The expectant brain: adapting for motherhood

Allopregnanolone in the peripartum: Correlates, concentrations, and challenges - A systematic review

BACKGROUND

Allopregnanolone (ALLO) is a metabolite of progesterone and a neuroactive steroid hormone. As a positive allosteric modulator of gamma-aminobutyric acid (GABA) receptors, ALLO seems to have antidepressant and anxiolytic effects, and was therefore approved as a specific medication for the treatment of postpartum depression in 2019. Despite the growing number of publications investigating ALLO levels, results on the biological and psychological correlates in the peripartum period remain inconsistent, possibly due to methodological challenges regarding measurement. To date, however, there is no systematic review examining the correlates, concentrations, and challenges in measuring ALLO in peripartum women.

METHOD

A systematic literature search of PubMed and PsycINFO was conducted in August 2023. Original research articles that measured ALLO concentrations in peripartum women were included. Reports were excluded if they were not original research, included non-human subjects, did not include peripartum women, did not include ALLO measurement as an outcome, included (pharmacological) interventions, constituted method validations, or used the same cohort as another study.

RESULTS

The literature search yielded 234 articles, and two articles were identified from other sources. After full-text screening, 19 articles (N = 1401) met the inclusion criteria, of which seven focused on biological correlates of ALLO and 12 on mood correlates. Of the latter, six found no association between ALLO and mood, four found a negative association, and two found a positive association. Overall, the results show an increase in ALLO levels during pregnancy and a decrease after birth, with levels then remaining low until six months postpartum. ALLO was most commonly measured in blood plasma and by gas chromatography-mass spectrometry (GC-MS). A significant matrix effect was found for blood serum and a significant method effect for radioimmunoassays (RIAs). A significant effect of time of measurement was found.

CONCLUSION

ALLO measurement shows method and matrix effects. ALLO levels are higher when measured in serum compared to in plasma, and when measured using RIA compared to other methods. Time of measurement, study design, and standardization of measurement also influence the reliability of measurement and the interpretation of results.

The design and implementation of a multi-center, pragmatic, individual-level randomized controlled trial to evaluate Baby2Home, an mHealth intervention to support new parents

BACKGROUND

Becoming a parent is a transformative experience requiring multiple transitions, including the need to navigate several components of health care, manage any mental health issues, and develop and sustain an approach to infant feeding. Baby2Home (B2H) is a digital intervention built on the collaborative care model (CCM) designed to support families during these transitions to parenthood.

OBJECTIVES

We aim to investigate the effects of B2H on preventive healthcare utilization for the family unit and patient-reported outcomes (PROs) trajectories with a focus on mental health. We also aim to evaluate heterogeneity in treatment effects across social determinants of health including self-reported race and ethnicity and household income. We hypothesize that B2H will lead to optimized healthcare utilization, improved PROs trajectories, and reduced racial, ethnic, and income-based disparities in these outcomes as compared to usual care.

METHODS

B2H is a multi-center, pragmatic, individual-level randomized controlled trial. We will enroll 640 families who will be randomized to: [1] B2H + usual care, or [2] usual care alone. Preventive healthcare utilization is self-reported and confirmed from medical records and includes attendance at the postpartum visit, contraception use, depression screening, vaccine uptake, well-baby visit attendance, and breastfeeding at 6 months. PROs trajectories will be analyzed after collection at 1 month, 2 months, 4 months, 6 months and 12 months. PROs include assessments of stress, depression, anxiety, self-efficacy and relationship health.

IMPLICATIONS

If B2H proves effective, it would provide a scalable digital intervention to improve care for families throughout the transition to new parenthood.

THE EFFECTS OF BUPRENORPHINE AND MORPHINE DURING PREGNANCY: IMPACT OF EXPOSURE LENGTH ON MATERNAL BRAIN, BEHAVIOR, AND OFFSPRING NEURODEVELOPMENT

The escalating incidence of opioid-related issues among pregnant women in the United States underscores the critical necessity to understand the effects of opioid use and Medication for Opioid Use Disorders (MOUDs) during pregnancy. This research employed a translational rodent model to examine the impact of gestational exposure to buprenorphine (BUP) or morphine on maternal behaviors and offspring well-being. Female rats received BUP or morphine before conception, representing established use, with exposure continuing until postnatal day 2 or discontinued on gestational day 19 to mimic treatment cessation before birth. Maternal behaviors - including care, pup retrieval, and preference - as well as hunting behaviors and brain neurotransmitter levels were assessed. Offspring were evaluated for mortality, weight, length, milk bands, surface righting latency, withdrawal symptoms, and brain neurotransmitter levels. Our results reveal that regardless of exposure length (i.e., continued or discontinued), BUP resulted in reduced maternal care in contrast to morphine-exposed and control dams. Opioid exposure altered brain monoamine levels in the dams and offspring, and was associated with increased neonatal mortality, reduced offspring weight, and elevated withdrawal symptoms compared to controls. These findings underscore BUP's potential disruption of maternal care, contributing to increased pup mortality and altered neurodevelopmental outcomes in the offspring. This study calls for more comprehensive research into prenatal BUP exposure effects on the maternal brain and infant development with the aim to mitigate adverse outcomes in humans exposed to opioids during pregnancy.

Effect of high fat diet on maternal behavior, brain-derived neurotrophic factor and neural stem cell proliferation in mice expressing human placental lactogen during pregnancy

Maternal obesity is a serious health concern because it increases risks of neurological disorders, including anxiety and peripartum depression. In mice, a high fat diet (HFD) in pregnancy can negatively affect placental structure and function as well as maternal behavior reflected by impaired nest building and pup-retrieval. In humans, maternal obesity in pregnancy is associated with reduced placental lactogen (PL) gene expression, which has been linked to a higher risk of depression. PL acting predominantly through the prolactin receptor maintains energy homeostasis and is a marker of placenta villous trophoblast differentiation during pregnancy. Impaired neurogenesis and low serum levels of brain-derived neurotrophic factor (BDNF) have also been implicated in depression. Augmented neurogenesis in brain during pregnancy was reported in the subventricular zone (SVZ) of mice at gestation day 7 and linked to increased prolactin receptor signaling. Here, we used transgenic CD-1 mice that express human (h) PL during pregnancy to investigate whether the negative effects of diet on maternal behavior are mitigated in these (CD-1[hGH/PL]) mice. Specifically, we examined the effect of a HFD on nest building prepartum and pup retrieval postpartum, as well as on brain BDNF levels and neurogenesis. In contrast to wild-type CD-1[WT]mice, CD-1[hGH/PL] mice displayed significantly less anxiety-like behavior, and showed no impairment in prepartum nest building or postpartum pup-retrieval when fed a HFD. Furthermore, the HFD decreased prepartum and increased postpartum BDNF levels in CD-1[WT] but not CD-1[hGH/PL] mice. Finally, neurogenesis in the SVZ as well as phosphorylated mitogen-activated protein kinase, indicative of lactogenic signaling, appeared unaffected by pregnancy and diet at gestation day 7 in CD-1[hGH/PL] mice. These observations indicate that CD-1[hGH/PL] mice are resistant to the negative effects of HFD reported for CD-1[WT] mice, including effects on maternal behaviors and BDNF levels, and potentially, neurogenesis. This difference probably reflects a direct or indirect effect of the products of the hGH/PL transgene.

The role of prolactin in the suppression of the response to restraint stress in the lactating mouse

Suppression of the hypothalamic-pituitary-adrenal (HPA) axis is a well-characterised maternal adaptation that limits the exposure of the offspring to maternally-derived stress hormones. This current study has investigated the possible involvement of the lactogenic hormone, prolactin, in this physiologically important adaptation. As expected, circulating prolactin levels were higher in unstressed lactating mice compared to their virgin counterparts. Interestingly however, the ability of an acute period of restraint stress to further elevate prolactin levels was diminished in the former group. The stress-induced rise in prolactin levels in the virgin animals was concurrent with an increase in prolactin receptor activation within the adrenal cortical cells. This adrenal response was not seen in either the stressed or control lactation group, an observation that may be in part explained by the observed downregulation of prolactin receptor mRNA expression within this tissue. Further evidence of suppression of the HPA axis during lactation was revealed using in situ hybridisation to demonstrate that while acute restraint stress increased corticotrophin releasing hormone (CRH) mRNA expression in the hypothalamic paraventricular nucleus in both virgin and lactating mice, the magnitude of this response was reduced in the latter group. This potentially adaptive response did not, however, appear to result from the altered prolactin profile during lactation because it was not affected by the pharmacological suppression of prolactin secretion from the pituitary. This study therefore suggests that during lactation the response of the HPA axis to stress is suppressed at multiple physiological levels which are mediated by both prolactin-dependent and prolactin-independent mechanisms.

Pregnancy renders anatomical changes in hypothalamic substructures of the human brain that relate to aspects of maternal behavior

Animal studies have shown that pregnancy is associated with neural adaptations that promote maternal care. The hypothalamus represents a central structure of the mammalian maternal brain and hormonal priming of specific hypothalamic nuclei plays a key role in the induction and expression of maternal behavior. In humans, we have previously demonstrated that becoming a mother involves changes in grey matter anatomy, primarily in association areas of the cerebral cortex. In the current study, we investigated whether pregnancy renders anatomical changes in the hypothalamus. Using an advanced delineation technique, five hypothalamic substructures were defined in longitudinal MRI scans of 107 women extracted from two prospective pre-conception cohort studies, including 50 women who were scanned before and after pregnancy and 57 nulliparous control women scanned at a similar time interval. We showed that becoming a mother is associated with volume reductions in the anterior-superior, superior tuberal and posterior hypothalamus. In addition, these structural changes related to hormonal levels during pregnancy and specific aspects of self-reported maternal behavior in late pregnancy, including maternal-fetal attachment and nesting behavior. These findings show that pregnancy leads to changes in hypothalamic anatomy and suggest that these contribute to the development of maternal behavior in humans, supporting the conservation of key aspects of maternal brain circuitry and their role in maternal behavior across species.

Re-wiring of the bonded brain: Gene expression among pair bonded female prairie voles changes as they transition to motherhood

Motherhood is a costly life-history transition accompanied by behavioral and neural plasticity necessary for offspring care. Motherhood in the monogamous prairie vole is associated with decreased pair bond strength, suggesting a trade-off between parental investment and pair bond maintenance. Neural mechanisms governing pair bonds and maternal bonds overlap, creating possible competition between the two. We measured mRNA expression of genes encoding receptors for oxytocin (oxtr), dopamine (d1r and d2r), mu-opioids (oprm1a), and kappa-opioids (oprk1a) within three brain areas processing salience of sociosensory cues (anterior cingulate cortex; ACC), pair bonding (nucleus accumbens; NAc), and maternal care (medial preoptic area; MPOA). We compared gene expression differences between pair bonded prairie voles that were never pregnant, pregnant (~day 16 of pregnancy), and recent mothers (day 3 of lactation). We found greater gene expression in the NAc (oxtr, d2r, oprm1a, and oprk1a) and MPOA (oxtr, d1r, d2r, oprm1a, and oprk1a) following the transition to motherhood. Expression for all five genes in the ACC was greatest for females that had been bonded for longer. Gene expression within each region was highly correlated, indicating that oxytocin, dopamine, and opioids comprise a complimentary gene network for social signaling. ACC-NAc gene expression correlations indicated that being a mother (oxtr and d1r) or maintaining long-term pair bonds (oprm1a) relies on the coordination of different signaling systems within the same circuit. Our study suggests the maternal brain undergoes changes that prepare females to face the trade-off associated with increased emotional investment in offspring, while also maintaining a pair bond.

Adolescent stress accelerates postpartum novelty recognition impairment in 5xFAD mice

Pregnancy and the postpartum period induce physiological changes that can influence women's cognitive functions. Alzheimer's disease (AD) has a higher prevalence in women and is exacerbated by early life stress. In the present study, we found that late adolescent social isolation combined with the experience of pregnancy and delivery accelerates the onset of cognitive deficits in 5xFAD dams, particularly affecting their ability to recognize novelty. These cognitive deficits manifested as early as 16 weeks, earlier than the usual timeline for these mice, and were closely associated with increased levels of corticosterone, suggesting dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis. Notably, the presence of β-amyloid plaques in brain regions associated with novelty recognition did not significantly contribute to these deficits. This highlights the potential role of stress and HPA axis dysregulation in the development of cognitive impairments related to AD, and underscores the need for further investigation.

Neuroanatomical changes observed over the course of a human pregnancy

Pregnancy is a period of profound hormonal and physiological change experienced by millions of women annually, yet the neural changes unfolding in the maternal brain throughout gestation have not been studied in humans. Leveraging precision imaging, we mapped neuroanatomical changes in an individual from preconception through two years postpartum. Pronounced decreases in gray matter volume and cortical thickness were evident across the brain, which stand in contrast to increases in white matter microstructural integrity, ventricle volume, and cerebrospinal fluid, with few regions untouched by the transition to motherhood. This dataset serves as the first comprehensive map of the human brain across gestation, providing an open-access resource for the brain imaging community to stimulate further exploration and discovery.

Prolonged HPA axis dysregulation in postpartum depression associated with adverse early life experiences: A cross-species translational study

Childhood and adolescent stress increase the risk of postpartum depression (PPD), often providing an increased probability of treatment refractoriness. Nevertheless, the mechanisms linking childhood/adolescent stress to PPD remain unclear. Our study investigated the longitudinal effects of adolescent stress on the hypothalamic-pituitary-adrenal (HPA) axis and postpartum behaviors in mice and humans. Adolescent social isolation prolonged glucocorticoid elevation, leading to long-lasting postpartum behavioral changes in female mice. These changes were unresponsive to current PPD treatments but improved with post-delivery glucocorticoid receptor antagonist treatment. Childhood/adolescent stress significantly impacted HPA axis dysregulation and PPD in human females. Repurposing glucocorticoid receptor antagonists for some cases of treatment-resistant PPD may be considered.

Comprehensive assessment of memory function, inhibitory control, neural activity, and cortisol levels in late pregnancy

A considerable proportion of women subjectively perceive a detriment to their cognitive capacity during pregnancy, with decreased memory functions being the most frequently self-reported concerns. However, objective investigation of these perceived cognitive deficits has yielded inconsistent results. This study focused on memory functions during late pregnancy using multiple tasks designed to assess various memory indices, for example, working memory, learning rate, immediate recall, proactive and retroactive interference, delayed recall, retrieval efficiency, visuospatial constructional ability, recognition, and executive function. Additionally, sustained attention and inhibitory control were examined using a combined recognition stop-signal task. Electrophysiological brain activity during this task was recorded using a 128-channel electroencephalographic-event-related potential system. Salivary cortisol levels were assessed both prior to and following the experimental session. In contrast to the widely held belief, results demonstrated that women in late pregnancy did not exhibit a decline in their performance across the various memory tests. In terms of accuracy, there was not a single task in which poorer performance was found for pregnant women. The quality of memory performance was comparable, and in some cases even superior, among women in the pregnancy group. On the stop-signal task, pregnant women exhibited significantly better performance, and their electrophysiological data revealed greater centrally distributed P300 amplitude to "stop" signs, which may signify an enhanced neural efficiency in the domains of inhibitory executive control. Endocrine results revealed that pregnant women exhibited significantly lower levels of salivary cortisol, suggesting an attenuation of hypothalamic-pituitary-adrenocortical axis activity, which may contribute to the optimization of fetal development and growth.

Neurobiological mechanisms underlying oxytocin-mediated parental behavior in rodents

Parental behavior is essential for mammalian offspring to survive. Because of this significance, elucidating the neurobiological mechanisms that facilitate parental behavior has received strong interest. Decades of studies utilizing pharmacology and molecular biology have revealed that in addition to its facilitatory effects on parturition and lactation, oxytocin (OT) promotes the expression of parental behavior in rodents. Recent studies have also described the modulation of sensory processing by OT and the interaction of the OT system with other brain regions associated with parental behavior. However, the precise neurobiological mechanisms underlying the facilitation of caregiving behaviors by OT remain unclear. In this Review, I summarize the findings from rats and mice with a view toward integrating past and recent progress. I then review recent advances in the understanding of the molecular, cellular, and circuit mechanisms of OT-mediated parental behavior. Based on these observations, I propose a hypothetical model that would explain the mechanisms underlying OT-mediated parental behavior. Finally, I conclude by discussing some major remaining questions and propose potential future research directions.

Do Parental Hormone Levels Synchronize During the Prenatal and Postpartum Periods? A Systematic Review

Physiological synchrony is the phenomenon of linked physiological processes among two or more individuals. Evidence of linkage between dyads has been found among a broad range of physiological indices, including the endocrine systems. During the transition to parenthood, both men and women undergo hormonal changes that facilitate parenting behavior. The present review sought to address the question as to whether hormonal synchronization occurs among expecting or new parents. A systematic literature search yielded 13 eligible records. The evidence of cortisol synchrony during the prenatal period, with additional testosterone, prolactin, and progesterone covariations in the time leading up to childbirth, was found to be most significant. During the postpartum period, parental synchrony was reported for oxytocin, testosterone, and cortisol levels. The implications of these covariations were found to translate into adaptive parenting behaviors and the facilitation of romantic bond. Associations with infant development were also reported, suggesting far-reaching effects of hormonal synchrony outside the parental dyad. The results highlight the importance of physiological interrelatedness during this sensitive period, underscoring the need for further research in this field. In view of the limited data available in this research domain, we have put forward a framework for future studies, recommending the adoption of standardized research protocols and repeated collections of specimens.

How is prenatal stress transmitted from the mother to the fetus?

Prenatal stress programmes long-lasting neuroendocrine and behavioural changes in the offspring. Often this programming is maladaptive and sex specific. For example, using a rat model of maternal social stress in late pregnancy, we have demonstrated that adult prenatally stressed male, but not prenatally stressed female offspring display heightened anxiety-like behaviour, whereas both sexes show hyperactive hypothalamo-pituitary-adrenal (HPA) axis responses to stress. Here, we review the current knowledge of the mechanisms underpinning dysregulated HPA axis responses, including evidence supporting a role for reduced neurosteroid-mediated GABAergic inhibitory signalling in the brains of prenatally stressed offspring. How maternal psychosocial stress is signalled from the mother to the fetuses is unclear. Direct transfer of maternal glucocorticoids to the fetuses is often considered to mediate the programming effects of maternal stress on the offspring. However, protective mechanisms including attenuated maternal stress responses and placental 11β-hydroxysteroid dehydrogenase-2 (which inactivates glucocorticoids) should limit materno-fetal glucocorticoid transfer during pregnancy. Moreover, a lack of correlation between maternal stress, circulating maternal glucocorticoid levels and circulating fetal glucocorticoid levels is reported in several studies and across different species. Therefore, here we interrogate the evidence for a role for maternal glucocorticoids in mediating the effects of maternal stress on the offspring and consider the evidence for alternative mechanisms, including an indirect role for glucocorticoids and the contribution of changes in the placenta in signalling the stress status of the mother to the fetus.

Letter to the Editor: Does fetal movement shape the maternal brain?

Here, we debate that fetal behavior may contribute to the dynamic changes observed in the maternal brain during the perinatal period. We call for future research to explore this perspective to understand the complex maternal-fetal relationship and how fetal signals influence the preparation for parenthood.

Effects of reproductive experience on cost-benefit decision making in female rats

Many individuals undergo mating and/or other aspects of reproductive experience at some point in their lives, and pregnancy and childbirth in particular are associated with alterations in the prevalence of several psychiatric disorders. Research in rodents shows that maternal experience affects spatial learning and other aspects of hippocampal function. In contrast, there has been little work in animal models concerning how reproductive experience affects cost-benefit decision making, despite the relevance of this aspect of cognition for psychiatric disorders. To begin to address this issue, reproductively experienced (RE) and reproductively naïve (RN) female Long-Evans rats were tested across multiple tasks that assess different forms of cost-benefit decision making. In a risky decision-making task, in which rats chose between a small, safe food reward and a large food reward accompanied by variable probabilities of punishment, RE females chose the large risky reward significantly more frequently than RN females (greater risk taking). In an intertemporal choice task, in which rats chose between a small, immediate food reward and a large food reward delivered after a variable delay period, RE females chose the large reward less frequently than RN females. Together, these results show distinct effects of reproductive experience on different forms of cost-benefit decision making in female rats, and highlight reproductive status as a variable that could influence aspects of cognition relevant for psychiatric disorders.

Gustatory and olfactory shifts during pregnancy and the postpartum period: A systematic review and meta-analysis

Pregnancy is a transformative phase marked by significant behavioral and physiological changes. Substantial changes in pregnancy-related hormones are thought to induce changes in chemosensory perception, as often observed in non-human animals. However, empirical behavioral research on pregnancy-related olfactory or gustatory changes has not yet reached a consensus. This PROSPERO pre-registered systematic review and meta-analysis evaluated published data of olfactory and gustatory changes in pregnant individuals, across the three pregnancy trimesters and postpartum period. Our comprehensive search strategy identified 20 relevant studies, for inclusion in the meta-analysis. The meta-analysis revealed that pregnant individuals, regardless of trimester, performed significantly poorer in terms of odour identification, however, no difference was detected between non-pregnant controls and women postpartum. Additionally, pregnant women in the second and third trimester rated olfactory stimuli to be more intense. A slight decline in odour pleasantness ratings was observed amongst those in the second trimester. No major difference was observed between pregnant and non-pregnant subjects in terms of gustatory functions, except the first trimester appeared to be associated with increased pleasantness for the sweet taste. Post-hoc meta-regression analyses revealed that pregnancy stage was a significant predictor for observed effect size for odour intensity ratings, but not for odour identification scores. These findings provide valuable insights into the interplay between pregnancy and chemosensory perception, highlighting systematic physiological changes due to pregnancy. Healthcare providers can also utilize the knowledge of sensory shifts to better support pregnant women in making appropriate dietary choices, managing sense-related discomfort, and leading to potential sensory interventions. Overall, this research enhances our comprehension of sensory shifts during pregnancy, benefiting maternal health and pregnancy-related care.

Mitochondrial might: powering the peripartum for risk and resilience

The peripartum period, characterized by dynamic hormonal shifts and physiological adaptations, has been recognized as a potentially vulnerable period for the development of mood disorders such as postpartum depression (PPD). Stress is a well-established risk factor for developing PPD and is known to modulate mitochondrial function. While primarily known for their role in energy production, mitochondria also influence processes such as stress regulation, steroid hormone synthesis, glucocorticoid response, GABA metabolism, and immune modulation - all of which are crucial for healthy pregnancy and relevant to PPD pathology. While mitochondrial function has been implicated in other psychiatric illnesses, its role in peripartum stress and mental health remains largely unexplored, especially in relation to the brain. In this review, we first provide an overview of mitochondrial involvement in processes implicated in peripartum mood disorders, underscoring their potential role in mediating pathology. We then discuss clinical and preclinical studies of mitochondria in the context of peripartum stress and mental health, emphasizing the need for better understanding of this relationship. Finally, we propose mitochondria as biological mediators of resilience to peripartum mood disorders.

Maternal care behavior and physiology moderate offspring outcomes following gestational exposure to opioids

The opioid epidemic has resulted in a drastic increase in gestational exposure to opioids. Opioid-dependent pregnant women are typically prescribed medications for opioid use disorders ("MOUD"; e.g., buprenorphine [BUP]) to mitigate the harmful effects of abused opioids. However, the consequences of exposure to synthetic opioids, particularly BUP, during gestation on fetal neurodevelopment and long-term outcomes are poorly understood. Further, despite the known adverse effects of opioids on maternal care, many preclinical and clinical studies investigating the effects of gestational opioid exposure on offspring outcomes fail to report on maternal care behaviors. Considering that offspring outcomes are heavily dependent upon the quality of maternal care, it is important to evaluate the effects of gestational opioid exposure in the context of the mother-infant dyad. This review compares offspring outcomes after prenatal opioid exposure and after reduced maternal care and integrates this information to potentially identify common underlying mechanisms. We explore whether adverse outcomes after gestational BUP exposure are due to direct effects of opioids in utero, deficits in maternal care, or a combination of both factors. Finally, suggestions for improving preclinical models of prenatal opioid exposure are provided to promote more translational studies that can help to improve clinical outcomes for opioid-dependent mothers.

Long noncoding RNA NONHSAG045500 regulates serotonin transporter to ameliorate depressive-like behavior via the cAMP-PKA-CREB signaling pathway in a model of perinatal depression

OBJECTIVE

Perinatal depression (PND) is the most common complication of childbirth and negatively affects the mother. Long noncoding RNA (lncRNA) NONHSAG045500 inhibits the expression of 5-hydroxytryptamine (5-HT) transporter (i.e. serotonin transporter [SERT]) and produces an antidepressant effect. This study aimed to identify a link between the lncRNA NONHSAG045500 and the pathogenesis of PND.

METHODS

Female C57BL/6 J mice were divided into normal control group (control group, n = 15), chronic unpredictable stress (CUS) model group (PND group, n = 15), lncRNA NONHSAG045500-overexpressed group (LNC group, sublingual intravenous injection of NONHSAG045500 overexpression cells for 7 days, n = 15), and escitalopram treatment group (i.e. the selective serotonin reuptake inhibitor [SSRI] group, with escitalopram administered from the 10th day after pregnancy to the 10th day after delivery, n = 15). Control group mice were conceived normally, whereas, in the other groups, a CUS model was established before mice were conceived. Depressive-like behaviour was assessed via sucrose preference, forced swimming, and open-field tests. The expression levels of 5-HT, SERT, and cAMP-PKA-CREB pathway-related proteins in the prefrontal cortex were detected on the 10th day after delivery.

RESULTS

Mice in the PND group exhibited significant depressive-like behaviours compared with those in the control group, indicating that the PND model was successfully established. The expression of lncRNA NONHSAG045500 was markedly decreased in the PND group compared with that in the control group. After treatment, both LNC and SSRI groups showed a significant improvement in depression-like behaviour, and the expression of 5-HT in the prefrontal cortex was increased in these groups compared with that in the PND group. In addition, the LNC group displayed lower expression of SERT and higher expression of cAMP, PKA, and CREB when in comparison to PND group.

CONCLUSION

NONHSAG045500 mediates the development of PND mainly by activating the cAMP-PKA-CREB pathway, increasing the level of 5-HT, and decreasing the expression of SERT.

Microglia depletion facilitates the display of maternal behavior and alters activation of the maternal brain network in nulliparous female rats

The peripartum period is accompanied by peripheral immune alterations to promote a successful pregnancy. We and others have also demonstrated significant neuroimmune changes that emerge during late pregnancy and persist postpartum, most prominently decreased microglia numbers within limbic brain regions. Here we hypothesized that microglial downregulation is important for the onset and display of maternal behavior. To test this, we recapitulated the peripartum neuroimmune profile by depleting microglia in non-mother (i.e., nulliparous) female rats who are typically not maternal but can be induced to behave maternally towards foster pups after repeated exposure, a process called maternal sensitization. BLZ945, a selective colony-stimulating factor 1 receptor (CSF1R) inhibitor, was administered systemically to nulliparous rats, which led to ~75% decrease in microglia number. BLZ- and vehicle-treated females then underwent maternal sensitization and tissue was stained for ∆fosB to examine activation across maternally relevant brain regions. We found BLZ-treated females with microglial depletion met criteria for displaying maternal behavior significantly sooner than vehicle-treated females and displayed increased pup-directed behaviors. Microglia depletion also reduced threat appraisal behavior in an open field test. Notably, nulliparous females with microglial depletion had decreased numbers of ∆fosB+ cells in the medial amygdala and periaqueductal gray, and increased numbers in the prefrontal cortex and somatosensory cortex, compared to vehicle. Our results demonstrate that microglia regulate maternal behavior in adult females, possibly by shifting patterns of activity in the maternal brain network.

Monitoring oxytocin signaling in the brain: More than a love story

More than any other neuropeptide, oxytocin (OXT) is attracting the attention of neurobiologists, psychologists, psychiatrists, evolutionary biologists and even economists. It is often called a "love hormone" due to its many prosocial functions described in vertebrates including mammals and humans, especially its ability to support "bonding behaviour". Oxytocin plays an important role in female reproduction, as it promotes labour during parturition, enables milk ejection in lactation and is essential for related reproductive behaviours. Therefore, it particularly attracts the interest of many female researchers. In this short narrative review I was invited to provide a personal overview on my scientific journey closely linked to my research on the brain OXT system and the adventures associated with starting my research career behind the Iron Curtain.

Association between parental behaviors and structural plasticity in the brain of male rodents

In recent decades, human fathers across the globe have shown a substantial increase in their engagement in paternal caregiving behaviors. Despite the growing interest, the precise neurobiological mechanisms underlying caregiving behaviors in males remain unclear. Neurobiological studies conducted on rodents have advanced our understanding of the molecular, cellular, and circuit-level mechanisms. Typically, sexually naïve males exhibit aggression toward offspring, while fathers display parental behaviors. This drastic behavioral plasticity may be associated with changes in connections among specific regions or cell types. Recent studies have begun to describe this structural plasticity by comparing neural connections before and after fatherhood. In this Perspective, we summarize the findings from four well-studied rodent species, namely prairie voles, California mice, laboratory rats, and laboratory mice, with a view toward integrating past and current progress. We then review recent advances in the understanding of structural plasticity for parental behaviors. Finally, we discuss remaining questions that require further exploration to gain a deeper understanding of the neural mechanisms underlying paternal behaviors in males, including their possible implications for the human brain.

Compensatory enhancement of paternal care in maternally neglected mice family

Parental care strategies, ranging from biparental to uniparental, evolve based on factors affecting sexual conflict over care. Plasticity in how parents respond to reduction in each other's care effort is thus proposed to be important in the evolution of parental care behaviors. Models predict that 'obligate' biparental care is stable when a parent responds to reduced partner effort with 'partial' compensation, trading-off current and future reproduction. A meta-analysis of experimental studies on biparental birds also revealed partial compensation, supporting coevolution of parental care type and plasticity pattern. However, few studies have addressed this issue across different taxa and different parental care types. In laboratory mice, a female-biased 'facultative' biparental species, fathers paired with a competent mother rarely provide care. We show that, when mated with a pup-neglecting mutant mother, fathers increased care effort to 'fully' compensate for the lost maternal care in both pup survival rate and total care amount. Pup retrieval latency was significantly shorter, and neural activity in relevant brain regions twice as high, suggesting enhanced motivation. This study with mice not only opens a road to explore the neural correlates of paternal plasticity but will also help understand how behavioral plasticity contributes to adaptive evolution of parental care behaviors.

Hormone-mediated neural remodeling orchestrates parenting onset during pregnancy

During pregnancy, physiological adaptations prepare the female body for the challenges of motherhood. Becoming a parent also requires behavioral adaptations. Such adaptations can occur as early as during pregnancy, but how pregnancy hormones remodel parenting circuits to instruct preparatory behavioral changes remains unknown. We found that action of estradiol and progesterone on galanin (Gal)-expressing neurons in the mouse medial preoptic area (MPOA) is critical for pregnancy-induced parental behavior. Whereas estradiol silences MPOAGal neurons and paradoxically increases their excitability, progesterone permanently rewires this circuit node by promoting dendritic spine formation and recruitment of excitatory synaptic inputs. This MPOAGal-specific neural remodeling sparsens population activity in vivo and results in persistently stronger, more selective responses to pup stimuli. Pregnancy hormones thus remodel parenting circuits in anticipation of future behavioral need.

Cannabis use during pregnancy and hemodynamic responses to infant cues in pregnancy: an exploratory study

Introduction

Cannabis is one of the most commonly used substances during pregnancy and has the potential to negatively impact parent-infant relationships. The prefrontal cortex (PFC) response to infant cues during pregnancy has been associated with subsequent positive parenting behaviors. However, PFC activation is altered in individuals who use cannabis. As the potency of cannabis has changed over the years, little is known about the specific role of cannabis use on gestational parent brain responses to infant cues.

Materials and methods

Using functional Near-Infrared Spectroscopy (fNIRS) in the second trimester of pregnancy, we measured hemodynamic responses to an infant cry task and an infant faces task among individuals who were using cannabis (N = 14) and compared them with those who were not using cannabis (N = 45). For the infant cry task, pregnant individuals listened to cry sounds and matched white noise. For the infant faces task, they viewed happy, sad, and neutral faces.

Results

There was no significant difference between the two groups after adjusting for multiple comparisons. Without adjusting for multiple comparisons, we found preliminary evidence for the differences in the dorsomedial PFC associated with heightened response to infant cry among individuals who use cannabis. The groups were also different in the dorsolateral PFC associated with decreased response to infant sad faces among individuals who use cannabis.

Discussion

Our preliminary data suggests that cannabis use during pregnancy was associated with brain activation in the regions involved in the emotional regulation and information processes. However, the results did not survive after adjustment for multiple comparisons, thus future research with larger sample sizes is needed to confirm potential differences in brain function among cannabis-using pregnant individuals.

Interaction of the pre- and postnatal environment in the maternal immune activation model

Adverse influences during pregnancy are associated with a range of unfavorable outcomes for the developing offspring. Maternal psychosocial stress, exposure to infections and nutritional imbalances are known risk factors for neurodevelopmental derangements and according psychiatric and neurological manifestations later in offspring life. In this context, the maternal immune activation (MIA) model has been extensively used in preclinical research to study how stimulation of the maternal immune system during gestation derails the tightly coordinated sequence of fetal neurodevelopment. The ensuing consequence of MIA for offspring brain structure and function are majorly manifested in behavioral and cognitive abnormalities, phenotypically presenting during the periods of adolescence and adulthood. These observations have been interpreted within the framework of the "double-hit-hypothesis" suggesting that an elevated risk for neurodevelopmental disorders results from an individual being subjected to two adverse environmental influences at distinct periods of life, jointly leading to the emergence of pathology. The early postnatal period, during which the caregiving parent is the major determinant of the newborn´s environment, constitutes a window of vulnerability to external stimuli. Considering that MIA not only affects the developing fetus, but also impinges on the mother´s brain, which is in a state of heightened malleability during pregnancy, the impact of MIA on maternal brain function and behavior postpartum may importantly contribute to the detrimental consequences for her progeny. Here we review current information on the interaction between the prenatal and postnatal maternal environments in the modulation of offspring development and their relevance for the pathophysiology of the MIA model.

Biosynthesis and Function of VIP and Oxytocin: Mechanisms of C-terminal Amidation, Oxytocin Secretion and Transport

In this review, we provide the status of research on vasoactive intestinal peptide (VIP) and oxytocin, typical C-terminal α-amidated peptide hormones, including their precursor protein structures, processing and C-terminal α-amidation, and the recently identified mechanisms of regulation of oxytocin secretion and its transportation through the blood brain barrier. More than half of neural and endocrine peptides, such as VIP and oxytocin, have the α-amide structure at their C-terminus, which is essential for biological activities. We have studied the synthesis and function of C-terminal α-amidated peptides, including VIP and oxytocin, since the 1980s. Human VIP mRNA encoded not only VIP but also another related C-terminal α-amidated peptide, PHM-27 (peptide having amino-terminal histidine, carboxy-terminal methionine amide, and 27 amino acid residues). The human VIP/PHM-27 gene is composed of 7 exons and regulated synergistically by cyclic AMP and protein kinase C pathways. VIP has an essential role in glycemic control using transgenic mouse technology. The peptide C-terminal α-amidation proceeded through a 2-step mechanism catalyzed by 2 different enzymes encoded in a single mRNA. In the oxytocin secretion from the hypothalamus/the posterior pituitary, the CD38-cyclic ADP-ribose signal system, which was first established in the insulin secretion from pancreatic β cells of the islets of Langerhans, was found to be essential. A possible mechanism involving RAGE (receptor for advanced glycation end-products) of the oxytocin transportation from the blood stream into the brain through the blood-brain barrier has also been suggested.

The Impact of Mild Chronic Stress and Maternal Experience in the Fmr1 Mouse Model of Fragile X Syndrome

Fragile X syndrome (FXS) is a pervasive developmental disorder and the most common monogenic cause of autism spectrum disorder (ASD). Female heterozygous (HET) carriers play a major role in the transmission of the pathology and present several FXS- and ASD-like behavioral alterations. Despite their clear genetic origins, FXS symptoms are known to be modulated by environmental factors, e.g., exposure to chronic stress, especially during critical life periods, such as pregnancy. Pregnancy, together with pups' care, constitutes maternal experience, i.e., another powerful environmental factor affecting several neurobehavioral functions in females. Here we investigated the impact of maternal experience on the long-term effects of stress in Fmr1-HET female mice. Our findings demonstrated that the behavioral abnormalities of HET females, i.e., hyperactivity and memory deficits, were unaffected by stress or maternal experience. In contrast, stress, independently of maternal experience, induced the appearance of cognitive deficits in WT mice. Maternal experience increased anxiety levels in all mice and enhanced their corticosterone levels, concomitantly promoting the effects of stress on social communication and adrenal glands. In translational terms, these results advance our understanding of the environmental modulation of the behavioral alterations observed in FXS female carriers and highlight the long-term impact of maternal experience and its interactions with chronic stress.

Adolescent stress impairs postpartum social behavior via anterior insula-prelimbic pathway in mice

Adolescent stress can be a risk factor for abnormal social behavior in the postpartum period, which critically affects an individual social functioning. Nonetheless, the underlying mechanisms remain unclear. Using a mouse model with optogenetics and in vivo calcium imaging, we found that adolescent psychosocial stress, combined with pregnancy and delivery, caused hypofunction of the glutamatergic pathway from the anterior insula to prelimbic cortex (AI-PrL pathway), which altered PrL neuronal activity, and in turn led to abnormal social behavior. Specifically, the AI-PrL pathway played a crucial role during recognizing the novelty of other mice by modulating "stable neurons" in PrL, which were constantly activated or inhibited by novel mice. We also observed that glucocorticoid receptor signaling in the AI-PrL pathway had a causal role in stress-induced postpartum changes. Our findings provide functional insights into a cortico-cortical pathway underlying adolescent stress-induced postpartum social behavioral deficits.

Adolescent stress impairs postpartum social behavior via anterior insula-prelimbic pathway

Adolescent stress can be a risk factor for abnormal social behavior in the postpartum period, which critically affects the safety of mothers and children. Nonetheless, the underlying mechanisms remain unclear. Using a newly established mouse model with optogenetics and in vivo calcium imaging, we found that adolescent psychosocial stress, combined with pregnancy and delivery, caused hypofunction of the glutamatergic pathway from the anterior insula to prelimbic cortex (AI-PrL pathway), which altered PrL neuronal activity, and in turn led to abnormal social behavior. Specifically, the AI-PrL pathway played a crucial role during recognizing the novelty of other mice by modulating ″stable neurons″ in PrL, which were constantly activated or inhibited by novel mice. We also observed that glucocorticoid receptor signaling in the AI-PrL pathway had a causal role in stress-induced postpartum changes. Our findings provide novel and functional insights into a cortico-cortical pathway underlying adolescent stress-induced postpartum social behavioral deficits.

Increased depressive-like behaviour of postpartum Flinders sensitive and resistant line rats is reversed by a predictable postpartum stressor

During the peripartum period, women are at an increased risk to develop perinatal distress, presenting as symptoms of depression and/or anxiety. Yet, due to practical and ethical restrictions, our understanding of this condition remains limited. Animal studies that focus on the neuropsychiatric mechanisms associated with the postpartum period, often ignore the genetical predisposition factor. We therefore investigated whether pregnancy could alter the bio-behavioural profile of the Flinders sensitive and resistant line rats, and whether these effects are exacerbated by a postpartum stressor. Postpartum dams were compared to nulliparous controls in behavioural tests, analysing depressive- and anxiety-like behaviours. Next, postpartum dams were subjected to a maternal separation and early weaning (MSEW) regimen, with their behaviour and serotonergic and noradrenergic concentrations compared to rats not separated from their pups. Regardless of strain, pregnancy decreased time spent in the open arms of the elevated plus maze and hippocampal serotonin concentrations. Time spent immobile in the forced swim test was also increased, with a significant effect in the FRL and a strong trend in the FSL rats. MSEW reversed these behaviours in both strains and increased social interaction with a male counterpart in the FSL rats, without influencing hippocampal or cortical serotonin or norepinephrine. Taken together, these results suggest that pregnancy influences postpartum behaviour, in a strain-dependent manner. Contrary to what we expected, MSEW overall decreased depressive- and anxiety-like behaviours, with strain specific differences, indicating that a chronic, predictable stressor may not necessarily adversely affect postpartum behaviour.

Matrescence: lifetime impact of motherhood on cognition and the brain

Profound environmental, hormonal, and neurobiological changes mark the transition to motherhood as a major biosocial life event. Despite the ubiquity of motherhood, the enduring impact of caregiving on cognition and the brain across the lifespan is not well characterized and represents a unique window of opportunity to investigate human neural and cognitive development. By integrating insights from the human and animal maternal brain literatures with theories of cognitive ageing, we outline a framework for understanding maternal neural and cognitive changes across the lifespan. We suggest that the increased cognitive load of motherhood provides an initial challenge during the peripartum period, requiring continuous adaptation; yet when these demands are sustained across the lifespan, they result in increased late-life cognitive reserve.

Maternity Blues: A Narrative Review

Puerperium is a period of great vulnerability for the woman, associated with intense physical and emotional changes. Maternity blues (MB), also known as baby blues, postnatal blues, or post-partum blues, include low mood and mild, transient, self-limited depressive symptoms, which can be developed in the first days after delivery. However, the correct identification of this condition is difficult because a shared definition and well-established diagnostic tools are not still available. A great heterogenicity has been reported worldwide regarding MB prevalence. Studies described an overall prevalence of 39%, ranging from 13.7% to 76%, according to the cultural and geographical contexts. MB is a well-established risk factor for shifting to more severe post-partum mood disorders, such as post-partum depression and postpartum psychosis. Several risk factors and pathophysiological mechanisms which could provide the foundation of MB have been the object of investigations, but only poor evidence and speculations are available until now. Taking into account its non-negligible prevalence after childbirth, making an early diagnosis of MB is important to provide adequate and prompt support to the mother, which may contribute to avoiding evolutions toward more serious post-partum disorders. In this paper, we aimed to offer an overview of the knowledge available of MB in terms of definitions, diagnosis tools, pathophysiological mechanisms, and all major clinical aspects. Clinicians should know MB and be aware of its potential evolutions in order to offer the most timely and effective evidence-based care.

Functional near-infrared spectroscopy is a useful tool for multi-perspective psychobiological study of neurophysiological correlates of parenting behaviour

The quality of the relationship between caregiver and child has long-term effects on the cognitive and socio-emotional development of children. A process involved in human parenting is the bio-behavioural synchrony that occurs between the partners in the relationship during interaction. Through interaction, bio-behavioural synchronicity allows the adaptation of the physiological systems of the parent to those of the child and promotes the positive development and modelling of the child's social brain. The role of bio-behavioural synchrony in building social bonds could be investigated using functional near-infrared spectroscopy (fNIRS). In this paper we have (a) highlighted the importance of the quality of the caregiver-child relationship for the child's cognitive and socio-emotional development, as well as the relevance of infantile stimuli in the activation of parenting behaviour; (b) discussed the tools used in the study of the neurophysiological substrates of the parental response; (c) proposed fNIRS as a particularly suitable tool for the study of parental responses; and (d) underlined the need for a multi-systemic psychobiological approach to understand the mechanisms that regulate caregiver-child interactions and their bio-behavioural synchrony. We propose to adopt a multi-system psychobiological approach to the study of parental behaviour and social interaction.

An accessory prefrontal cortex-thalamus circuit sculpts maternal behavior in virgin female mice

The ability to care for the young is innate and readily displayed by postpartum females after delivery to ensure offspring survival. Upon pup exposure, rodent virgin (nulliparous) females also develop parental behavior that over time becomes displayed at levels equivalent to parenting mothers. Although maternal behavior in postpartum females and the associated neurocircuits are well characterized, the neural mechanisms underlying the acquisition of maternal behavior without prior experience remain poorly understood. Here, we show that the development of maternal care behavior in response to first-time pup exposure in virgin females is initiated by the activation of the anterior cingulate cortex (ACC). ACC activity is dependent on feedback excitation by Vglut2+ /Galanin+ neurons of the centrolateral nucleus of the thalamus (CL), with their activity sufficient to display parenting behaviors. Accordingly, acute bidirectional chemogenetic manipulation of neuronal activity in the ACC facilitates or impairs the attainment of maternal behavior, exclusively in virgin females. These results reveal an ACC-CL neurocircuit as an accessory loop in virgin females for the initiation of maternal care upon first-time exposure to pups.

Mapping the effects of pregnancy on resting state brain activity, white matter microstructure, neural metabolite concentrations and grey matter architecture

While animal studies have demonstrated a unique reproduction-related neuroplasticity, little is known on the effects of pregnancy on the human brain. Here we investigated whether pregnancy is associated with changes to resting state brain activity, white matter microstructure, neural metabolite concentrations and grey matter architecture using a comprehensive pre-conception cohort study. We show that pregnancy leads to selective and robust changes in neural architecture and neural network organization, which are most pronounced in the Default Mode Network. These neural changes correlated with pregnancy hormones, primarily third-trimester estradiol, while no associations were found with other factors such as osmotic effects, stress and sleep. Furthermore, the changes related to measures of maternal-fetal bonding, nesting behavior and the physiological responsiveness to infant cues, and predicted measures of mother-infant bonding and bonding impairments. These findings suggest there are selective pregnancy-related modifications in brain structure and function that may facilitate peripartum maternal processes of key relevance to the mother-infant dyad.

Abnormal maternal behavior in mice lacking phospholipase Cβ1

Motherhood goes through preparation, onset and maintenance phases until the natural weaning. A variety of changes in hormonal/neurohormonal systems and brain circuits are involved in the maternal behavior. Hormones, neuropeptides, and neurotransmitters involved in maternal behavior act via G-protein-coupled receptors, many of which in turn activate plasma membrane enzymes including phospholipase C (PLC) β isoforms. In this study, we examined the effect of PLCβ1 knockout (KO) on maternal behavior. There was little difference between PLCβ1-KO and wild-type (WT) dams in the relative time spent in maternal behavior during the period between 24 h prepartum and 12 h postpartum (-24 h ∼ PPH 12). After PPH 18, however, PLCβ1-KO dams neglected their pups so that they all died in 2-3 days. In the pup retrieval test, latency was not different during the period within PPH 12, but after PPH 18, PLCβ1-KO dams could not finish pup retrieval in a given time. During both periods, FosB expression in the nucleus accumbens (NAcc) of PLCβ1-KO dams was significantly lower than WT, but not different in the medial preoptic area (mPOA). Given that mPOA activity is required for initiation of maternal behavior, and that NAcc is known to be involved in maternal motivation and maintenance of maternal behavior, our results suggest that PLCβ1 signaling is essential for transition from the onset to maintenance phase of maternal behavior.

Hormonal and behavioral responses to an infant simulator in women with and without children

We investigated the impact of maternal status on hormonal reactivity and behavioral responses to an infant simulator in 117 women (54 primiparous, 63 nulliparous). The amount of affectionate touch and motherese were analyzed as behavioral measures of caregiving. Saliva was collected before and 10 min after interaction with the infant simulator to analyze oxytocin, testosterone, cortisol, and estradiol levels. Nulliparous women also provided information about their fertility motivation. Linear mixed models indicated that greater use of affectionate touch was associated with lower overall testosterone levels. Cortisol decreased in response to the interaction in both groups. In the primiparous group, the amount of affectionate touch associated inversely with cortisol levels, whereas in the nulliparous group such association was not found. Oxytocin or estradiol reactivity to the simulator did not differ between the groups, nor were these hormones associated with behavior. Higher fertility motivation in nulliparous women was related to more motherese, and lower testosterone levels. Our results indicate that the simulator elicits hormonal reactivity both in mothers and nonmothers, but the patterns of associations between caregiving behavior and hormonal levels may be partially different. These results encourage using the infant simulator to explore hormonal processes related to the transition to parenthood.

Ovarian steroid hormones: A long overlooked but critical contributor to brain aging and Alzheimer's disease

Ovarian hormones, particularly 17β-estradiol, are involved in numerous neurophysiological and neurochemical processes, including those subserving cognitive function. Estradiol plays a key role in the neurobiology of aging, in part due to extensive interconnectivity of the neural and endocrine system. This aspect of aging is fundamental for women's brains as all women experience a drop in circulating estradiol levels in midlife, after menopause. Given the importance of estradiol for brain function, it is not surprising that up to 80% of peri-menopausal and post-menopausal women report neurological symptoms including changes in thermoregulation (vasomotor symptoms), mood, sleep, and cognitive performance. Preclinical evidence for neuroprotective effects of 17β-estradiol also indicate associations between menopause, cognitive aging, and Alzheimer's disease (AD), the most common cause of dementia affecting nearly twice more women than men. Brain imaging studies demonstrated that middle-aged women exhibit increased indicators of AD endophenotype as compared to men of the same age, with onset in perimenopause. Herein, we take a translational approach to illustrate the contribution of ovarian hormones in maintaining cognition in women, with evidence implicating menopause-related declines in 17β-estradiol in cognitive aging and AD risk. We will review research focused on the role of endogenous and exogenous estrogen exposure as a key underlying mechanism to neuropathological aging in women, with a focus on whether brain structure, function and neurochemistry respond to hormone treatment. While still in development, this research area offers a new sex-based perspective on brain aging and risk of AD, while also highlighting an urgent need for better integration between neurology, psychiatry, and women's health practices.

Sex Hormones, Sleep, and Memory: Interrelationships Across the Adult Female Lifespan

As the population of older adults grows, so will the prevalence of aging-related conditions, including memory impairments and sleep disturbances, both of which are more common among women. Compared to older men, older women are up to twice as likely to experience sleep disturbances and are at a higher risk of cognitive decline and Alzheimer's disease and related dementias (ADRD). These sex differences may be attributed in part to fluctuations in levels of female sex hormones (i.e., estrogen and progesterone) that occur across the adult female lifespan. Though women tend to experience the most significant sleep and memory problems during the peri-menopausal period, changes in memory and sleep have also been observed across the menstrual cycle and during pregnancy. Here, we review current knowledge on the interrelationships among female sex hormones, sleep, and memory across the female lifespan, propose possible mediating and moderating mechanisms linking these variables and describe implications for ADRD risk in later life.

The role of maternal exercise on placental, behavioral and genetic alterations induced by prenatal stress

The present study aimed to evaluate the effects of treadmill maternal exercise on alterations induced by prenatal stress in neonatal mice. Female and male Balb/c mice were divided into five groups: control (CON), prenatal restraint stress (PNS), prenatal restraint stress and physical exercise before pregnancy (PNS + EX1), prenatal restraint stress and physical exercise during pregnancy (PNS + EX2), and prenatal restraint stress and physical exercise before and during pregnancy (PNS + EX3). Exercise was performed using a treadmill, at a speed of 10 m/min, for 60 minutes, 5 days a week. Maternal behavior was assessed on days 3, 4 and 5 postpartum (PPD). Placental gene expression of glucocorticoid receptor (GR), 11-β-hydroxysteroid dehydrogenase 2 (11β-HSD2), 5-hydroxytryptamine receptor 1A (5HT_1AR), and corticotropin releasing hormone receptor 1 (CRHR1) were analyzed. In neonatal mice, the gene expression of GR, mineralocorticoid receptor (MR), CRHR1, 5HTr1, oxytocin Receptor 1 (OXTr1), tropomyosin related kinase B (TRκB), brain-derived neurotrophic factor exon I (BDNF I), and BDNF IV was analyzed in the brain (PND0) and hippocampus (PND10). Maternal exercise improved (p < 0.05) maternal care. In the placenta, maternal exercise prevented (p < 0.01) the increase in GR expression caused by PNS. In the brain from PND0, exercise before pregnancy prevented (p = 0.002) the decreased CRHR1 expression promoted by PNS. In the hippocampus of PND10 males, PNS decreased (p = 0.0005) GR expression, and exercise before pregnancy prevented (p = 0.003) this effect. In PND10 females, maternal exercise prevented (p < 0.05) the PNS-induced increase in MR expression. PNS + EX2 males showed increased (p < 0.01) BDNF I gene expression and PNS + EX1 females demonstrated increased (p = 0.03) BDNF IV expression. In conclusion, maternal physical exercise may play a role in modulating maternal-fetal health and may contribute to preventing neurodevelopmental changes induced by prenatal stress.

Endogenous and Exogenous Estrogen Exposures: How Women's Reproductive Health Can Drive Brain Aging and Inform Alzheimer's Prevention

After advanced age, female sex is the major risk factor for late-onset Alzheimer's disease (AD), the most common cause of dementia affecting over 24 million people worldwide. The prevalence of AD is higher in women than in men, with postmenopausal women accounting for over 60% of all those affected. While most research has focused on gender-combined risk, emerging data indicate sex and gender differences in AD pathophysiology, onset, and progression, which may help account for the higher prevalence in women. Notably, AD-related brain changes develop during a 10-20 year prodromal phase originating in midlife, thus proximate with the hormonal transitions of endocrine aging characteristic of the menopause transition in women. Preclinical evidence for neuroprotective effects of gonadal sex steroid hormones, especially 17β-estradiol, strongly argue for associations between female fertility, reproductive history, and AD risk. The level of gonadal hormones to which the female brain is exposed changes considerably across the lifespan, with relevance to AD risk. However, the neurobiological consequences of hormonal fluctuations, as well as that of hormone therapies, are yet to be fully understood. Epidemiological studies have yielded contrasting results of protective, deleterious and null effects of estrogen exposure on dementia risk. In contrast, brain imaging studies provide encouraging evidence for positive associations between greater cumulative lifetime estrogen exposure and lower AD risk in women, whereas estrogen deprivation is associated with negative consequences on brain structure, function, and biochemistry. Herein, we review the existing literature and evaluate the strength of observed associations between female-specific reproductive health factors and AD risk in women, with a focus on the role of endogenous and exogenous estrogen exposures as a key underlying mechanism. Chief among these variables are reproductive lifespan, menopause status, type of menopause (spontaneous vs. induced), number of pregnancies, and exposure to hormonal therapy, including hormonal contraceptives, hormonal therapy for menopause, and anti-estrogen treatment. As aging is the greatest risk factor for AD followed by female sex, understanding sex-specific biological pathways through which reproductive history modulates brain aging is crucial to inform preventative and therapeutic strategies for AD.

The Connection and Development of Unpredictability and Sensitivity in Maternal Care Across Early Childhood

Both patterns of maternal sensory signals and sensitive care have shown to be crucial elements shaping child development. However, research concerning these aspects of maternal care has focused mainly on maternal sensitivity with fewer studies evaluating the impact of patterns of maternal behaviors and changes in these indices across infancy and childhood. The aims of this study were to explore how maternal unpredictability of sensory signals and sensitivity develop and associate with each other from infancy to toddlerhood and whether elevated maternal depressive and anxiety symptoms relate to maternal unpredictable signals and sensitivity in toddlerhood. The study population consisted of 356 mother–child dyads assessed at 30 months; a subset of 103 mother–child dyads additionally participated in 8 months assessment. Maternal unpredictability and sensitivity were assessed from video-recorded free-play episodes at 8 and 30 months. Maternal depressive and anxiety symptoms were assessed with questionnaires at gestational weeks 14, 24, 34 and 3, 6, 12, and 24 months. Mean level of mothers’ unpredictability decreased on average whereas sensitivity did not change between infancy and toddlerhood. Both maternal unpredictability and sensitivity showed moderate level of individual stability from infancy to toddlerhood and these two measures were modestly correlated within each age. Elevated maternal depressive and anxiety symptoms were not related to unpredictability but related to lower maternal sensitivity in toddlerhood. These results identify unpredictable sensory signals as a characteristic of parental care that is independent of standard quality measures and suggest that it may be less influenced by maternal depressive and anxiety symptoms.

Influence of High Energy Diet and Polygenic Predisposition for Obesity on Postpartum Health in Rat Dams

It is estimated that 30% of pregnant women worldwide are overweight or obese, leading to adverse health effects for both mother and child. Women with obesity during pregnancy are at higher risk for developing both metabolic and mental disorders, such as diabetes and depression. Numerous studies have used rodent models of maternal obesity to understand its consequences on the offspring, yet characterization of changes in the dams is rare, and most rodent models rely solely on a high fat diet to induce maternal obesity, without regarding genetic propensity for obesity. Here we present the influence of both peripartum high energy diet (HE) and obesity-proneness on maternal health using selectively bred diet-resistant (DR) and diet-induced obese (DIO) rat dams. Outbred Sprague-Dawley rats were challenged with HE diet prior to mating and bred according to their propensity to gain weight. The original outbred breeding dams (F0) were maintained on low-fat chow during pregnancy and lactation. By comparison, the F1 dams consuming HE diet during pregnancy and lactation displayed higher gestational body weight gain (P < 0.01), and HE diet caused increased meal size and reduced meal frequency (P < 0.001). Sensitivity to the hormone amylin was preserved during pregnancy, regardless of diet. After several rounds of selective breeding, DIO and DR dams from generation F3 were provided chow or HE during pregnancy and lactation and assessed for their postpartum physiology and behaviors. We observed strong diet and phenotype effects on gestational weight gain, with DIO-HE dams gaining 119% more weight than DR-chow (P < 0.001). A high-resolution analysis of maternal behaviors did not detect main effects of diet or phenotype, but a subset of DIO dams showed delayed nursing behavior (P < 0.05). In generation F6/F7 dams, effects on gestational weight gain persisted (P < 0.01), and we observed a main effect of phenotype during a sucrose preference test (P < 0.05), with DIO-chow dams showing lower sucrose preference than DR controls (P < 0.05). Both DIO and DR dams consuming HE diet had hepatic steatosis (P < 0.001) and exhibited reduced leptin sensitivity in the arcuate nucleus (P < 0.001). These data demonstrate that both diet and genetic obesity-proneness have consequences on maternal health.

Long-term association of pregnancy and maternal brain structure: the Rotterdam Study

The peripartum period is the highest risk interval for the onset or exacerbation of psychiatric illness in women’s lives. Notably, pregnancy and childbirth have been associated with short-term structural and functional changes in the maternal human brain. Yet the long-term effects of pregnancy on maternal brain structure remain unknown. We investigated a large population-based cohort to examine the association between parity and brain structure. In total, 2,835 women (mean age 65.2 years; all free from dementia, stroke, and cortical brain infarcts) from the Rotterdam Study underwent magnetic resonance imaging (1.5 T) between 2005 and 2015. Associations of parity with global and lobar brain tissue volumes, white matter microstructure, and markers of vascular brain disease were examined using regression models. We found that parity was associated with a larger global gray matter volume (β = 0.14, 95% CI = 0.09–0.19), a finding that persisted following adjustment for sociodemographic factors. A non-significant dose-dependent relationship was observed between a higher number of childbirths and larger gray matter volume. The gray matter volume association with parity was globally proportional across lobes. No associations were found regarding white matter volume or integrity, nor with markers of cerebral small vessel disease. The current findings suggest that pregnancy and childbirth are associated with robust long-term changes in brain structure involving a larger global gray matter volume that persists for decades. Future studies are warranted to further investigate the mechanism and physiological relevance of these differences in brain morphology.

Evidence for cognitive plasticity during pregnancy via enhanced learning and memory

Human and animal neuroscience studies support the view that plastic shifts occur in the brain during pregnancy that support the emergence of new maternal behaviours. The idea of adaptive plasticity in pregnancy is at odds with the notion of "baby brain", in which pregnant women describe the onset of forgetfulness. While inconsistent evidence for memory deficits during pregnancy has been reported, few studies have investigated spatial associative memory (which is consistently enhanced in studies of pregnant rodents). Moreover, most studies assess domain-general stimuli, which might miss adaptations specific to parent-relevant stimuli. In the present study, we examined the retention of spatial associative memory for parenting-relevant and non-parenting-relevant stimuli across 4-weeks in a sample of women in their third trimester of pregnancy, and compared their performance to a sample of never pregnant women. We demonstrated that relative to never pregnant women, pregnant women exhibited enhanced long-term retention of object-scene-location associations (spatial associative memory), as well as better initial learning about parenting-relevant, relative to non-parenting-relevant, stimuli. Thus, similar to studies in rodents, cognitive improvements were seen during pregnancy in humans, and those improvements were specific to the domain of spatial associative retention, and in the recognition of stimuli relevant to parenting.

Association of Reproductive History With Brain MRI Biomarkers of Dementia Risk in Midlife

BACKGROUND AND OBJECTIVES

To examine associations between indicators of estrogen exposure from women's reproductive history and brain MRI biomarkers of Alzheimer disease (AD) in midlife.

METHODS

We evaluated 99 cognitively normal women 52 ± 6 years of age and 29 men 52 ± 7 years of age with reproductive history data, neuropsychological testing, and volumetric MRI scans. We used multiple regressions to examine associations among reproductive history indicators, voxel-wise gray matter volume (GMV), and memory and global cognition scores, adjusting for demographics and midlife health indicators. Exposure variables were menopause status, age at menarche, age at menopause, reproductive span, hysterectomy status, number of children and pregnancies, and use of menopause hormonal therapy (HT) and hormonal contraceptives (HC).

RESULTS

All menopausal groups exhibited lower GMV in AD-vulnerable regions compared to men, with perimenopausal and postmenopausal groups also exhibiting lower GMV in temporal cortex compared to the premenopausal group. Reproductive span, number of children and pregnancies, and use of HT and HC were positively associated with GMV, chiefly in temporal cortex, frontal cortex, and precuneus, independent of age, APOE ε4 status, and midlife health indicators. Although reproductive history indicators were not directly associated with cognitive measures, GMV in temporal regions was positively associated with memory and global cognition scores.

DISCUSSION

Reproductive history events signaling more estrogen exposure such as premenopausal status, longer reproductive span, higher number of children, and use of HT and HC were associated with larger GMV in women in midlife. Further studies are needed to elucidate sex-specific biological pathways through which reproductive history influences cognitive aging and AD risk.