprague-Dawley pups during early postnatal development (p5-p16), on the time course of the onset of schizophrenia-like behaviors, and on the expression of brain-derived neurotrophic factor (BDNF) mRNA and its protein in the prefrontal cortex (PFC) and hippocampus (HIP) during adulthood. BSO administered alone decreased the levels of BDNF mRNA and its protein both in the PFC and HIP. Treatment with the combination of BSO + GBR 12909 also decreased BDNF mRNA and its protein in the PFC, but in the HIP, only the level of BDNF protein was decreased. Schizophrenia-like behaviors in rats were assessed at three time points of adolescence (p30, p42-p44, p60-p62) and in early adulthood (p90-p92) using the social interaction test, novel object recognition test, and open field test. Social and cognitive deficits first appeared in the middle adolescence stage and continued to occur into adulthood, both in rats treated with BSO alone or with the BSO + GBR 12909 combination. Behavior corresponding to positive symptoms in humans occurred in the middle adolescence period, only in rats treated with BSO + GBR 12909. Only in the latter group, amphetamine exacerbated the existing positive symptoms in adulthood. Our data show that rats receiving the BSO + GBR 12909 combination in the early postnatal life reproduced virtually all symptoms observed in patients with schizophrenia and, therefore, can be considered a valuable neurodevelopmental model of this disease.

Keywords: effect of amphetamine; levels of BDNF mRNA and its protein; neurodevelopmental model of schizophrenia; schizophrenia-like symptoms.

Figure 1

The effect of chronic administration of BSO and GBR 12909, alone or in combination, during postnatal days p5–p16 on the social behavior assessed as the total time spent in social interactions (A) and the number of interactions (B) in adolescent and adult Sprague–Dawley rats. Data are presented as the mean ± SEM, n = 16 (8 pairs) for each group. Statistical analysis was performed using a two-way ANOVA; symbols indicate significance of differences according to the Newman–Keuls post hoc test, *** p < 0.001, ** p < 0.01, * p < 0.05 vs. control; ^### p < 0.001, ^## p < 0.01 vs. BSO- and ^∆∆∆ p < 0.001, ^∆∆ p < 0.01, ^∆ p < 0.05 vs. GBR 12909-treated groups.

Figure 2

The effect of chronic administration of BSO and GBR 12909, alone or in combination, during postnatal days p5–p16 on cognitive functions assessed in adolescent (A–C) and adult (D) Sprague–Dawley rats. (A1–D1) The effects of the studied model compounds on the exploration of two identical objects in the acquisition trials (session T1). (A2–D2) The effects of the studied model compounds on the exploration of a novel and familiar object in the retention trial (Session T2). (A3–D3) The effects of the studied model compounds on the recognition index. Data are presented as the mean ± SEM, n = 10 for each group. Letters indicate statistically significant differences between the exploration time of a novel and familiar object in the session T2 within each studied group, according to the Student’s t-test for independent samples, ^aaa p < 0.001, ^a p < 0.05 vs. familiar object. Statistical analysis of the recognition index was performed using a two-way ANOVA; symbols indicate significance of differences according to the Newman–Keuls post hoc test, *** p < 0.001, * p < 0.05 vs. control; ^### p < 0.001 vs. BSO- and ^∆∆∆ p < 0.001, ^∆ p < 0.05 vs. GBR 12909-treated groups.

Figure 3

The effect of chronic administration of BSO and GBR 12909, alone or in combination, during postnatal days p5–p16 on positive symptoms assessed in the OFT in adolescent and adult Sprague–Dawley rats as: (A) the time of walking (B) the number of sector crossings (C) the number of peeping and rearing episodes. Data are presented as the mean ± SEM, n = 10 for each group. Statistical analysis was performed using a two-way ANOVA; symbols indicate significance of differences according to the Newman–Keuls post hoc test, *** p < 0.001, ** p < 0.01, * p < 0.05 vs. control; ^### p < 0.001, ^## p < 0.01, ^# p < 0.05 vs. BSO and ^∆∆∆ p < 0.001, ^∆ p < 0.05 vs. GBR 12909-treated groups.

Figure 4

The effect of chronic administration of BSO and GBR 12909, alone or in combination, during postnatal days p5–p16, on the spontaneous and AMF-induced locomotor activity and stereotypy, measured in 90-day-old Sprague–Dawley rats using actometers. (A) Horizontal locomotor activity is presented as the total distance traveled expressed in cm, (B) vertical locomotor activity is shown as the total time spent climbing expressed in seconds (s), and (C) stereotypy as the total time devoted to stereotypical behavior expressed in seconds. These parameters were recorded during a 30–minute measurement session. Data are presented as the mean ± SEM, n = 10 for each group. Statistical analysis was performed using a two-way ANOVA; symbols indicate significance of differences according to the Newman–Keuls post hoc test, *** p < 0.001, ** p < 0.01, * p < 0.05 vs. control; ^### p < 0.001, ^# p < 0.05 vs. BSO-; and ^∆∆∆ p < 0.001, ^∆ p < 0.05 vs. GBR 12909-treated groups. Comparisons between the corresponding groups treated with saline or AMF were performed using the Student’s t-test for independent samples, ^aaa p < 0.001 vs. saline-treated control, ^bbb p < 0.001 vs. saline-treated BSO group; ^ccc p < 0.001 vs. saline-treated GBR 12909 group; ^ddd p < 0.001 vs. saline-treated BSO + GBR 12909 group.

Figure 5

The effect of chronic administration of BSO and GBR 12909, alone or in combination, during postnatal days p5–p16, on BDNF mRNA and protein levels in the PFC (A,C) and HIP (B,D) of adult rats. Data are presented as the mean ± SEM, n = 7–8 for each group. Statistical analysis was performed using a two-way ANOVA; symbols indicate significance of differences according to the Newman–Keuls post hoc test, *** p < 0.001, ** p < 0.01, * p < 0.05 vs. control; ^### p < 0.001, ^## p < 0.01, vs. BSO-; and ^∆∆∆ p < 0.001, ^∆∆ p < 0.01 vs. GBR 12909-treated groups.