Prolactin mitigates chronic stress-induced maladaptive behaviors and physiology in ovariectomized female rats.

Stress is a major risk factor for several neuropsychiatric disorders in women, including postpartum depression. During the postpartum period, diminished ovarian hormone secretion increases susceptibility to developing depressive symptoms. Pleiotropic peptide hormones, like prolactin, are markedly released during lactation and suppress hypothalamic-pituitary-adrenal axis responses in women and acute stress-induced behavioral responses in female rodents.

Lactation is not required for maintaining maternal care and active coping responses in chronically stressed postpartum rats: Interactions between nursing demand and chronic variable stress.

Women who do not breastfeed or discontinue breastfeeding early are more likely to develop postpartum depression (PPD) and stress is a significant risk factor for depression, including PPD. Using a rat model, we investigated whether the absence of nursing would increase the susceptibility to chronic stress-related behavioral and neural changes during the postpartum period. Adult female rats underwent thelectomy (thel; removal of teats), sham surgery, or no surgery (control) and were paired with males for breeding.

Rotated nursing environment with underfeeding: A form of early-life adversity with sex- and age-dependent effects on coping behavior and hippocampal neurogenesis.

We investigated how a unique form of early-life adversity (ELA), caused by rotated nursing environment to induce underfeeding, alters anxiety-like and stress-coping behaviors in male and female Sprague Dawley rats in adolescence and adulthood. Adult female rats underwent either thelectomy (thel; surgical removal of teats), sham surgery, or no surgery (control) before mating. Following parturition, litters were rotated between sham and thel rats every 12 h to generate a group of rats that experienced ELA (rotated housing, rotated mother, and 50% food restriction) from postnatal day 0 to 26.

Maternal experience and adult neurogenesis in mammals: Implications for maternal care, cognition, and mental health.

The transition to motherhood encompasses physiological and behavioral adaptations essential for the initiation and maintenance of offspring care and feeding and includes widespread changes throughout the brain. The growth of new neurons occurs across the lifespan in distinct regions of mammalian brains and changes dynamically across reproductive events in female mammals. The subventricular zone (SVZ) and dentate gyrus (DG) of the hippocampus undergo high rates of neurogenesis in adulthood and are sensitive to hormonal fluctuations.

High nursing demand reduces depression-like behavior despite increasing glucocorticoid concentrations and reducing hippocampal neurogenesis in late postpartum rats.

Approximately 15% of women who give birth develop postpartum depression (PPD), and the risk is greater in women who do not breastfeed or who cease breastfeeding early. In some women, early cessation or absence of breastfeeding precedes PPD, but the neuroendocrine mechanisms of this relationship are unknown. We tested whether nursing demand would alter behavioral and endocrine endpoints relevant for depression in postpartum rats.

Voluntary running influences the efficacy of fluoxetine in a model of postpartum depression.

Postpartum depression affects approximately 15% of mothers. Unfortunately, treatment options for postpartum depression are limited. Pharmacological antidepressants such as fluoxetine (FLX) can be controversial due to inconclusive evidence of efficacy during the postpartum and concerns of neonatal exposure to antidepressants.

Sex-dependent effects of maternal corticosterone and SSRI treatment on hippocampal neurogenesis across development.

Background: Postpartum depression affects approximately 15% of mothers and represents a form of early life adversity for developing offspring. Postpartum depression can be treated with prescription antidepressants like fluoxetine (FLX). However, FLX can remain active in breast milk, raising concerns about the consequences of neonatal FLX exposure.

Parity modifies the effects of fluoxetine and corticosterone on behavior, stress reactivity, and hippocampal neurogenesis.

The postpartum confers considerable risk for developing depression. Depressed patients have elevated cortisol concentrations and impaired hypothalamic-pituitary-adrenal (HPA) axis negative feedback. Chronic stress or corticosterone (CORT) induces a depressive-like phenotype in rodents, including during the postpartum.

Testosterone has antidepressant-like efficacy and facilitates imipramine-induced neuroplasticity in male rats exposed to chronic unpredictable stress.

Hypogonadal men are more likely to develop depression, while testosterone supplementation shows antidepressant-like effects in hypogonadal men and facilitates antidepressant efficacy. Depression is associated with hypothalamic-pituitary-adrenal (HPA) axis hyperactivity and testosterone exerts suppressive effects on the HPA axis. The hippocampus also plays a role in the feedback regulation of the HPA axis, and depressed patients show reduced hippocampal neuroplasticity.

Maternal postpartum corticosterone and fluoxetine differentially affect adult male and female offspring on anxiety-like behavior, stress reactivity, and hippocampal neurogenesis.

Postpartum depression (PPD) affects approximately 15% of mothers, disrupts maternal care, and can represent a form of early life adversity for the developing offspring. Intriguingly, male and female offspring are differentially vulnerable to the effects of PPD. Antidepressants, such as fluoxetine, are commonly prescribed for treating PPD.

Alcohol and pregnancy: Effects on maternal care, HPA axis function, and hippocampal neurogenesis in adult females.

Chronic alcohol consumption negatively affects health, and has additional consequences if consumption occurs during pregnancy as prenatal alcohol exposure adversely affects offspring development. While much is known on the effects of prenatal alcohol exposure in offspring less is known about effects of alcohol in dams. Here, we examine whether chronic alcohol consumption during gestation alters maternal behavior, hippocampal neurogenesis and HPA axis activity in late postpartum female rats compared with nulliparous rats.

Prior high corticosterone exposure reduces activation of immature neurons in the ventral hippocampus in response to spatial and nonspatial memory.

Chronic stress or chronically high glucocorticoids attenuate adult hippocampal neurogenesis by reducing cell proliferation, survival, and differentiation in male rodents. Neurons are still produced in the dentate gyrus during chronically high glucocorticoids, but it is not known whether these new neurons are appropriately activated in response to spatial memory. Thus, the goal of this study was to determine whether immature granule neurons generated during chronically high glucocorticoids (resulting in a depressive-like phenotype) are differentially activated by spatial memory retrieval.

Sex differences in the HPA axis.

The hypothalamic-pituitary-adrenal (HPA) axis is a major component of the systems that respond to stress, by coordinating the neuroendocrine and autonomic responses. Tightly controlled regulation of HPA responses is critical for maintaining mental and physical health, as hyper- and hypo-activity have been linked to disease states. A long history of research has revealed sex differences in numerous components of the HPA stress system and its responses, which may partially form the basis for sex disparities in disease development.

Reproductive experience does not persistently alter prefrontal cortical-dependent learning but does alter strategy use dependent on estrous phase.

Reproductive experiences in females comprise substantial hormonal and experiential changes and can exert long lasting changes in cognitive function, stress physiology, and brain plasticity. The goal of this research was to determine whether prior reproductive experience could alter a prefrontal-cortical dependent form of learning (strategy set shifting) in an operant box. In this study, female Sprague-Dawley rats were mated and mothered once or twice to produce either primiparous or biparous dams, respectively.

Endocrine substrates of cognitive and affective changes during pregnancy and postpartum.

Pregnancy and motherhood constitute periods of tremendous hormonal variation that orchestrate parturition, lactation, maternal care, maternal aggression, and recognition of offspring, among other functions. Cognitive processing also varies during pregnancy and motherhood and may serve an adaptive function in preparation for parturition and rearing. Additionally, maternal experience may have enduring consequences for the brain, behavior, and cognition long after offspring are mature.

Short day lengths alter stress and depressive-like responses, and hippocampal morphology in Siberian hamsters.

Many psychological disorders comprise a seasonal component. For instance, seasonal affective disorder (SAD) is characterized by depression during autumn and winter. Because hippocampal atrophy may underlie the symptoms of depression and depressive-like behaviors, one goal of this study was to determine whether short days also induce structural changes in the hippocampus using photoperiod responsive rodents--Siberian hamsters.

Post-weaning environmental enrichment alters affective responses and interacts with behavioral testing to alter nNOS immunoreactivity.

Challenging early life events can dramatically affect mental health and wellbeing. Childhood trauma and neglect can increase the risk for developing depressive, anxiety, and substance abuse disorders. Early maternal separation in rodents has been extensively studied and induces long-lasting alterations in affective and stress responses.

Dietary arginine depletion reduces depressive-like responses in male, but not female, mice.

Previous behavioral studies have manipulated nitric oxide (NO) production either by pharmacological inhibition of its synthetic enzyme, nitric oxide synthase (NOS), or by deletion of the genes that code for NOS. However manipulation of dietary intake of the NO precursor, L-arginine, has been understudied in regard to behavioral regulation. L-Arginine is a common amino acid present in many mammalian diets and is essential during development.

Short photoperiods alter cannabinoid receptor expression in hypothalamic nuclei related to energy balance.

This study examined the photoperiodic regulation of energy balance and cannabinoid receptor expression in the Siberian hamster (Phodopus sungorus) hypothalamus. Short day lengths, beginning at weaning, reduced food intake, body mass and fat pad masses and also decreased cannabinoid receptor immunostaining in the anterior and lateral hypothalamic nuclei of male hamsters. These data suggest a potential role for reduced cannabinoid drive in mediating short day-induced alterations in energy balance.

Light at night increases body mass by shifting the time of food intake.

The global increase in the prevalence of obesity and metabolic disorders coincides with the increase of exposure to light at night (LAN) and shift work. Circadian regulation of energy homeostasis is controlled by an endogenous biological clock that is synchronized by light information. To promote optimal adaptive functioning, the circadian clock prepares individuals for predictable events such as food availability and sleep, and disruption of clock function causes circadian and metabolic disturbances.

Potential animal models of seasonal affective disorder.

Seasonal affective disorder (SAD) is characterized by depressive episodes during winter that are alleviated during summer and by morning bright light treatment. Currently, there is no animal model of SAD. However, it may be possible to use rodents that respond to day length (photoperiod) to understand how photoperiod can shape the brain and behavior in humans.

Environmental enrichment enhances delayed-type hypersensitivity in both short- and long-day Siberian hamsters.

Darwinian fitness reflects trade-offs between reproduction and survival. Mechanisms have evolved in small nontropical mammals and birds to maximize reproductive output during the summer when thermoregulatory demands are relatively low and food is abundant and to shunt energy to processes that presumably increase the odds of survival during the winter when thermoregulatory demands are high and food is scarce. In order to predict the onset of winter, many seasonally-breeding mammals use day length (photoperiod) information.

Short day lengths skew prenatal sex ratios toward males in Siberian hamsters.

For decades, researchers have documented significant skews in the production of male versus female offspring in many species. Because males and females are differentially susceptible to environmental challenges and also represent different fitness benefits, it may be beneficial to exert control over the offspring sex ratio when environmental conditions become challenging. Some of the most dramatic environmental challenges occur on a seasonal basis.

Influence of light at night on murine anxiety- and depressive-like responses.

Individuals are increasingly exposed to light at night. Exposure to constant light (LL) disrupts circadian rhythms of locomotor activity, body temperature, hormones, and the sleep-wake cycle in animals. Other behavioural responses to LL have been reported, but are inconsistent.

Enrichment and photoperiod interact to affect spatial learning and hippocampal dendritic morphology in white-footed mice (Peromyscus leucopus).

In seasonally changing environments, individuals must coordinate endogenous processes with ambient conditions. Winter is a challenging time to survive and reproduce. In order to anticipate decreased food availability and low temperatures in winter, many rodents use decreasing day lengths as a precise temporal cue.