The effects of maternal depression and maternal selective serotonin reuptake inhibitor exposure on offspring

It has been estimated that 20% of pregnant women suffer from depression and it is well-documented that maternal depression can have long-lasting effects on the child. Currently, common treatment for maternal depression has been the selective serotonin reuptake inhibitor medications (SSRIs) which are used by 2–3% of pregnant women in the Nordic countries and by up to 10% of pregnant women in the United States. Antidepressants cross the placenta and are transferred to the fetus, thus, the question arises as to whether children of women taking antidepressants are at risk for altered neurodevelopmental outcomes and, if so, whether the risks are due to SSRI medication exposure or to the underlying maternal depression. This review considers the effects of maternal depression and SSRI exposure on offspring development in both clinical and preclinical populations. As it is impossible in humans to study the effects of SSRIs without taking into account the possible underlying effects of maternal depression (healthy pregnant women do not take SSRIs), animal models are of great value. For example, rodents can be used to determine the effects of maternal depression and/or perinatal SSRI exposure on offspring outcomes. Unraveling the joint (or separate) effects of maternal depression and SSRI exposure will provide more insights into the risks or benefits of SSRI exposure during gestation and will help women make informed decisions about using SSRIs during pregnancy.

Pregnancy or stress decrease complexity of CA3 pyramidal neurons in the hippocampus of adult female rats

Pregnancy is a time of distinct neural, physiological and behavioral plasticity in the female. It is also a time when a growing number of women are vulnerable to stress and experience stress-related diseases, such as depression and anxiety. However, the impact of stress during gestation on the neurobiology of the mother has yet to be determined, particularly with regard to changes in the hippocampus; a brain area that plays an important role in stress-related diseases. Therefore, the aim of the present study was to understand how stress and reproductive state may alter dendritic morphology of CA1 and CA3 pyramidal neurons in the hippocampus. To do this, adult age-matched pregnant and virgin female Wistar rats were divided into two conditions: (1) control and (2) stress. Females in the stress condition were restrained for 1h/day for the last 2 weeks of gestation and at matched time-points in virgin females. Females were sacrificed the day after the last restraint session and brains were processed for Golgi impregnation. Dendritic length and number of branch points were quantified for apical and basal regions of CA1 and CA3 pyramidal neurons. Results show that regardless of reproductive state, stressed females had significantly shorter apical dendrites and fewer apical branch points in CA3 pyramidal cells. In addition, pregnant females, regardless of stress exposure, had less complex CA3 pyramidal neurons, as measured by Sholl analysis. No differences between conditions were seen in morphology of CA1 pyramidal neurons. This work shows that both repeated restraint stress and pregnancy affect dendritic morphology by decreasing complexity of CA3, but not CA1, neurons in the hippocampus.

Pregnancy decreases oestrogen receptor alpha expression and pyknosis, but not cell proliferation or survival, in the hippocampus

Motherhood differentially affects learning and memory performance and this effect depends on reproductive experience. In turn, evidence suggests that the effects of oestradiol on learning and memory are mediated through binding to oestrogen receptors in the hippocampus and that this is related to hippocampal neurogenesis. The present study investigated the effect of pregnancy and reproductive experience on ERalpha expression throughout the hippocampus, as well as cell proliferation, new cell survival and cell death (as measured by pyknotic cells) in the granule cell layer of the hippocampus. Three groups of female Sprague-Dawley rats were used: virgin, primigravid and multigravid. All rats were injected with 5-bromo-2-deoxyuridine (BrdU; 200 mg/kg) on the afternoon of impregnation and at matched time-points in virgins. Rats were perfused either during early pregnancy (gestation day 1) or late pregnancy (gestation day 21) after BrdU injection. The results obtained show that, during late pregnancy, females, whether first or second pregnancy, have fewer ERalpha-positive cells in the CA3 region of the dorsal hippocampus than virgin females. In addition during early pregnancy, females have significantly fewer pyknotic cells in the granule cell layer than virgin females. There were no other differences between groups in the number of ERalpha-positive, BrdU-positive or pyknotic cells. Future studies will aim to investigate the mechanisms and consequences of the alteration in ERalpha expression in the hippocampus during late pregnancy, as well as the possible changes in ERbeta expression at this time.

Reproductive experience alters hippocampal neurogenesis during the postpartum period in the dam

Pregnancy and the postpartum period are a time of maximal neural and behavioral plasticity. Recent work has shown that hippocampus-dependent learning and memory performance and hippocampus morphology are affected by motherhood and reproductive experience (number of times pregnant and given birth). Adult neurogenesis in the dentate gyrus of the hippocampus is influenced by steroid hormones such as estradiol and corticosterone, which fluctuate during pregnancy and the postpartum period. Thus, it is possible that hippocampal neurogenesis may be affected by motherhood and reproductive experience. The present study aimed to investigate the role of reproductive experience on hippocampal neurogenesis via cell proliferation and cell survival and to determine whether differences were due to the effect of pregnancy and/or pup-exposure alone. Four groups of female Sprague-Dawley rats were used; multiparous, primiparous, nulliparous, and nulliparous rats exposed to pups. All rats were injected with 5-bromo-2-deoxyuridine (BrdU) (200 mg/kg) approximately 24 h after birth/pup-exposure with age-matched controls. Rats were perfused either 24 h (Expt. 1: Cell proliferation) or 21 days (Expt. 2: Cell survival) after BrdU injection. Results show there is a significant decrease in cell proliferation in the dentate gyrus of primiparous and multiparous rats during the early postpartum period, and a decrease in cell survival in the dentate gyrus during the postpartum in primiparous rats, regardless of pup-exposure, compared with all other groups. In addition, brief pup exposure to nulliparous rats significantly increased cell proliferation and cell death in the dentate gyrus, while 22 days of pup exposure to nulliparous rats (sensitized rats) resulted in increased cell survival and cell death in the dentate gyrus. Collectively these results indicate that reproductive experience significantly affects hippocampal neurogenesis and that these effects are not due to the effect of pregnancy or pup-exposure alone.