Modulation of serotonin transporter function during fetal development causes dilated heart cardiomyopathy and lifelong behavioral abnormalities

Abstract

Background: Women are at great risk for mood and anxiety disorders during their childbearing years and may become pregnant while taking antidepressant drugs. In the treatment of depression and anxiety disorders, selective serotonin reuptake inhibitors (SSRIs) are the most frequently prescribed drugs, while it is largely unknown whether this medication affects the development of the central nervous system of the fetus. The possible effects are the product of placental transfer efficiency, time of administration and dose of the respective SSRI.

Methodology/principal findings: In order to attain this information we have setup a study in which these parameters were measured and the consequences in terms of physiology and behavior are mapped. The placental transfer of fluoxetine and fluvoxamine, two commonly used SSRIs, was similar between mouse and human, indicating that the fetal exposure of these SSRIs in mice is comparable with the human situation. Fluvoxamine displayed a relatively low placental transfer, while fluoxetine showed a relatively high placental transfer. Using clinical doses of fluoxetine the mortality of the offspring increased dramatically, whereas the mortality was unaffected after fluvoxamine exposure. The majority of the fluoxetine-exposed offspring died postnatally of severe heart failure caused by dilated cardiomyopathy. Molecular analysis of fluoxetine-exposed offspring showed long-term alterations in serotonin transporter levels in the raphe nucleus. Furthermore, prenatal fluoxetine exposure resulted in depressive- and anxiety-related behavior in adult mice. In contrast, fluvoxamine-exposed mice did not show alterations in behavior and serotonin transporter levels. Decreasing the dose of fluoxetine resulted in higher survival rates and less dramatic effects on the long-term behavior in the offspring.

Conclusions: These results indicate that prenatal fluoxetine exposure affects fetal development, resulting in cardiomyopathy and a higher vulnerability to affective disorders in a dose-dependent manner.

Figure 1. Placental transfer of fluoxetine and fluvoxamine in mouse (white bars) and human (black bars) presented as mean±S.E.M.

Fluoxetine showed a high placental transfer in both mice (69%; N = 4) and human (73%; N = 6), while fluvoxamine has a low placental transfer in mice (30%; N = 4) and human (35%; N = 2).

Figure 2

(A) Survival rates of mice prenatally treated with saline (white circle), fluvoxamine (gray triangle) or fluoxetine (black square) from 1 to 20 days after birth. 81% of the fluoxetine-treated offspring died within 20 days after birth. (B) HE-staining of a horizontal section of the hearts showed dilated cardiomyopathy in fluoxetine-treated offspring. (C) Wt/r ratios of the left ventricle presented as mean±S.E.M for groups treated with saline (white bars), fluvoxamine (gray bars) and fluoxetine (black bars) at P20 (N = 6 for saline and fluvoxamine, N = 4 for fluoxetine) and adulthood (N = 5 for saline and fluvoxamine, N = 3 for fluoxetine). Wt/r = wall thickness/radius, * p<0.01.

Figure 3. Binding of 5-HTT in the raphe nucleus presented as percentage of control±S.E.M for groups treated with saline (white bars), fluvoxamine (gray bars) and fluoxetine (black bars) at P20 (A) (N = 6 for saline and fluvoxamine, N = 4 for fluoxetine) and adulthood (B) (N = 6 for saline and fluvoxamine, N = 3 for fluoxetine).

* p<0.01.

Figure 4. Behavioral data of the elevated plus maze (A, B), open field (C, D) and the novelty suppressed feeding test (E) presented as mean±S.E.M.

All behavioral test were performed with 3 groups: saline (white bars), fluvoxamine (gray bars) and fluoxetine (black bars). Panel C shows a typical example of a walking pattern in the open field (30 min) of a saline- and a fluoxetine-treated mouse. * p<0.05; ** p<0.01.

Figure 5. Survival rate and heart pathology after prenatal exposure to different doses of fluoxetine.

(A) Survival rates of mice prenatally exposed to saline (white bars), 0.3 mg/kg/day fluoxetine (light gray bars), 0.6 mg/kg/day fluoxetine (dark gray bars) and 0.8 mg/kg/day fluoxetine (black bars) measured at adulthood. 67% of the offspring exposed to the highest dose fluoxetine (0.8 mg/kg/day) died during the preweaning period as compared to 9% of the saline-treated offspring. Wt/r ratios of the left ventricle are presented mean±S.E.M for groups treated with saline (white bars; N = 5), 0.3 mg/kg/day fluoxetine (light gray bars; N = 5), 0.6 mg/kg/day fluoxetine (dark gray bars; N = 5) and 0.8 mg/kg/day fluoxetine (black bars; N = 5) at P20 (B) and adulthood (C). Wt/r = wall thickness/radius, * p<0.05; ** p<0.01.

Figure 6. Binding of 5-HTT in the raphe nucleus at adulthood expressed as percentage of control±S.E.M. for groups treated with saline (white bars), 0.3 mg/kg/day fluoxetine (light gray bars), 0.6 mg/kg/day fluoxetine (dark gray bars) and 0.8 mg/kg/day fluoxetine (black bars).

* p<0.01.

Figure 7. Behavioral data of the elevated plus maze (A, B), open field (C) and the novelty suppressed feeding test (D) presented as mean±S.E.M. for groups treated with saline (white bars), 0.3 mg/kg/day fluoxetine (light gray bars), 0.6 mg/kg/day fluoxetine (dark gray bars) and 0.8 mg/kg/day fluoxetine (black bars).

* p<0.05; ** p<0.01.