Measuring stress responses in postpartum mothers: perspectives from studies in human and animal populations

Association between breastfeeding and new mothers' sleep: a unique Australian time use study

BACKGROUND

Infant sleep is of great interest to new parents. There is ongoing debate about whether infants fed with breastmilk substitutes sleep longer than those exclusively or partially breastfed, but what does this mean for the mother? What expectations are realistic for mothers desiring to exclusively breastfeed as recommended by health authorities? There are both biological and social influences on infant and maternal sleep. More accurate information on average maternal sleep hours for diverse feeding practices may help guide realistic expectations and better outcomes for mothers, infants and families.

METHODS

Using a unique time use dataset purposefully designed to study the time use of new mothers, this study investigated whether the weekly duration of maternal sleep, sleep disturbance, unpaid housework, and free time activities differed by detailed feeding method. The study collected 24/7 time use data from 156 mothers of infants aged 3, 6 and/or 9 months between April 2005 and April 2006, recruited via mother's groups, infant health clinics, and childcare services throughout Australia. Sociodemographic and feeding status data were collected by questionnaire. Statistical analysis used linear mixed modelling and residual maximum likelihood analysis to compare effects of different infant feeding practices on maternal time use.

RESULTS

There were no significant differences in time spent asleep between lactating and non lactating mothers, though lactating mothers had more time awake at night. Lactating mothers spent more time (8.5 h weekly) in childcaring activity (p = 0.007), and in employment (2.7 vs. 1.2 h, p < 0.01), but there were no significant differences in free time. Those not breastfeeding spent more time in unpaid domestic work. Exclusive breastfeeding was associated with reduced maternal sleep hours (average 7.08 h daily). Again, free time did not differ significantly between feeding groups. Exclusively breastfeeding mothers experienced reduced sleep hours, but maintained comparable leisure time to other mothers by allocating their time differently. Domestic work hours differed, interacting in complex ways with infant age and feeding practice.

CONCLUSIONS

Optimal breastfeeding may require realistic maternal sleep expectations and equitable sharing of paid and unpaid work burdens with other household members in the months after the birth of an infant.

Socio-Ecological Challenges as Modulators of Women's Reproductive Trajectories

Amenorrhea, anovulatory cycles, miscarriages, and other reproductive outcomes are often seen as pathological. Life history theory, in contrast, treats those outcomes as adaptations that helped women optimize the timing of reproductive ventures across our evolutionary history. Women's bodies adjust their reproductive strategies in response to socio-ecological conditions, a process mediated by the hypothalamic-pituitary-adrenal axis (HPAA). Here, we review the links between socio-ecological conditions, HPAA activity, and the pace of women's reproductive transitions such as puberty, age at first birth, interbirth interval, and perimenopause. We also discuss the HPAA's role as a modulator of reproductive function: It not only suppresses it but may also prime women's bodies for future reproductive ventures. We conclude by reviewing challenges and opportunities within our subfield, including the need for transdisciplinary teams to develop longitudinal studies to improve our understanding of women's reproductive trajectories and outcomes from the moment they are conceived.

Correlates of maternal glucocorticoid levels in a socially flexible rodent

While it is generally accepted that social isolation has detrimental effects on social species, little is known about the importance of social interactions in less social species-particularly for wild reproductive females. We studied socially-flexible yellow-bellied marmots (Marmota flaviventer) and asked whether features of the social environment are associated with maternal fecal glucocorticoid metabolite (FGM) concentrations. Since changes in maternal baseline glucocorticoids may have positive or negative consequences for offspring fitness, we were also interested in estimating their relationship with measures of reproductive success. We fitted generalized linear mixed effects models to a dataset including maternal FGM measurements, social network metrics, maternal/alloparental care, and pup FGM and survival. Agonistic interactions were positively associated with maternal FGM levels, while mothers that engaged in relatively more affiliative interactions had reduced FGM levels when living in environments with low predator pressure. Pups associated with mothers exhibiting high FGM levels had low annual survival rates, received less maternal/alloparental care and had higher FGM levels. Interestingly, offspring from mothers with high FGM levels were more likely to survive the summer when born in small litters. In sum, social interactions likely influence and are influenced by glucocorticoid levels of facultatively social females. Potential benefits of social bonds may be context-specific, and agonistic interactions may be tightly correlated with fitness. Female marmots exhibiting high FGM levels had overall low reproductive success, which is predicted by the cort-fitness hypothesis. However, under adverse conditions, offspring summer survival can be maximized if pups are born in small litters.

Experience of Adversity during a First Lactation Modifies Prefrontal Cortex Morphology in Primiparous Female Rats: Lack of Long Term Effects on a Subsequent Lactation

Reproductive experience is associated with morphological and functional plasticity in brain areas important for cognitive and emotional responses, including the infralimbic (IL) medial prefrontal cortex (mPFC). Here we examined whether suboptimal conditions during a first lactation could modify lactation-induced morphological IL mPFC changes, leading to alterations in stress responses and attention and whether any observed effects would persist into a second lactation. Reduced availability of bedding and nesting material (LB) was used to induce unfavorable conditions in primiparous (P) mothers. In normal bedding (NB) conditions, P mothers exhibited high spine number and density on postpartum day (PPD)10, which greatly decreased 2 weeks after weaning of their pups. In contrast, P-LB mothers had a lower spine number and density on PPD10, which markedly increased after weaning. LB exposure did not modify stress responsiveness to a ferret odor on PPD5 in primiparous or in multiparous (M) females. Number of errors and trials to criterion in the attention set shifting task were not modified by a history of adversity in multiparous females, although this group tended to exhibit higher attentional abilities than M-NB females. These results suggest that adversity acutely reduces morphological plasticity in the maternal mPFC during lactation, an effect that is not associated with significant changes in stress responses and/or glucocorticoid production. Medial PFC morphological changes induced by LB subside during a subsequent lactation as does the effect of maternity itself.

Effects of single parenthood on mothers' behavior, morphology, and endocrine function in the biparental California mouse

Motherhood is energetically costly for mammals and is associated with pronounced changes in mothers' physiology, morphology and behavior. In ~5% of mammals, fathers assist their mates with rearing offspring and can enhance offspring survival and development. Although these beneficial consequences of paternal care can be mediated by direct effects on offspring, they might also be mediated indirectly, through beneficial effects on mothers. We tested the hypothesis that fathers in the monogamous, biparental California mouse (Peromyscus californicus) reduce the burden of parental care on their mates, and therefore, that females rearing offspring with and without assistance from their mates will show differences in endocrinology, morphology and behavior, as well as in the survival and development of their pups. We found that pups' survival and development in the lab did not differ between those raised by a single mother and those reared by both mother and father. Single mothers spent more time in feeding behaviors than paired mothers. Both single and paired mothers had higher lean mass and/or lower fat mass and showed more anxiety-like behavior in open-field tests and tail-suspension tests, compared to non-breeding females. Single mothers had higher body-mass-corrected liver and heart masses, but lower ovarian and uterine masses, than paired mothers and/or non-breeding females. Mass of the gastrointestinal tract did not differ between single and paired mothers, but single mothers had heavier gastrointestinal tract compared to non-breeding females. Single motherhood also induced a flattened diel corticosterone rhythm and a blunted corticosterone response to stress, compared to non-breeding conditions. These findings suggest that the absence of a mate induces morphological and endocrine changes in mothers, which might result from increased energetic demands of pup care and could potentially help maintain normal survival and development of pups.

Perceived Psychological Traumatic Childbirth in Iranian Mothers: Diagnostic Value of Coping Strategies

Objectives

The aim of this study was to investigate the diagnostic value of a stress coping scale for predicting perceived psychological traumatic childbirth in mothers.

Methods

This cross-sectional study was performed on 400 new mothers (within 48 hours of childbirth). Psychological traumatic childbirth was evaluated using the 4 diagnostic criteria of Diagnostic and Statistical Manual of Mental Disorders. Coping was measured using Moss and Billings' Stress Coping Strategies Scale.

Results

The overall mean score of stress coping was 29 ± 14.2. There were 193 (43.8%) mothers that had experienced a psychological traumatic childbirth. A stress coping score ≤ 30, with a sensitivity of 90.16 (95% CI = 85.1-94.0), and a specificity of 87.44 (95% CI = 82.1-91.6), was determined as a predictor of psychological traumatic childbirth. So that among mothers with stress coping scores ≤ 30, 87% had experienced a psychological traumatic childbirth.

Conclusion

Investigating the degree of coping with stress can be used as an accurate diagnostic tool for psychological traumatic childbirth. It is recommended that during pregnancy, problem-solving and stress management training programs be used as psychological interventions for mothers with low levels of stress control. This will ensure that they can better cope with traumatic childbirth and post-traumatic stress in the postpartum stage.

The long and short term effects of motherhood on the brain

Becoming a mother is associated with dramatic changes in physiology, endocrinology, immune function, and behaviour that begins during pregnancy and persists into the postpartum. Evidence also suggests that motherhood is accompanied by long-term changes in brain function. In this review, we summarize the short (pregnancy and postpartum) and long-term (beyond the postpartum and into middle age) effects of pregnancy and motherhood on cognition, neuroplasticity, and neuroimmune signalling. We also discuss the effects of previous history of pregnancy and motherhood (parity) on brain health and disease (neurodegenerative diseases and stroke outcomes) and on efficacy of hormone and antidepressant treatments. Finally, we argue that pregnancy and motherhood are unique female experiences that need to be taken into account to better understand female brain function and aging.

Gating of the neuroendocrine stress responses by stressor salience in early lactating female rats is independent of infralimbic cortex activation and plasticity

In early lactation (EL), stressor salience modulates neuroendocrine stress responses, but it is unclear whether this persists throughout lactation and which neural structures are implicated. We hypothesized that this process is specific to EL and that the infralimbic (IL) medial prefrontal cortex (mPFC) might provide a critical link between assessment of threat and activation of the hypothalamo-pituitary-adrenal (HPA) axis in EL. We measured neuroendocrine responses and neuronal Fos induction to a salient (predator odor) or non-salient (tail pinch) psychogenic stressor in EL and late lactation (LL) females. We found that EL females exhibited a large response to predator stress only in the presence of pups, while responses to tail pinch were reduced independently of pup presence. In LL, HPA axis responses were independent of pup presence for both stressors and only responses to tail pinch were modestly reduced compared to virgins. Intracerebral injection of the local anesthetic bupivacaine (BUP) (0.75%; 0.5 µl/side) in the IL mPFC did not differentially affect neuroendocrine responses to predator odor in virgin and EL females, suggesting that lactation-induced changes in this structure might not regulate stressor salience for the HPA axis. However, the IL mPFC displayed morphological changes in lactation, with significant increases in dendritic spine numbers and density in EL compared to LL and virgin females. EL females also showed improved performance in the attention set-shifting task (AST), which could reflect early plasticity in the IL mPFC at a time when rapid adaptation of the maternal brain is necessary for pup survival.

The effectiveness of interventions using relaxation therapy to improve breastfeeding outcomes: A systematic review

Maternal psychological state is recognised to influence lactation success, largely by affecting milk ejection. Thus, increased psychological distress can disrupt milk flow and in the long‐term, affect milk synthesis. Conversely, it is possible that milk ejection could be improved by using relaxation therapy during breastfeeding. We performed a systematic review to evaluate the effectiveness of interventions using relaxation therapy to improve breastfeeding outcomes and to assess the consequent impact(s) on infant growth and behaviour. A literature search was performed using the PRISMA guidelines where we included intervention studies (including nonrandomised controlled studies) using relaxation therapy in breastfeeding mothers during the post‐natal period. Out of 147 identified records at the initial search, 5 studies were eligible, of which 3 were randomised controlled trials and 2 were nonrandomised or quasi‐experimental studies. These studies were conducted in Europe, America, and India and included 311 mother–infant pairs, of which 64 infants were full‐term and 247 were premature infants. Relaxation therapy was shown to increase milk yield in mothers of preterm infants in 2 randomised trials, however, the milk sampling protocol for these studies could be questioned. None of the studies investigated the consequent effects on infant outcomes. Overall, limited evidence was found on the effectiveness of relaxation therapy on breast milk composition and infant outcomes. Experimental studies with better standardisation of protocol and robust methodological design are needed to investigate the effectiveness of relaxation therapy on both breastfeeding and infant growth and behavioural outcomes.

Maternal Time Use and Nurturing: Analysis of the Association Between Breastfeeding Practice and Time Spent Interacting with Baby

BACKGROUND

Breastfeeding supports child development through complex mechanisms that are not well understood. Numerous studies have compared how well breastfeeding and nonbreastfeeding mothers interact with their child, but few examine how much interaction occurs.

SUBJECTS AND METHODS

Our study of weekly time use among 156 mothers of infants aged 3-9 months investigated whether lactating mothers spend more time providing emotional support or cognitive stimulation of their infants than nonbreastfeeding mothers, and whether the amount of such interactive time is associated with breastfeeding intensity. Mothers were recruited via mother's and baby groups, infant health clinics, and childcare services, and used an electronic device to record their 24-hour time use for 7 days. Sociodemographic and feeding status data were collected by questionnaire. Statistical analysis using linear mixed modeling and residual maximum likelihood analysis compared maternal time use for those giving "some breastfeeding" and those "not breastfeeding." Analysis was also conducted for more detailed feeding subgroups.

RESULTS

Breastfeeding and nonbreastfeeding mothers had broadly similar socioeconomic and demographic characteristics. Breastfeeding was found to be associated with more mother-child interaction time, a difference only partially explained by weekly maternal employment hours or other interactive care activities such as play or reading.

CONCLUSION

This study presents data suggesting that lactating mothers spent significantly more hours weekly on milk feeding and on carrying, holding, or soothing their infant than nonlactating mothers; and on providing childcare. Understanding the mechanisms by which child mental health and development benefits from breastfeeding may have important implications for policies and intervention strategies, and could be usefully informed by suitably designed time use studies.

Postpartum Anxiety and Infant-Feeding Outcomes

There is increasing evidence for the effect of postpartum anxiety (PPA) on maternal and infant health outcomes. Despite evidence linking suboptimal infant-feeding outcomes with other indices of maternal mental health, the relationship between PPA and infant feeding has not yet been reviewed. A systematic review with narrative synthesis was conducted to examine the relationship between PPA and infant-feeding outcomes. Electronic searches were performed using specific keywords (eg, "postnatal anxiet*"; "breastfeed*"). A hand search of selected journals and reference lists of included articles was then conducted. All studies were considered that provided information related to PPA and infant-feeding outcomes. One hundred and two studies were identified, of which 33 were eligible. Two authors independently extracted data including study design, participants, and results. Results indicated that women with symptoms of PPA are less likely to breastfeed exclusively and more likely to terminate breastfeeding earlier. Some evidence also suggests that those experiencing PPA are less likely to initiate breastfeeding and more likely to supplement with formula in the hospital. In those who do breastfeed, PPA reduces self-efficacy, increases breastfeeding difficulties, and may negatively affect breastfeeding behaviors and breast milk composition. Heterogeneous outcomes and methodological limitations somewhat limit the comparability of findings. However, in combination with a review linking depression with similar negative infant-feeding sequelae, the findings provide evidence for the effect of negative postpartum mood on breastfeeding. Additional support for breastfeeding mothers with PPA is warranted.

Cortisol response to the Trier Social Stress Test in pregnant women at risk for postpartum depression

Antepartum depression and anxiety are risk factors for postpartum depression (PPD). Postpartum abnormalities in hypothalamic-pituitary-adrenal (HPA) reactivity are associated with PPD. It is not known if antepartum HPA abnormalities exist in women at risk for PPD (AR-PPD). We measured salivary cortisol response to the Trier Social Stress Test (TSST) in 44 (24 AR-PPD, 20 healthy comparison) pregnant women. Depression and anxiety were measured using the Edinburgh Postnatal Depression Scale (EPDS) and Spielberger State-Trait Anxiety Inventory-State (STAI-S). We analyzed longitudinal changes in cortisol using generalized estimating equation methods to control for the correlation within subjects at the six TSST time points. Group differences in area under the curve (AUC) were examined. A majority (70.8 %) of the AR-PPD had prior depression. EPDS total score was higher in AR-PPD vs. comparison women (mean EPDS = 9.8 ± 4.9 vs. mean EPDS = 2.4 ± 2.0 respectively, p < 0.001). Mean STAI-S total score was higher in AR-PPD vs. comparison women at all TSST time points and over time (z = 2.71, df = 1, p = 0.007). There was no significant difference in cortisol concentration over time between groups. We observed no detectable difference in cortisol response to psychosocial stress induced by the TSST despite clinically significant between-group differences in current/past depression and current symptomatology.

Gestational hormone profiles predict human maternal behavior at 1-year postpartum

In many non-human species, including primates, gestational reproductive hormones play an essential role in the onset of maternal motivation and behaviors. We investigated the associations between prepartum estradiol and progesterone and maternal behavior at 1-year postpartum in 177 women. Blood was obtained at five gestational time points and an index of quality of maternal care was determined using a well-validated mother-child interaction protocol. Women who exhibited higher quality maternal care at 1-year postpartum were characterized by unique gestational profiles of estradiol, progesterone and the estrogen to progesterone ratio; specifically by slower accelerations and levels of these hormone trajectories beginning in midgestation. Further, it appeared that both fetal sex and parity moderated these findings, with first time mothers and mothers of females showing stronger associations. In sum, these data document persisting associations between prepartum hormone profiles and human maternal behavior. More broadly, these findings add to the growing literature highlighting the perinatal period as one of critical neurodevelopment in the lifespan of the human female.

Peromyscus as a model system for understanding the regulation of maternal behavior

The genus Peromyscus has been used as a model system for understanding maternal behavior because of the diversity of reproductive strategies within this genus. This review will describe the ecological factors that determine litter size and litter quality in polygynous species such as Peromyscus leucopus and Peromyscus maniculatus. We will also outline the physiological and social factors regulating maternal care in Peromyscus californicus, a monogamous and biparental species. Because biparental care is relatively rare in mammals, most research in P. californicus has focused on understanding the biology of paternal care while less research has focused on understanding maternal care. As a result, the social, sensory, and hormonal cues used to coordinate parental care between male and female P. californicus have been relatively well-studied. However, less is known about the physiology of maternal care in P. californicus and in other Peromyscus species. The diversity of the genus Peromyscus provides the potential for future research to continue to examine how variation in social systems has shaped the mechanisms that underlie maternal care.

Stress, cortisol, and obesity: a role for cortisol responsiveness in identifying individuals prone to obesity

There is a strong inter-relationship between activation of the hypothalamo-pituitary-adrenal axis and energy homeostasis. Patients with abdominal obesity have elevated cortisol levels. Furthermore, stress and glucocorticoids act to control both food intake and energy expenditure. In particular, glucocorticoids are known to increase the consumption of foods enriched in fat and sugar. It is well-known that, in all species, the cortisol response to stress or adrenocorticotropin is highly variable. It has now emerged that cortisol responsiveness is an important determinant in the metabolic sequelae to stress. Sheep that are characterized as high-cortisol responders (HRs) have greater propensity to weight gain and obesity than low-cortisol responders (LRs). This difference in susceptibility to become obese is associated with a distinct metabolic, neuroendocrine, and behavioral phenotype. In women and ewes, HR individuals eat more in response to stress than LR. Furthermore, HR sheep have impaired melanocortin signaling and reduced skeletal muscle thermogenesis. High-cortisol responder sheep exhibit reactive coping strategies, whereas LRs exhibit proactive coping strategies. This complex set of traits leads to increased food intake and reduced energy expenditure in HR and thus, predisposition to obesity. We predict that cortisol responsiveness may be used as a marker to identify individuals who are at risk of weight gain and subsequent obesity.

Breastfeeding, Bed-Sharing, and Maternal Cortisol

Prior studies have found that close mother-child sleep proximity helps increase rates of breastfeeding, and breastfeeding itself is linked to better maternal and infant health. In this study, we examine whether breastfeeding and infant bed-sharing are related to daily rhythms of the stress-responsive hormone cortisol. We found that bed-sharing was related to flatter diurnal cortisol slopes, and there was a marginal effect for breastfeeding to predict steeper cortisol slopes. Furthermore, mothers who breastfeed but do not bed-share had the steepest diurnal cortisol slopes, whereas mothers who bed-shared and did not breastfeed had the flattest slopes (P < .05). These results were significant after controlling for subjective sleep quality, perceived stress, depression, socioeconomic status, race, and maternal age. Findings from this study indicate that infant parenting choices recommended for infants (breastfeeding and separate sleep surfaces for babies) may also be associated with more optimal stress hormone profiles for mothers.

Measuring stress responses in female Geoffroy's spider monkeys: Validation and the influence of reproductive state

Fecal glucocorticoid metabolites are increasingly used to investigate physiological stress. However, it is crucial for researchers to simultaneously investigate the effects of reproductive state because estradiol and placental hormones can affect circulating glucocorticoid concentrations. Reports on the relationships between glucocorticoids and reproductive state are inconsistent among females. Unlike several primate species that have heightened glucocorticoid activity during lactation, humans experience reduced glucocorticoid activity during lactation. Rather than a taxonomic difference, we hypothesize that this is a result of different environmental stressors, particularly the threat of infanticide. Here, we expand the number of wild primate species tested by validating a glucocorticoid assay for female Geoffroy's spider monkeys. We investigate the effects of reproductive state on their glucocorticoid concentrations. Utilizing a routine veterinary exam on a captive population, we determined that fecal glucocorticoid metabolites increase in response to a stressor (anesthesia), and this rise is detected approximately 24 hr later. Additionally, we found that extracted hormone patterns in a wild population reflected basic reproductive biology-estradiol concentrations were higher in cycling than lactating females, and in lactating females with older offspring who were presumably resuming their cycle. However, we found that estradiol and glucocorticoid concentrations were significantly correlated in lactating but not cycling females. Similarly, we found that reproductive state and estradiol concentration, but not stage of lactation, predicted glucocorticoid concentrations. Unlike patterns in several other primate species that face a relatively strong threat of infanticide, lactating spider monkeys experience reduced glucocorticoid activity, possibly due to attenuating effects of oxytocin and lower male-initiated aggression than directed at cycling females. More broadly, we conclude that future studies using fecal glucocorticoid metabolites to index stress should consider that reproductive state might confound glucocorticoid measurements. Am. J. Primatol. 77:925-935, 2015. © 2015 Wiley Periodicals, Inc.

Correlation between maternal and infant cortisol varies by breastfeeding status

OBJECTIVE

The objective of this study was to examine associations of mother and infant salivary cortisol, measured three times over the course of a day, and assess whether these varied by breastfeeding status.

METHODS

We conducted a cross-sectional study of 54 mothers and their infants aged 4-11 months. Mothers collected their own saliva and that of their infants upon awakening, 30min after waking and at bedtime. Breastfeeding status was reported by mothers and cortisol level was measured in saliva in μg/dl using standard techniques. We used generalized linear models to evaluate relationships between maternal and infant cortisol levels, and assessed whether the relationship differed by breastfeeding status: formula only compared to partial and full breastfeeding, adjusting for infant sex, race, age, maternal education, and family income.

RESULTS

Thirty-four infants received formula only and 20 were either partially or fully breastfed. Breastfeeding was associated with higher household income, higher maternal education, and white race. Cortisol levels were higher among breastfed infants at all three time points. After adjustment, maternal cortisol levels were related with infant cortisol at bedtime only (regression estimate 0.06; 95% CI: 0.10, 1.1; p=0.02). The adjusted association between bedtime maternal and infant cortisol was stronger among breastfeeding dyads than among formula-feeding dyads (regression estimate 1.0; 95% CI: 0.1, 2.0; p=0.04 vs. 0.6; CI: -0.1, 1.3; p=0.10). In addition, we assessed the influence of maternal education and household income in our adjusted model; income strengthened the observed association, whereas maternal education did not change the estimate.

CONCLUSIONS

Breastfeeding mothers and infants had significant correlations for cortisol at bedtime, while formula-feeding dyads did not. These data suggest that several factors may contribute to cortisol synchrony observed in mother/infant dyads, including the transfer of cortisol in human milk, physical interaction such as skin-to-skin contact, and shared environment. In addition, our findings support household income as a possible contributor.

Influence of transrectal and transabdominal ultrasound examination on salivary cortisol, heart rate, and heart rate variability in mares

Pregnancy diagnostics in equine reproduction are routinely performed using transrectal ultrasonography, although it is also possible to visualize the fetus by transabdominal ultrasound examinations from the 90th day of gestation onward. We hypothesized that ultrasound examinations may stress the mare and that the gestational stage status and lactation may influence the mare's stress reaction. To investigate the stress reaction, 25 thoroughbred mares of different age, pregnancy and lactational status underwent a transrectal examination. In pregnant mares, an additional transabdominal examination was performed. Salivary cortisol concentration, mean heart rate, and heart rate variability of mares were assessed to evaluate the reactions of hypothalamic-pituitary-adrenal (HPA) axis and of the autonomic nervous system. Significant differences were observed between lactating and nonlactating mares; with a lower responsiveness to stress in lactating mares. The transrectal ultrasound examination in nonlactating mares induced a significant increase in salivary cortisol (P < 0.05), and in the heart rate variability parameter, ratio of low to high frequencies (P < 0.05). This reflects an activation of the HPA axis and a shift to more sympathetic dominance. In contrast, a transabdominally performed pregnancy check did not induce an activation of the HPA axis over basal level but increased the mean heart rate and low to high frequency ratio. The results of this study indicate that checks of advanced pregnancies can be easily performed by transabdominal ultrasonography. With regard to animal welfare, this technique should be preferred during midgestation in nonlactating mares.

Maternal anxiety and breastfeeding: findings from the MAVAN (Maternal Adversity, Vulnerability and Neurodevelopment) Study

BACKGROUND

Maternal anxiety and depression may impair maternal intention, motivation, and self-efficacy in multiple domains associated with child health including breastfeeding.

OBJECTIVE

We tested the hypothesis that mothers who experience substantial anxiety during pregnancy or the postpartum period are at increased risk for reduced initiation, exclusivity, and continuation of breastfeeding.

METHODS

We obtained data on 255 Canadian pregnant women from the Maternal Adversity, Vulnerability and Neurodevelopment (MAVAN) study recruited between June 2004 and February 2009. We utilized data collected from 18 to 23 weeks gestation through 12 months postpartum. Multivariate logistic regression was used to assess whether scores on the Hamilton Anxiety Scale (HAM-A) and State-Trait Anxiety Inventory (STAI) were associated with initiation, exclusivity, and continuation of breastfeeding.

RESULTS

Prenatal anxiety was not associated with breastfeeding outcomes. In adjusted models, a single point increase in HAM-A scores at 3 months postpartum was associated with an 11% reduction in the odds of exclusive breastfeeding at 6 months (adjusted odds ratio [aOR] = 0.89; 95% CI, 0.80-0.99). A single point increase in STAI State and STAI Trait scores at 3 months postpartum was associated with a 4% (aOR = 0.96; 95% CI, 0.92-0.99) and 7% (aOR = 0.93; 95% CI, 0.86-1.00) reduction, respectively, in the odds of any breastfeeding at 12 months.

CONCLUSION

Our findings suggest a relationship between maternal anxiety and reduced exclusivity and continuation of breastfeeding. Maternal anxiety should be actively monitored and managed appropriately in the postpartum period to support optimal breastfeeding practices.

Oxytocin and Epstein-Barr virus: Stress biomarkers in the postpartum period among first-time mothers from São Paulo, Brazil

OBJECTIVES

The purpose of the study was to examine the relationship between self-reported stress levels among new mothers in São Paulo, Brazil and two biomarkers of stressful experience, oxytocin (OT) and Epstein-Barr Virus antibody level (EBV-ab), with planned pregnancy hypothesized as a moderator of biological response to stressful conditions.

METHODS

Sixty-three first-time mothers between the ages of 15 and 45 were recruited from neighborhoods in São Paulo, Brazil. Quantitative and qualitative data were collected longitudinally, bi-weekly between two and 12 weeks postpartum. OT level was assessed from breast milk samples and EBV-ab from blood spot samples. An Interpersonal Satisfaction scale was developed, validated, and administered, along with the Cohen perceived stress scale (PSS).

RESULTS

In-depth interview data revealed unplanned pregnancy to be a significant stressor in the lives of first-time mothers. In linear regression, OT level was negatively associated with interpersonal satisfaction score (P = 0.022) and positively associated with PSS score (P = 0.007). When splitting the sample by planned status of the pregnancy, women with an unplanned pregnancy showed a strengthened positive association between OT level and PSS (P = 0.001; Adj R(2) = 0.44) and negative association with interpersonal satisfaction (P = 0.017; Adj R(2) = 0.15), while no associations existed for women with a planned pregnancy. EBV-ab level was not correlated or associated with stress/satisfaction measures.

CONCLUSION

OT is an effective biomarker in the measurement of stress in the body, and additionally reflects differential experiences with difficult interpersonal circumstances, such as unplanned pregnancy. By contrast, EBV-ab failed to reflect differences in self-reported stress levels between mothers.

Flexibility and adaptation of the neural substrate that supports maternal behavior in mammals

Maternal behavior is species-specific and expressed under different physiological conditions, and contexts. It is the result of neural processes that support different forms (e.g. postpartum, cycling sensitized and spontaneous maternal behavior) and modalities of mother-offspring interaction (e.g. maternal interaction with altricial/precocious young; selective/non-selective bond). To understand how the brain adapts to and regulates maternal behavior in different species, and physiological and social conditions we propose new neural models to explain different forms of maternal expression (e.g. sensitized and spontaneous maternal behavior) and the behavioral changes that occur across the postpartum period. We emphasize the changing role of the medial preoptic area in the neural circuitry that supports maternal behavior and the cortical regulation and adjustment of ongoing behavioral performance. Finally, we discuss how our accumulated knowledge about the psychobiology of mothering in animal models supports the validity of animal studies to guide our understanding of human mothering and to improve human welfare and health.

Effect of reproductive status on hypothalamic-pituitary-adrenal (HPA) activity and reactivity in male California mice (Peromyscus californicus)

Previous studies indicate that reproductive condition can alter stress response and glucocorticoid release. Although the functional significance of hypothalamic-pituitary-adrenal (HPA) axis modulation by breeding condition is not fully understood, one possible explanation is the behavior hypothesis, which states that an animal's need to express parental behavior may be driving modulation of the HPA axis. This possibility is consistent with findings of blunted activity and reactivity of the HPA axis in lactating female mammals; however, effects of reproductive status on HPA function have not been well characterized in male mammals that express parental behavior. Therefore, we tested this hypothesis in the monogamous and biparental California mouse. Several aspects of HPA activity were compared in males from three reproductive conditions: virgin males (housed with another male), non-breeding males (housed with a tubally ligated female), and first-time fathers (housed with a female and their first litter of pups). In light of the behavior hypothesis we predicted that new fathers would differ from virgin and non-breeding males in several aspects of HPA function and corticosterone (CORT) output: decreased amplitude of the diurnal rhythm in CORT, a blunted CORT increase following predator-odor stress, increased sensitivity to glucocorticoid negative feedback, and/or a blunted CORT response to pharmacological stimulation. In addition, we predicted that first-time fathers would be more resistant to CORT-induced suppression of testosterone secretion, as testosterone is important for paternal behavior in this species. We found that virgin males, non-breeding males and first-time fathers did not display any CORT differences in diurnal rhythm, response to a predator-odor stressor, or response to pharmacological suppression or stimulation. Additionally, there were no differences in circulating testosterone concentrations. Adrenal mass was, however, significantly lower in new fathers than in virgin or non-breeding males. These results suggest that the behavior hypothesis does not explain HPA function across reproductive conditions in male California mice.

Adaptive changes in basal and stress-induced HPA activity in lactating and post-lactating female rats

Lactation represents a period of marked adaptation of the hypothalamo-pituitary-adrenal HPA axis. We characterized basal and stress-induced HPA activity during lactation and experimental weaning using dynamic blood sampling in rats. Pulsatile and diurnal corticosterone release occurred at all reproductive stages studied (virgin; day 10 of lactation; 3 and 14 days after experimental weaning on day 10 of lactation). However, in lactating rats the diurnal peak was significantly reduced, resulting in a flattened rhythm, and three days after weaning, basal HPA activity was markedly suppressed: the number of pulses and underlying basal levels of corticosterone were reduced and the diurnal rise phase delayed. Marked changes in the HPA response to 10 min noise stress also occurred at these times: being completely absent in lactating animals, but restored and highly prolonged in early weaned animals. Injection of methylprednisolone (2 mg, iv) was used to determine whether changes in fast glucocorticoid suppression correlated with these adaptive changes. Methylprednisolone induced a rapid suppression of corticosterone in virgin animals, but this effect was markedly attenuated in lactating and early weaned animals and was accompanied by significant changes in relative expression of hippocampal glucocorticoid and mineralocorticoid receptor mRNA. All effects were reversed or partially reversed 14 days after experimental weaning. Thus, the presence of the pups has an important influence on regulation of the HPA axis, and while postpartum adaptations are reversible, acute weaning evokes marked reorganisation of basal and stress-induced HPA activity.

Maternal behaviour and peripartum levels of oestradiol and progesterone show little difference in Merino ewes selected for calm or nervous temperament under indoor housing conditions

Temperament influences the expression of maternal behaviour in sheep under experimental field conditions. We investigated whether maternal behaviour between ewes selected for a calm or nervous temperament is independent from environmental conditions. In addition, the level of maternal behaviour expressed by mothers is correlated with the concentration of hormones during the peripartum period. Therefore, we investigated whether the selection for temperament had resulted in hormonal differences between the two lines with regard to the hormones that could be involved in the onset of maternal behaviour. Oestradiol, progesterone and cortisol concentrations from 4 days before parturition to 24 h after parturition were determined from blood samples collected from 10 calm and 12 nervous ewes. Behavioural interactions between ewe and lamb were also recorded for 2 h starting at parturition. Mothers of both temperament lines showed adequate maternal behaviour under the controlled conditions of the study. Therefore, the results of the study do not suggest that selection for a calm or nervous temperament has profoundly affected the intrinsic ability of mothers to display adequate maternal behaviour. Hormonal differences between the two temperament lines were generally small and their possible influence on the display of maternal behaviour in the two temperament lines would have to be demonstrated.

Stress response in postpartum women with and without obsessive-compulsive symptoms: an fMRI study

BACKGROUND

During the postpartum period, some women might be under a considerable amount of stress and at increased risk for on-set or exacerbation of obsessive-compulsive disorder (OCD). Little is known about the stress response correlates during the postpartum period and in patients with OCD. This study aimed to examine the cerebral, psychologic and endocrine correlates of the stress response in patients with OCD and during the postpartum period.

METHODS

Women with postpartum OCD, healthy postpartum women and healthy mothers past the postpartum period underwent functional magnetic resonance imaging while facing a reliable psychosocial stressor (the Montreal Imaging Stress Task). Stress-related psychologic and endocrine responses (i.e., cortisol) were obtained.

RESULTS

We enrolled 12 women with postpartum OCD, 16 healthy postpartum women and 11 healthy mothers past the postpartum period in our study. Compared with healthy postpartum counterparts, postpartum women with OCD had a heightened self-reported and endocrine stress response associated with a distinct brain activation pattern in response to psychosocial stress involving the orbitofrontal and temporal cortices. Moreover, compared with mothers assessed in a period of time beyond the postpartum period, healthy postpartum women did not differ in psychologic and cortisol response to stress, but recruited different brain regions, such as the dorsolateral prefrontal cortex and the anterior cingulate cortex, during exposure to stress.

LIMITATIONS

Potential confounding factors, such as medication use, breastfeeding, parity and personality factors, may have modulated the stress-related endocrine response and could not be assessed in this study.

CONCLUSION

Obsessive-compulsive disorder and the postpartum period differentially influence the brain circuitry underlying psychosocial stress as well as the psychologic and endocrine responses.

Childbearing, stress and obesity disparities in women: a public health perspective

The perinatal period, from early in the first trimester to 1 year postpartum, provides opportunities for novel public health interventions to reduce obesity disparities. We present a unifying socio-biological framework to suggest opportunities for multidisciplinary research and public health approaches to elucidate and target the mechanisms for the development of maternal obesity and related disparities. The framework illustrates the interplay of the social, cultural and physical environment; stress appraisal and response; and coping behaviors on short-term outcomes (e.g. allostatic load and gestational weight gain), the intermediate outcomes of persistent insulin resistance and post-partum weight retention, and longer term outcomes of obesity and its disease consequences. Testing the proposed relationships may provide insights into how childbearing risk factors such as gestational weight gain, postpartum weight retention and parity contribute to obesity, which are needed to inform public health policies and clinical care guidelines aimed at reducing obesity and improving the health of women.

Maternal programming of reproductive function and behavior in the female rat

Parental investment can be used as a forecast for the environmental conditions in which offspring will develop to adulthood. In the rat, maternal behavior is transmitted to the next generation through epigenetic modifications such as methylation and histone acetylation, resulting in variations in estrogen receptor alpha expression. Natural variations in maternal care also influence the sexual strategy adult females will adopt later in life. Lower levels of maternal care are associated with early onset of puberty as well as increased motivation to mate and greater receptivity toward males during mating. Lower levels of maternal care are also correlated with greater activity of the hypothalamus-pituitary-gonadal axis, responsible for the expression of these behaviors. Contrary to the transition of maternal care, sexual behavior cannot simply be explained by maternal attention, since adoption studies changed the sexual phenotypes of offspring born to low caring mothers but not those from high caring dams. Indeed, mothers showing higher levels of licking/grooming have embryos that are exposed to high testosterone levels during development, and adoption studies suggest that this androgen exposure may protect their offspring from lower levels of maternal care. We propose that in the rat, maternal care and the in utero environment interact to influence the reproductive strategy female offspring display in adulthood and that this favors the species by allowing it to thrive under different environmental conditions.

Hormonal and behavioral responses to stress in lactating and non-lactating female common marmosets (Callithrix jacchus)

In several mammalian species, hypothalamic-pituitary-adrenal (HPA) and behavioral responses to stressors are down-regulated in lactating females, possibly preventing stress-induced disruptions of maternal care. Experimental elevations of HPA axis hormones have been found to inhibit maternal behavior in lactating common marmoset monkeys (Callithrix jacchus), raising the question of whether lactating female marmosets also have blunted endogenous responses to stress. Therefore, we compared HPA and behavioral responses to standardized stressors in reproductively experienced female common marmosets that were undergoing ovulatory cycles and that either were (N=7) or were not lactating (N=8). Each marmoset underwent (1) a restraint stressor during the early follicular phase of the ovarian cycle (approximately 5 weeks postpartum for lactating females) and (2) exposure to a simulated hawk predator during the early to mid-luteal phase (approximately 7 weeks postpartum for lactating females). Lactating females were tested in the presence of one of their infants. Blood samples were collected before, during, and immediately after each test for determination of plasma adrenocorticotropic hormone (ACTH) and cortisol concentrations. Both stressors caused significant elevations in plasma ACTH and cortisol levels, and significant decreases in cortisol:ACTH ratios; however, lactating and non-lactating females showed no significant differences in their endocrine or behavioral responses to either stressor, or in baseline ACTH or cortisol levels. These findings suggest that in contrast to several other mammalian species, lactating female marmosets maintain full behavioral and HPA responsiveness to stress, at least in the presence of their infants.

Effects of reproductive status on behavioral and endocrine responses to acute stress in a biparental rodent, the California mouse (Peromyscus californicus)

In several mammalian species, lactating females show blunted neural, hormonal, and behavioral responses to stressors. It is not known whether new fathers also show stress hyporesponsiveness in species in which males provide infant care. To test this possibility, we determined the effects of male and female reproductive status on stress responsiveness in the biparental, monogamous California mouse (Peromyscus californicus). Breeding (N=8 females, 8 males), nonbreeding (N=10 females, 10 males) and virgin mice (N=12 females, 9 males) were exposed to a 5-min predator-urine stressor at two time points, corresponding to the early postpartum (5-7 days postpartum) and mid/late postpartum (19-21 days postpartum) phases, and blood samples were collected immediately afterwards. Baseline blood samples were obtained 2 days prior to each stress test. Baseline plasma corticosterone (CORT) concentrations did not differ among male or female groups. CORT responses to the stressor did not differ among female reproductive groups, and all three groups showed distinct behavioral responses to predator urine. Virgin males tended to increase their CORT response from the first to the second stress test, while breeding and nonbreeding males did not. Moreover, virgin and nonbreeding males showed significant behavioral changes in response to predator urine, whereas breeding males did not. These results suggest that adrenocortical responses to a repeated stressor in male California mice may be modulated by cohabitation with a female, whereas behavioral responses to stress may be blunted by parental status.

Chronic corticosterone during pregnancy and postpartum affects maternal care, cell proliferation and depressive-like behavior in the dam

Stress during pregnancy and the postpartum can influence the well-being of both the mother and her offspring. Prolonged elevated levels of glucocorticoids are associated with depression and we developed an animal model of postpartum depression/stress based on high levels of corticosterone (CORT) during the postpartum. Gestational stress is a risk factor for postpartum depression and prenatal and/or postnatal high levels of CORT may have differential effects on the mother. Thus the present study was conducted to investigate the effects of low (10mg/kg) or high levels of CORT (40mg/kg) given to dams either during gestation, postpartum or across both gestation and postpartum on maternal care, depressive-like behavior and hippocampal cell proliferation in the dam. Only the high dose of CORT administered during the postpartum increased depressive-like behavior in the dam. Furthermore the high dose of CORT altered maternal care (reduced time spent on the nest and nursing) regardless of whether administration of CORT was during gestation or postpartum. Gestational and/or postpartum treatment with high CORT and postpartum low CORT reduced cell proliferation in the dentate gyrus of postpartum dams compared to oil-treated controls. Thus prolonged treatment with high levels of CORT postpartum reduced maternal care, hippocampal cell proliferation and induced depressive-like behavior in the dam and therefore might be considered an animal model of postpartum depression. More research is needed to understand the effects of stress hormones during different phases of reproduction and how they affect the brain and behavior of the mother and her offspring.

Maternal cortisol in late pregnancy and hypothalamic-pituitary-adrenal reactivity to psychosocial stress postpartum in women

Hypothalamic-pituitary-adrenal (HPA) activity is altered postpartum and has been associated with several puerperal disorders. However, little is known about the association of maternal HPA activity during pregnancy with maternal HPA responsiveness to stress after parturition. Within a longitudinal study with an experimental component, we assessed in 22 women the salivary cortisol awakening response (CAR) at the 36th week of gestation and 6 weeks postpartum, as well as pituitary-adrenal and emotional responses to a psychosocial laboratory stressor at 8 weeks postpartum. CAR in late pregnancy negatively predicted maternal adrenocorticotropin (ACTH; ss = - 0.60; P = 0.003), plasma cortisol (ss = - 0.69, P < 0.001), and salivary cortisol (ss = - 0.66; P = 0.001) but not emotional stress reactivity (all P>0.05) at 8 weeks postpartum, whereas CAR at 6 weeks postpartum failed to predict hormonal (ACTH: ss = 0.02; P = 0.933, plasma cortisol: ss = - 0.23; P = 0.407, salivary cortisol: ss = - 0.15; P = 0.597) or emotional (all P>0.05) stress responses at 8 weeks postpartum. The activity of the HPA axis during pregnancy is associated with maternal HPA responsiveness to stress postpartum. Putative biological underpinnings warrant further attention. A better understanding of stress-related processes peripartum may pave the way for the prevention of associated puerperal disorders.

Effects of elevated circulating cortisol concentrations on maternal behavior in common marmoset monkeys (Callithrix jacchus)

Both acute and chronic stress can impair maternal behavior and increase rates of infant abuse in several species. The mechanisms inducing these effects are unknown, but experimental manipulation of circulating corticosterone levels alters maternal behavior in rats, and circulating or excreted cortisol concentrations have been found to correlate either positively or negatively with maternal behavior in humans and nonhuman primates. In this study, therefore, we experimentally tested the hypothesis that both acute and chronic treatment with exogenous glucocorticoids would alter maternal behavior in a primate, the common marmoset (Callithrix jacchus). Multiparous females, approximately 3-5 weeks postpartum, received daily injections of either cortisol (hydrocortisone sodium succinate and hydrocortisone acetate; N=7) or vehicle (N=7) for 8 days, and maternal behavior was characterized under baseline conditions as well as during exposure to a noise stressor. Cortisol treatment successfully elevated both morning and afternoon plasma cortisol concentrations and suppressed circulating levels of adrenocorticotropic hormone. In home-cage observations, cortisol-treated females carried their infants significantly less than control mothers, and in noise-stressor tests, several hours after the first cortisol or vehicle treatment, cortisol-treated mothers inspected their infants significantly more often than controls. Aggression towards infants was infrequent and mild, and did not differ between treatment groups. These findings provide the first experimental evidence that cortisol elevations can alter maternal behavior in primates. As these effects were limited in scope, however, they suggest that other stress-responsive hormones or neuropeptides may additionally play a role in mediating the effects of stress on maternal behavior.

Predation threat exerts specific effects on rat maternal behaviour and anxiety-related behaviour of male and female offspring

Differences in the rate of maternal behaviours received by rodent offspring are associated with differential programming of molecular and behavioural components of anxiety and stress-related functions. To determine the degree to which maternal behaviours are sensitive to environmental conditions, Long-Evans rat dams were exposed to the odour of a predator (cat) at two different time points during the first week postpartum. Exposure on the day of birth (DOB), but not the third day following birth, increased levels of maternal care in predator-exposed dams relative to dams exposed to a control condition across the first 5 days post-partum. As adults, female offspring of dams exposed on DOB exhibited a less-anxious phenotype in a novel open-field, spending more time in the center and less time displaying thigmotaxis. In contrast, under the same conditions, male offspring showed the opposite behavioural response, consistent with an increasingly anxious phenotype. Results from a subsequent stressor test (response to a predator odour) were consistent with the notion that the rearing effects were specific to anxiety-related behaviours in offspring. Accordingly, we showed that rearing conditions did not affect GR mRNA or NGFI-A expression in the hippocampus of offspring or cross-fostered offspring. The dissociation between stress and anxiety, as well as the sex-specific alterations in behaviour, may reflect the specificity inherent to neural programming in the face of naturalistic early life conditions.

[Attachment process between an infant and his/her mother: the first year]

Attachment theory is focused upon the development of the attachment process organized jointly by the child and the environmental factors which contribute to the development of the feeling of security. The authors focus on the mother-baby relationships and describe the normative process of attachment relationships during the first year of life. The ethologic perspective of this development is also summarized. The steps of the developing attachment relationship are described. The description of motherhood is focused on the bonding process, which is a more immediate and biologically based process and on caregiving which is a symmetrical motivational system as complex as the attachment one. The main factors known as having an impact on the two processes are described.

Effects of uteroplacental insufficiency and reducing litter size on maternal mammary function and postnatal offspring growth

Human intrauterine growth restriction is often associated with uteroplacental insufficiency and a decline in nutrient and oxygen supply to the fetus. This study investigated the effects of uteroplacental insufficiency and intrauterine growth restriction (Restricted) or reducing litter size for normally grown pups (Reduced Litter) on maternal mammary development and function, milk composition, offspring milk intake, and their resultant effects on postnatal growth. Uteroplacental insufficiency was surgically induced by bilateral uterine vessel ligation on day 18 of gestation in the Wistar Kyoto rat. At birth, a group of sham control rats had their litter size reduced to five (Reduced Litter) to match that of the Restricted group. Cohorts of rats were terminally anesthetized on day 20 of gestation or day 6 of lactation, and a third group was studied throughout lactation. Restricted pups had a lower birth weight (by 16%) and litter size (by 36%) compared with controls, as well as reduced mammary parathyroid hormone-related protein content and milk ionic calcium concentrations associated with reduced total pup calcium. Restricted dams with lower circulating progesterone experienced premature lactogenesis, producing less milk per pup with altered composition compared with controls, further slowing growth during lactation. Reducing litter size of pups born of normal birth weight (Reduced Litter) was associated with decreased pup growth, highlighting the importance of appropriate controls. The present study demonstrates that uteroplacental insufficiency impairs mammary function, compromises milk quality and quantity, and reduces calcium transport into milk, further restraining postnatal growth.

Responses of the hypothalamopituitary adrenal axis and the sympathoadrenal system to isolation/restraint stress in sheep of different adiposity

There is evidence that levels of adipose tissue can influence responses of the hypothalamopituitary-adrenal (HPA) axis to stress in humans and rats but this has not been explored in sheep. Also, little is known about the sympathoadrenal responses to stress in individuals with relatively different levels of adipose tissue. We tested the hypothesis that the stress-induced activation of the HPA axis and sympathoadrenal system is lower in ovariectomized ewes with low levels of body fat (lean) than ovariectomized ewes with high levels of body fat (fat). Ewes underwent dietary manipulation for 3 months to yield a group of lean ewes (n = 7) with a mean (+/-SEM) live weight of 39.1 +/- 0.9 kg and body fat of 8.9 +/- 0.6% and fat ewes (n = 7) with a mean (+/-SEM) live weight of 69.0 +/- 1.8 kg and body fat of 31.7 +/- 3.4%. Fat ewes also had higher circulating concentrations of leptin than lean ewes. Blood samples were collected every 15 min over 8 h when no stress was imposed (control day) and on a separate day when 4 h of isolation/restraint was imposed after 4 h of pretreatment sampling (stress day). Plasma concentrations of adrenocorticotropic hormone (ACTH), cortisol, epinephrine and norepinephrine did not change significantly over the control day and did not differ between lean and fat ewes. Stress did not affect plasma leptin levels. All stress hormones increased significantly during isolation/restraint stress. The ACTH, cortisol and epinephrine responses were greater in fat ewes than lean ewes but norepinephrine responses were similar. Our results suggest that relative levels of adipose tissue influence the stress-induced activity of the hypothalamopituitary-adrenal axis and some aspects of the sympathoadrenal system with fat animals having higher responses than lean animals.

Plasma cortisol responses to stress in lactating and nonlactating female rhesus macaques

Lactating female rats without their pups exhibit lower HPA responsiveness to stress than nonlactating females. However, responsiveness to stress is similar when lactating females are tested with their pups and the stressor involves a potential threat to the offspring. This study constitutes the first comparison of stress responsiveness in lactating and nonlactating female nonhuman primates. Subjects were 53 multiparous female free-ranging rhesus macaques. Approximately half of the females were lactating and half were nonpregnant/nonlactating. Blood samples were obtained after capture and after overnight housing in an individual cage. Lactating females were tested with their infants. Lactating females had significantly higher plasma cortisol levels than nonlactating females on both days. Having or not having an infant was also a better predictor of plasma cortisol levels among all females than their age, dominance rank, group of origin, time of day at which the sample was obtained, and time elapsed since beginning of the sampling procedure or since anesthesia. Plasma cortisol levels of lactating females were not significantly correlated with post-partum stage or with the cortisol levels of their infants. Capture, handling, and individual housing in a cage are powerful psychological stressors for free-ranging primates. We suggest that the higher plasma cortisol levels exhibited by lactating females reflect greater responsiveness to stress associated with perception of risks to infants. Hyporesponsiveness to stress may not be a general characteristic of lactation in all mammalian species, but a short-term effect of infant suckling that is most apparent with stressors unrelated to the offspring.

Regulation of anxiety during the postpartum period

Healthy mother-infant interactions are critical for the physical, cognitive, and psychological development of offspring. Such interactions rely on numerous factors, including a positive maternal emotional state. However, many postpartum women experience emotional dysregulation, often involving elevated anxiety. Neuroendocrine factors contributing to the onset of postpartum anxiety symptoms are mostly unknown, but irregularities in hypothalamic-pituitary-adrenal axis function, reduced prolactin and oxytocin signaling, or parturitional withdrawal of ovarian, placental and neural steroids could contribute to anxiety in susceptible women. Although the causes of initial onset are unclear, postpartum anxiety can be mitigated by recent contact with infants. Numerous neurochemical systems, including oxytocin, prolactin, GABA, and norepinephrine mediate this anxiolytic effect of infant contact. Insight into the etiology of postpartum anxiety disorders, and how contact with infants helps counter existing anxiety dysregulation, will surely facilitate the diagnosis and treatment of postpartum women at risk for, or experiencing, an anxiety disorder.

Psychological stressors as a model of maternal adversity: diurnal modulation of corticosterone responses and changes in maternal behavior

Maternal adversity is associated with long-lasting consequences on cognitive development, behavior and physiological responses in rat offspring. Few studies have examined whether repeated maternal stress produces repeated activation of the hypothalamus-pituitary-adrenal (HPA) axis in mothers and whether it modifies maternal behavior. Here, we tested a novel model of perinatal stress using repeated exposure to "purely" psychological stressors throughout the gestation and lactation periods in rats. We first tested the diurnal influences of repeated 1-h strobe light exposure on maternal corticosterone secretion. Despite the hyporesponsiveness to stress documented in late pregnant and lactating mothers, we observed an enhanced response to strobe light in the afternoon compared to the morning in stressed mothers during lactation. Next, dams were exposed to 24-h forced foraging followed by 10-h wet bedding during the diurnal peak of corticosterone secretion. Although no corticosterone responses to forced foraging and wet bedding were observed, the combination of both stressors had a significant effect on maternal behavior. Mother-pup interactions were significantly altered during the first 8 days of lactation. Taken together, these findings suggest that lactating mothers maintain responsiveness to specific and repeated psychological stressors, in particular at the time of the diurnal peak in corticosterone secretion. Depending on the stressor applied, either neuroendocrine activation or changes in maternal behavior might be important determinants of the long-term consequences in the offspring. The combination of forced foraging, wet bedding and strobe light might represent a novel model of mild maternal adversity using "purely" psychological stressors.

High post-partum levels of corticosterone given to dams influence postnatal hippocampal cell proliferation and behavior of offspring: A model of post-partum stress and possible depression

Post-partum stress and depression (PPD) have a significant effect on child development and behavior. Depression is associated with hypercortisolism in humans, and the fluctuating levels of hormones, including corticosterone, during pregnancy and the post-partum, may contribute to PPD. The present study was developed to investigate the effects of high-level corticosterone (CORT) post-partum in the mother on postnatal neurogenesis and behavior in the offspring. Sprague-Dawley dams were treated with either CORT (40 mg/kg) or sesame oil injections daily for 26 days beginning the day after giving birth. Dams were tested in the forced swim test (FST) and in the open field test (OFT) on days 24-26 post-partum. Results showed that the dams exposed to CORT expressed "depressive-like" behavior compared to controls, with decreased struggling behavior and increased immobility in the FST. To investigate the effects of treatment on hippocampal postnatal cell proliferation and survival in the offspring, males and females from treated dams were injected with BrdU (50 mg/kg) on postnatal day 21 and perfused either 24 h (cell proliferation) or 21 days (cell survival) later. Furthermore, male and female offspring from each litter were tested in adulthood on various behavioral tests, including the forced swim test, open field test, resistance to capture test and elevated plus maze. Intriguingly, male, but not female, offspring of CORT-treated dams exhibited decreased postnatal cell proliferation in the dentate gyrus. Both male and female offspring of CORT-treated dams showed higher resistance to capture and greater locomotor activity as assessed in the open field test. As high levels of CORT may be a characteristic of stress and/or depression, these findings support a model of 'CORT-induced' post-partum stress and possibly depression and demonstrate that the offspring of affected dams can exhibit changes in postnatal neurogenesis and behavior in adulthood.

Neuroendocrine mechanisms of innate states of attenuated responsiveness of the hypothalamo-pituitary adrenal axis to stress

Neuroendocrine responses to stress vary between sexes and reproductive states and are influenced by the type of stressor. Stress responses are attenuated in some physiological states, such as lactation and conditions of low visceral adipose tissue. Moreover, some individuals within a species characteristically display reduced stress responses. The neuroendocrine mechanisms for stress hyporesponsiveness are likely to include reduced synthesis and secretion of corticotropin releasing hormone (CRH) and arginine vasopressin (AVP) from the hypothalamus as a result of enhanced glucocorticoid negative feedback and/or reduced noradrenergic stimulatory input from the brain stem. A major limitation of research to date is the lack of direct measures of CRH and AVP secretion. Attenuated stress responsiveness is also commonly associated with reduced pituitary responsiveness to CRH and AVP. The possible roles of inhibitory central inputs to CRH and AVP neurons and of oxytocin and prolactin in attenuating the HPA axis responses to stress are unknown.

Diurnal salivary cortisol levels in postpartum mothers as a function of infant feeding choice and parity

Daily stress and sleep deprivation can influence the diurnal pattern of cortisol, which normally consists of high morning levels and a gradual decline throughout the day. While most individuals have consistent declining cortisol concentrations over days, others display either flat or inconsistent profiles. Postpartum mothers experience considerable home demands and sleep deprivation, yet, breastfeeding mothers perceive lower stress and reduced negative mood states compared to bottlefeeders. On the other hand, multiparity (having more than one child) is associated with reduced steepness in diurnal cortisol decline. Interestingly, no study to date has investigated the diurnal cortisol pattern and its stability across days in postpartum women as a function of their choice of infant feeding and parity. In this study, we measured salivary cortisol at four different time points during the day, on two non-consecutive days in first-time (primiparous) and second-time (multiparous) mothers at 5-20 weeks postpartum who were exclusively breastfeeding or bottlefeeding, and in non-postpartum mothers of young children (1-6 years). Among multiparous mothers, we found that cortisol levels in those who were bottlefeeding were higher than in breastfeeding mothers at both awakening and 1600 h. This effect remained significant after controlling for individual differences related to infant feeding choice, such as estradiol levels, education and income. No effect of infant feeding choice on cortisol concentrations was observed in primiparous mothers. While a consistent decline across days was common, some mothers presented a flat or inconsistent profile, a profile that was not associated with infant feeding choice or parity. Importantly, mothers with consistent declining profiles had the highest household income. Our findings suggest that although breastfeeding might promote a tighter regulation of diurnal basal cortisol secretion, in particular for multiparous mothers who are likely to be exposed to greater home demands and maternal responsibilities, some aspects of socioeconomic status such as income can also play a significant role in the stability of diurnal cortisol secretion across days.

Oxytocin actions within the supraoptic and paraventricular nuclei: differential effects on peripheral and intranuclear vasopressin release

In response to forced swimming (FS), AVP is released somato-dendritically within the supraoptic nucleus (SON) and paraventricular nucleus (PVN), but not from neurohypophyseal terminals into blood. Together with AVP, oxytocin (OXT) is released within the SON and PVN. Here, we studied the role of intra-SON and intra-PVN OXT in the regulation of local AVP release and into the blood in male rats. Within the SON, bilateral retrodialysis of an OXT receptor antagonist (OXT-A) increased local AVP release in response to FS [60 s, 21°C, vehicle twofold, not significant (ns); OXT-A: 15-fold increase, P < 0.05] without significantly affecting basal AVP release. In addition, local OXT-A elevated plasma AVP secretion under basal conditions (twofold increase, P < 0.05) without further elevation after FS. Within the PVN, exposure to FS elevated local AVP release, reaching significance only in the OXT-A group (vehicle: 1.4-fold, ns; OXT-A: 1.6-fold increase, P = 0.050). Bilateral OXT-A into the PVN did not affect peripheral AVP secretion either under basal or stress conditions. Basal ACTH concentrations tended to be elevated by local OXT-A within the PVN (1.7-fold increase, P = 0.076). In contrast, the swim-induced ACTH secretion was attenuated after retrodialysis of OXT-A within both the SON (at 5 min) and PVN (at 15 min) ( P < 0.05 both) compared with vehicle. The results demonstrate a receptor-mediated effect of OXT within the SON and PVN on local and neurohypophyseal AVP release, which depends upon the activity conditions. Further, while exerting an inhibitory effect on hypothalamo-pituitary-adrenal axis activity under basal conditions, hypothalamic OXT is essential for an adequate acute ACTH response.

Multiparity reveals the blunting effect of breastfeeding on physiological reactivity to psychological stress

Rat studies show that hypothalamic-pituitary-adrenal (HPA) responsiveness to physical and emotional stressors is attenuated during lactation, although situations evoking pup endangerment can supersede this phenomenon. In the human population, blunted cortisol responses are seen in primiparous breastfeeding compared to bottlefeeding mothers following physical stress, but not after psychosocial stress. It is currently unknown whether stressor salience (child-related versus nonrelated stressor) has a differential effect on cortisol reactivity as a function of infant feeding choice and whether HPA responses to stress could be modified by parity. We investigated the impact of infant feeding type and maternal parity on salivary cortisol and alpha-amylase response to stress in 5-20-week postpartum mothers using exposure to the Trier Social Stress Test (TSST) and to an emotional film evoking threats to a child. Analyses show that alpha-amylase responses were similar in all groups and for both types of stress, suggesting that sympathetic reactivity was independent of infant feeding type and parity. By contrast, cortisol response was affected by these variables. In primiparous mothers, cortisol reactivity to psychological stressors did not vary as a function of infant feeding type while, among multiparous mothers, breastfeeding was associated with reduced responsiveness to the TSST and child-related stressor. We speculate that changes in neural mechanisms occurring as a result of pregnancy and lactation and that modulate the HPA axis in women might be exacerbated with multiple repeats of the pregnancy/lactation period. This would serve to 'desensitise' stress circuits and reduce the overall stress-induced cortisol secretion after multiple births.

Activation of the hypothalamo-pituitary-adrenal axis by isolation and restraint stress during lactation in ewes: effect of the presence of the lamb and suckling

We investigated the effect of the presence and absence of lambs and suckling by lambs to attenuate activation of the hypothalamo-pituitary-adrenal (HPA) axis to isolation and restraint stress in lactating sheep. In experiment 1, blood samples were collected every 10 min from nonlactating (n = 5) and lactating (n = 5) ewes for 4 h before and during stress. In experiment 2, ewes (n = 6) were allocated to 1) nonlactating, 2) lactating with lambs absent, 3) lactating with lambs present but unable to suckle, and 4) lactating with lambs present and able to suckle. Blood samples were collected over 8 h with no stress (control day) and for 4 h before and 4 h during stress (stress day). In experiment 1, the mean (+/-SEM) cortisol concentrations increased significantly (P < 0.05) in nonlactating ewes during stress but did not change in lactating ewes. In experiment 2, cortisol did not vary on the control day or pretreatment of the stress day but increased (P < 0.05) during stress in all groups except lactating ewes with lambs present and able to suckle. The greatest cortisol response occurred in nonlactating ewes followed by lactating ewes with lambs absent and lactating ewes with lambs present but unable to suckle. During stress, the ACTH concentrations increased (P < 0.05) in nonlactating ewes and lactating ewes with lambs absent but not in lactating ewes with lambs present. We conclude that the activity of the HPA axis during isolation and restraint is reduced in lactating ewes and that the presence of lambs increases this level of attenuation.