Prenatal stress induces schizophrenia-like alterations of serotonin 2A and metabotropic glutamate 2 receptors in the adult offspring: role of maternal immune system

Abstract

It has been suggested that severe adverse life events during pregnancy increase the risk of schizophrenia in the offspring. The serotonin 5-HT(2A) and the metabotropic glutamate 2 (mGlu2) receptors both have been the target of considerable attention regarding schizophrenia and antipsychotic drug development. We tested the effects of maternal variable stress during pregnancy on expression and behavioral function of these two receptors in mice. Prenatal stress increased 5-HT(2A) and decreased mGlu2 expression in frontal cortex, a brain region involved in perception, cognition, and mood. This pattern of expression of 5-HT(2A) and mGlu2 receptors was consistent with behavioral alterations, including increased head-twitch response to the hallucinogenic 5-HT(2A) agonist DOI [1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane] and decreased mGlu2-dependent antipsychotic-like effect of the mGlu2/3 agonist LY379268 (1R,4R,5S,6R-2-oxa-4-aminobicyclo[3.1.0]hexane-4,6-dicarboxylate) in adult, but not prepubertal, mice born to stressed mothers during pregnancy. Cross-fostering studies determined that these alterations were not attributable to effects of prenatal stress on maternal care. Additionally, a similar pattern of biochemical and behavioral changes were observed in mice born to mothers injected with polyinosinic:polycytidylic acid [poly(I:C)] during pregnancy as a model of prenatal immune activation. These data strengthen pathophysiological hypotheses that propose an early neurodevelopmental origin for schizophrenia and other psychiatric disorders.

Figure 1.

Maternal variable stress during pregnancy affects the expression of 5-HT_2A and mGlu2 receptors in the adult offspring. A, Density of 5-HT_2A receptor shown as [³H]ketanserin binding in mouse frontal cortex (n = 11–12). B, Density of mGlu2/3 receptor shown as [³H]LY341495 binding in mouse frontal cortex (n = 9). Data are shown as percentage of specific binding in frontal cortex of adult mice born to stressed mothers relative to controls. C, Expression of mGlu2 and mGlu3 mRNA in frontal cortex determined by qRT-PCR (n = 11–12). *p < 0.05, ***p < 0.001, Student's t test. All data are presented as mean ± SEM.

Figure 2.

Exploratory activity in the open-field test. Horizontal activity (A, B) and vertical activity (C, D) in adult mice born to stressed mothers and controls. Both time course (A, C) and total counts (B, D) of the effects of maternal stress are shown (n = 32–42). n.s., Not significant, Student's t test. All data are presented as mean ± SEM.

Figure 3.

A, Head-twitch behavioral response is increased in adult mice born to stressed mothers during pregnancy. Mice were injected with DOI (0.5, 1.0, or 2.0 mg/kg), or vehicle (n = 6–10). ***p < 0.001, Bonferroni's post hoc test of two-way ANOVA. B–D, Decreased effect of LY379268 on the MK801-stimulated locomotor activity in the offspring of stressed mothers during pregnancy (C, D, white) compared with controls (B, D, black). The panels depict the time course of MK801-induced locomotion in 5 min blocks (B, C). Mice were administered LY379268 (5 mg/kg) or vehicle, followed by MK801 or vehicle. Time of injections is indicated by arrows. D, Data summary of the total MK801-induced locomotor response as a summation of horizontal activity from t = 20 to t = 120. Mice were administered LY379268 (3.0, 5.0, or 8.0 mg/kg) or vehicle, followed by MK801 or vehicle (n = 9–18 per group). *p < 0.05, Bonferroni's post hoc test of two-way ANOVA. All data are presented as mean ± SEM.

Figure 4.

A, Head-twitch behavioral response in mice prenatally unstressed and raised by control mothers, in mice prenatally exposed to maternal stress and raised by control mothers, in mice prenatally unstressed and raised by stressed mothers, and in mice prenatally exposed to maternal stress raised and by stressed mothers. Mice were injected with DOI (0.5 mg/kg) or vehicle (n = 6–8 per group). ***p < 0.001, Bonferroni's post hoc test of two-way ANOVA. B, The MK801-stimulated locomotor activity is attenuated by LY379268 (5 mg/kg) in mice prenatally unstressed and raised by stressed mothers, but it is not affected in mice prenatally stressed and raised by control mothers. Summary of the total MK801-induced locomotor response as a summation of horizontal activity from t = 20 to t = 120. Mice were administered LY379268 or vehicle, followed by MK801 or vehicle (n = 8–16 per group). *p < 0.05, ***p < 0.001, Bonferroni's post hoc test of two-way ANOVA; n.s., not significant. All data are presented as mean ± SEM.

Figure 5.

A, Density of 5-HT_2A receptor shown as [³H]ketanserin binding in frontal cortex of prepubertal (21–28 d old) mice (n = 9). B, Density of mGlu2/3 receptor density shown as [³H]LY341495 binding in frontal cortex of prepubertal mice (n = 16–18). Data are shown as percentage of specific binding in frontal cortex of prepubertal mice born to stressed mothers relative to controls. C, Head-twitch behavioral response in prepubertal mice born to stressed mothers during pregnancy. Mice were injected with DOI (0.5 mg/kg) or vehicle (n = 6–8). ***p < 0.001, Bonferroni's post hoc test of two-way ANOVA; n.s., not significant. D, The MK801-stimulated locomotor activity is attenuated by LY379268 (5 mg/kg) in control mice (black) and in prepubertal mice born to stressed mothers during pregnancy (white). Summary of the total MK801-induced locomotor response as a summation of horizontal activity from t = 20 to t = 120. Mice were administered LY379268 or vehicle, followed by MK801 or vehicle (n = 6–8 per group). ***p < 0.001, Bonferroni's post hoc test of two-way ANOVA. All data are presented as mean ± SEM.

Figure 6.

A, Density of 5-HT_2A receptor shown as [³H]ketanserin binding in frontal cortex of adult mice born to mothers injected with poly(I:C) during pregnancy (n = 14–15). B, Density of mGlu2/3 receptor density shown as [³H]LY341495 binding in frontal cortex of adult mice born to mothers injected with poly(I:C) during pregnancy (n = 9–10). Data are shown as percentage of specific binding in frontal cortex of adult mice born to mothers injected with poly(I:C) during pregnancy relative to controls. C, Head-twitch behavioral response in adult mice born to mothers injected with poly(I:C) during pregnancy. Mice were injected with DOI (0.5 mg/kg) or vehicle (n = 8). ***p < 0.001, Bonferroni's post hoc test of two-way ANOVA. D, The MK801-stimulated locomotor activity is attenuated by LY379268 (5 mg/kg) in control mice (black) and in adult mice born to mothers injected with poly(I:C) during pregnancy (white). The effect of LY379268 on the MK801-stimulated locomotor activity is decreased in adult mice born to mothers injected with poly(I:C) during pregnancy relative to controls. Summary of the total MK801-induced locomotor response as a summation of horizontal activity from t = 20 to t = 120. Mice were administered LY379268 or vehicle, followed by MK801 (n = 6 per group). *p < 0.05, **p < 0.01, Bonferroni's post hoc test of two-way ANOVA; n.s., not significant. All data are presented as mean ± SEM.

Figure 7.

Horizontal activity (A, B) and vertical activity (C, D) in adult mice born to mothers injected with poly(I:C) during pregnancy. Both time course (A, C) and total counts (B, D) of the effects of maternal stress are shown (n = 11–12). n.s., Not significant; Student's t test. All data are presented as mean ± SEM.

Figure 8.

Effect of maternal injection with poly(I:C) on choice accuracy in the discrete-trial delayed spatial alternation task. A, Animals were tested at two delay intervals: 10 and 40 s. Mice born to mothers injected with poly(I:C) during pregnancy made significantly fewer correct choices after the 40 s delay relative to the 10 s delay (n = 11–12 per group). *p < 0.05, Student's t test; n.s., not significant. B, Maternal injection with poly(I:C) during pregnancy attenuates the reversal of MK801-impaired delayed alternation memory performance (percentage of correct trials) by LY379268. Mice were administered LY379268 (5 mg/kg) or vehicle, followed by MK801 (0.5 mg/kg; n = 9–12). *p < 0.05, **p < 0.01, Bonferroni's post hoc test of two-way ANOVA; n.s., not significant. The dashed line indicates chance performance. All data are presented as mean ± SEM.