Glucocorticoids disrupt neuroendocrine and behavioral responses during lactation

Exposure to the psychedelic substance 25 H-NBOMe disrupts maternal care in lactating rats and subsequently impairs the social play behavior of the offspring

Given the critical role of maternal care in the neurodevelopment of offspring, this study aimed to investigate the effects of the psychedelic substance 25 H-NBOMe on maternal behavior in lactating rats and its subsequent impact on the social and neurodevelopmental behavior of the offspring. We administered two different dosages of 25 H-NBOMe (0.3 mg/kg and 1.0 mg/kg; i,p,) to lactating rats and observed changes in maternal behaviors, such as nest-building and pup retrieval, and in offspring behaviors, including social play. Behavioral assessments were complemented by physiological measurements to rule out general health or nutritional decline. 25 H-NBOMe significantly disrupted maternal behaviors, including nest-building and pup retrieval, without affecting the weight of dams or offspring. Offspring of exposed dams exhibited reduced social play behavior. Higher doses led to more pronounced disruptions, while lower doses, despite not visibly affecting maternal behavior, still impacted offspring behavior, suggesting potential direct effects of 25 H-NBOMe. The study highlights the potential risks associated with the use of 25 H-NBOMe during lactation, emphasizing its detrimental impact on maternal care and offspring development. These findings contribute to understanding the neurobiological effects of psychedelic substances during critical developmental periods and underscore the importance of avoiding their use.

Acute and chronic sleep restriction differentially modify maternal behavior and milk macronutrient composition in the postpartum rat

BACKGROUNDS

Sleep restriction is considered a stressful condition itself, causing a wide variety of physiological alterations, from cognitive and hormonal to immunological status. In addition, it is established that stress in mother rats can modify milk ejection, milk composition, and maternal care of the pups. Also, sleep disturbances during the early stages of motherhood are a common feature of all studied species. In this context, while the impacts of sleep disruption in non-lactating animals were extensively investigated, its repercussions during the initial phases of motherhood have been poorly explored. Therefore, we wonder if maternal behavior, milk ejection and its macronutrient composition would be disrupted when mother rats are subjected to an additional acute or chronic sleep restriction to the already existing sleep disturbances.

METHODS

Lactating rats were implanted with unilateral electrodes for polysomnographic recordings and for deep brain electrical stimulation into mesopontine waking-promoting area (for sleep deprivation). During the early postpartum period (postpartum day 5-9), mother rats were randomly assigned into one of three groups: chronic sleep restriction group (CSR; 6 h of sleep deprivation/day for five consecutive days), acute sleep restriction group (ASR; 6 h of sleep deprivation only for one day), or undisturbed group (control group). Active maternal behaviors (retrievals of the pups into the nest, mouthing, lickings [corporal and anogenital] and sniffing the pups) and passive maternal behaviors (kyphotic and supine nursing postures) were evaluated during a 30 min period without sleep restriction immediately after the sleep restriction or control period. The litter weight gain was assessed every day, and on the last experimental session mothers were milked for posterior macronutrients analysis (protein, carbohydrates and fat).

RESULTS

When compared to control group, CSR decreased the amount of milk ejected in the middle days of the sleep restriction period, while ASR did not affect this parameter. Moreover, ASR reduced milk protein content compared to control and CSR groups. Finally, compared to the control group, CSR reduced active maternal behaviors towards the end of the treatment days.

CONCLUSIONS

We demonstrated that not only acute but also chronic sleep restriction impacts on the postpartum period, each one affecting different aspects of maternal behavior and lactation. Our results suggest the existence of a homeostatic recovery mechanism in breastfeeding during CSR, possibly ensuring the survival of the litter, while the decline in active maternal behaviors appears to be cumulative.

Litter reduction-induced obesity promotes early depressive-like behavior and elevated prefrontal cortex GFAP expression in male offspring

AIMS

The present study was developed to investigate how litter reduction-induced obesity promotes early depressive-related behaviors in rodent offspring.

MAIN METHODS

We employed a standardized litter size reduction protocol, dividing litters into groups: normal litters (NL), consisting of six males and six females pups and small litters (SL), comprising two males and two females pups. Maternal behavior was monitored during the initial week of lactation. Subsequently, we assessed the pups for weight gain, locomotor activity, social play behavior, and performance in forced swimming test. We further evaluated the weights of retroperitoneal and perigonadal fat tissues, along with the expression of glial fibrillary acidic pprotein (GFAP) in the hippocampus and prefrontal cortex of the offspring.

KEY FINDINGS

Our results indicated that litter size reduction led to an increased the maternal behavior. In contrast, offspring from the SL group displayed greater weight gain and increased, retroperitoneal and perigonadal fat. Both male and female rodents in the SL group exhibited decreased social play behavior, and male offspring spent more time immobile during the forced swimming test, suggesting a depressive-like phenotype. Notably, we observed an increase in the GFAP expression in the prefrontal cortex of male rodents, with a trend toward increased expression in the hippocampus.

SIGNIFICANCE

Obesity may facilitate the development of early depressive-like behaviors, potentially associated with elevated GFAP expression in the prefrontal cortex.

Chronic Stress Decreases Lactation Performance

The ability to provision offspring with milk is a significant adaptive feature of mammals that allows for considerable maternal regulation of offspring beyond gestation, as milk provides complete nutrition for developing neonates. For mothers, lactation is a period of marked increases in energetic and nutritive demands to support milk synthesis; because of this considerable increase in demand imposed on multiple physiological systems, lactation is particularly susceptible to the effects of chronic stress. Here, we present work that explores the impact of chronic stress during lactation on maternal lactation performance (i.e., milk quality and quantity) and the expression of key milk synthesis genes in mammary tissue using a Sprague-Dawley rat model. We induced chronic stress using a well-established, ethologically relevant novel male intruder paradigm for 10 consecutive days during the postpartum period. We hypothesized that the increased energetic burden of mounting a chronic stress response during lactation would decrease lactation performance. Specifically, we predicted that chronic exposure to this social stressor would decrease either milk quality (i.e., composition of proximate components and energy density) or quantity. We also predicted that changes in proximate composition (i.e., lipid, lactose, and protein concentrations) would be associated with changes in gene expression levels of milk synthesis genes. Our results supported our hypothesis that chronic stress impairs lactation performance. Relative to the controls, chronically stressed rats had lower milk yields. We also found that milk quality was decreased; milk from chronically stressed mothers had lower lipid concentration and lower energy density, though protein and lactose concentrations were not different between treatment groups. Although there was a change in proximate composition, chronic stress did not impact mammary gland expression of key milk synthesis genes. Together, this work demonstrates that exposure to a chronic stressor impacts lactation performance, which in turn has the potential to impact offspring development via maternal effects.

Toward reframing brain-social dynamics: current assumptions and future challenges

Evolutionary analyses suggest that the human social brain and sociality appeared together. The two fundamental tools that accelerated the concurrent emergence of the social brain and sociality include learning and plasticity. The prevailing core idea is that the primate brain and the cortex in particular became reorganised over the course of evolution to facilitate dynamic adaptation to ongoing changes in physical and social environments. Encouraged by computational or survival demands or even by instinctual drives for living in social groups, the brain eventually learned how to learn from social experience via its massive plastic capacity. A fundamental framework for modeling these orchestrated dynamic responses is that social plasticity relies upon neuroplasticity. In the present article, we first provide a glimpse into the concepts of plasticity, experience, with emphasis on social experience. We then acknowledge and integrate the current theoretical concepts to highlight five key intertwined assumptions within social neuroscience that underlie empirical approaches for explaining the brain-social dynamics. We suggest that this epistemological view provides key insights into the ontology of current conceptual frameworks driving future research to successfully deal with new challenges and possible caveats in favour of the formulation of novel assumptions. In the light of contemporary societal challenges, such as global pandemics, natural disasters, violent conflict, and other human tragedies, discovering the mechanisms of social brain plasticity will provide new approaches to support adaptive brain plasticity and social resilience.

The contributions of parental lactation on offspring development: It's not udder nonsense!

The Developmental Origins of Health and Disease (DOHaD) hypothesis describes how maternal stress exposures experienced during critical periods of perinatal life are linked to altered developmental trajectories in offspring. Perinatal stress also induces changes in lactogenesis, milk volume, maternal care, and the nutritive and non-nutritive components of milk, affecting short and long-term developmental outcomes in offspring. For instance, selective early life stressors shape the contents of milk, including macro/micronutrients, immune components, microbiota, enzymes, hormones, milk-derived extracellular vesicles, and milk microRNAs. In this review, we highlight the contributions of parental lactation to offspring development by examining changes in the composition of breast milk in response to three well-characterized maternal stressors: nutritive stress, immune stress, and psychological stress. We discuss recent findings in human, animal, and in vitro models, their clinical relevance, study limitations, and potential therapeutic significance to improving human health and infant survival. We also discuss the benefits of enrichment methods and support tools that can be used to improve milk quality and volume as well as related developmental outcomes in offspring. Lastly, we use evidence-based primary literature to convey that even though select maternal stressors may modulate lactation biology (by influencing milk composition) depending on the severity and length of exposure, exclusive and/or prolonged milk feeding may attenuate the negative in utero effects of early life stressors and promote healthy developmental trajectories. Overall, scientific evidence supports lactation to be protective against nutritive and immune stressors, but the benefits of lactation in response to psychological stressors need further investigation.

Sex-specific stress and biobehavioral responses to human experimenters in rats

Important factors influencing the outcome of animal experiments in preclinical research are often overlooked. In the current study, the reaction of female and male rats toward the biological sex of a human experimenter was investigated in terms of anxiety-like behaviors and physiological stress responses, as measured by infrared (IR) thermography, circulating corticosterone (CORT) and oxytocin levels. Female rats displayed consistently exacerbated anxiety-related behaviors along with elevated body surface temperature during repeated exposure to male experimenters. Experimental stress further intensified thermal responses to a male experimenter, especially in female rats. The behavioral responses to a male experimenter in females were associated with higher circulating CORT and lower oxytocin levels. Similar responses were induced by a T-shirt worn by a human male. The findings suggest that psychophysiological responses of female rats to a male experimenter are influenced by both visual and olfactory cues. The results emphasize the need to not only consider sex differences in experimental animals, but also standardize and report the experimenter’s biological sex to avoid ambiguity in the generation and interpretation of results.

Maternal glucocorticoids have minimal effects on HPA axis activity and behavior of juvenile wild North American red squirrels

As a response to environmental cues, maternal glucocorticoids (GCs) may trigger adaptive developmental plasticity in the physiology and behavior of offspring. In North American red squirrels (Tamiasciurus hudsonicus), mothers exhibit increased GCs when conspecific density is elevated, and selection favors more aggressive and perhaps more active mothers under these conditions. We tested the hypothesis that elevated maternal GCs cause shifts in offspring behavior that may prepare them for high-density conditions. We experimentally elevated maternal GCs during gestation or early lactation. We measured two behavioral traits (activity and aggression) in weaned offspring using standardized behavioral assays. Because maternal GCs may influence offspring hypothalamic-pituitary-adrenal (HPA) axis dynamics, which may in turn affect behavior, we also measured the impact of our treatments on offspring HPA axis dynamics (adrenal reactivity and negative feedback), and the association between offspring HPA axis dynamics and behavior. Increased maternal GCs during lactation, but not gestation, slightly elevated activity levels in offspring. Offspring aggression and adrenal reactivity did not differ between treatment groups. Male, but not female, offspring from mothers treated with GCs during pregnancy exhibited stronger negative feedback compared with those from control mothers, but there were no differences in negative feedback between lactation treatment groups. Offspring with higher adrenal reactivity from mothers treated during pregnancy (both controls and GC-treated) exhibited lower aggression and activity. These results suggest that maternal GCs during gestation or early lactation alone may not be a sufficient cue to produce substantial changes in behavioral and physiological stress responses in offspring in natural populations.

Anxiety-like behavior and neuroendocrine changes in offspring resulting from gestational post-traumatic stress disorder

Exposure to stressful environmental events during the perinatal period can increase vulnerability to psychopathologies that cause neuroendocrine changes associated with deficits in emotional behavior that can appear early in life. Post-traumatic stress disorder (PTSD) is a frequent, chronic, and disabling disorder that negatively impacts the emotional, social, and cognitive behaviors of affected individuals. Thus, we induced PTSD in pregnant rats by applying inescapable footshocks and then investigated the behavioral parameters similar to anxiety in offspring at prepubertal age, in addition to the plasma levels of maternal and offspring corticosterone and expression of glucocorticoid receptors (GR) in the offspring's hippocampus. With the dams, maternal behavior, open field, and object recognition tests were performed. With the male and female offspring, we performed the following: quantification of ultrasonic vocalizations, elevated plus-maze test, evaluation of exploratory activity in the open field, and hole board test, as well as plasma corticosterone measurements and Western blotting for GR. Our results showed that gestational PTSD affected maternal behavior, led to anxiety-like symptoms, increased corticosterone levels, and increased GR expression in the offspring's hippocampus. Therefore, our data can contribute to the understanding of the onset of early (childhood and juvenile/pre-pubertal phases) anxiety owing to exposure to a traumatic event during the gestation period.

Gestational exposure to excessive levels of dexamethasone impairs maternal care and impacts on the offspring's survival in rats

Administration of dexamethasone (DEX) during late gestation is a model to study growth restriction in rodents, but the pup's mortality index can be high, depending on DEX dosage, and little is known about the effects of DEX on maternal care (MC). Considering that an inadequate MC can also contribute to pup's mortality in this model, we evaluated the effects of DEX on dams' behavior and its consequences on offspring survival. We also investigated whether the cross-fostering of pups from dams treated or not with DEX could improve pup's survival. Wistar rats were treated with DEX (14th to 19th day of gestation -0.2 mg/kg, B.W, in the drinking water). Nest building, MC and responses in the elevated plus-maze, forced swimming and object recognition tests were evaluated. DEX reduced gestational weight gain and impaired neonatal development, reducing pup's survival to 0% by the 3rd postnatal day. DEX-treated dams reduced the expression of typical MC and increased anxiety-like behaviors. After cross-fostering, DEX-treated mothers behaved similarly to controls, indicating that a healthy offspring is crucial to induce adequate MC. Cross-fostering increased the survival index from zero to 25% in the DEX offspring. Postnatal development of the DEX offspring was comparable to controls after cross-fostering. We concluded that exposure to DEX during late gestation causes behavioral changes that compromise the maternal emotional state, disrupting the expression of MC. Although it does not seem to be the main cause of pup's mortality, our data indicate that an adequate MC improves pup's survival in this model.

Maternal social environment affects offspring cognition through behavioural and immune pathways in rats

The social environment of lactation is a key etiological factor for the occurrence of postpartum disorders affecting women and their children. Postpartum depression and anxiety disorders are highly prevalent in new mothers and negatively affect offspring's cognitive development through mechanisms which are still unclear. Here, using a rat model, we manipulated the maternal social environment during lactation and explored the pathways through which social isolation (vs. the opportunity for limited social interaction with another lactating female, from 1 day before parturition to postpartum day 16) and chronic social conflict (daily exposure to a male intruder from postpartum day 2 to day 16) affect offspring learning and memory, measured at 40 to 60 days of age. We specifically explored the consequences of these social treatments on two main hypothesized mediators likely to affect offspring neurophysiological development: the quality of maternal care and maternal inflammation factors (brain-derived neurotrophic factor, granulocyte-macrophage colony-stimulating factor, intercellular adhesion molecule 1, tissue inhibitor of metalloproteinases 1 and vascular endothelial growth factor) likely to influence offspring development through lactation. Maternal rats which had the opportunity to interact with another lactating female spent more time with their pups which, in turn, displayed improved working and reference memory. Social stress affected maternal plasma levels of cytokines that were associated with cognitive deficits in their offspring. However, females subjected to social stress were protected from these stress-induced immune changes and associated offspring cognitive impairment by increased social affiliation. These results underscore the effects of social interaction for new mothers and their offspring and can be used to inform the development of clinical preventative measures and interventions.

P2 purinergic receptor antagonists disrupt maternal behavior in lactating rats

The involvement of purinergic signaling in several brain functions has been recognized, but the modulation on maternal behavior by the purinergic system is not established, even though there are functional interactions between the purinergic and oxytocinergic systems. Therefore, the aim of our study was to investigate whether central administration of P2 receptor antagonists affected the maternal behavior of lactating rats and c-Fos immunoreactivity in the forebrain. On day 7 of lactation, female rats were treated with vehicle (5μL; i.c.v.), suramin (9.4-75.0μg/5μL; i.c.v.) or PPADS (9.4-75.0μg/5μL; i.c.v.) 30min before the experiment began. The maternal behavior was evaluated during the 30min following suramin or PPADS administration. In addition, c-Fos-positive nuclei were counted in the medial preoptic area (MPOA) and in the bed nucleus of the stria terminalis (BNST), and neurons that were double-labeled for c-Fos/OT were counted in the paraventricular nucleus (PVN) and supraoptic nucleus (SON) of the hypothalamus of lactating rats. The results show that P2 receptor antagonists decreased maternal care and decreased neuronal activation in the MPOA and BNST and activation of oxytocinergic neurons in hypothalamic nuclei. Our results indicate that the purinergic system modulates maternal behavior and neuronal activation induced by suckling during lactation.

Corticosteroid Injections: A Review of Sex-Related Side Effects

Corticosteroid injections are used as a nonoperative modality to combat acute inflammation when conservative treatments fail. As female patients are regularly seen by orthopedic physicians, it is essential to identify and understand potential sex-related side effects. The aim of this article is to examine available literature for sex-related side effects of orthopedic-related corticosteroid injections. Although the incidence is low, sex-related side effects, such as abnormal menstruation, lactation disturbances, facial flushing, and hirsutism, are associated with corticosteroid injections. Physicians should be aware of these female-specific side effects and relay this information as part of the informed consent process. [Orthopedics. 2017; 40(2):e211-e215.].

Relationship between glucocorticoids and prolactin during mammary gland stimulation in dairy cows

The objectives of this study were to determine the role of glucocorticoids in the regulation of prolactin (PRL) release induced by mammary gland stimulation and to investigate whether the milk depression induced by glucocorticoids in dairy cows is due to a decrease in PRL release. In experiment 1, 8 dairy cows were used in a 4 × 4 Latin square design. Four hours after the morning milking, the cows received 1 of the following treatments: (1) a 5-min manual stimulation of the mammary gland; (2) an i.v. injection of 1 mg of dexamethasone; (3) 2 infusions of 2.5 g of metyrapone (an inhibitor of cortisol biosynthesis) in the omasum 4 and 2 h before a 5-min stimulation of the mammary gland; or (4) no treatment. Sixty minutes later, the mammary gland of each cow was stimulated for 5 min. Blood samples were collected from 20 min before to 120 min after the start of the treatment. When the mammary gland was stimulated twice in 60 min, less PRL and cortisol were released during the second stimulation. Metyrapone did not affect PRL or cortisol release. Dexamethasone decreased serum cortisol concentration but did not affect PRL concentration. In experiment 2, 16 cows were used in a crossover experimental design consisting of 2 experimental weeks separated by 1 resting week. During the first week, cows were treated as follows: (1) 4 cows were injected with 0.5 g of domperidone (a PRL secretagogue) in canola oil on d 1 and 2 and 20 mg of dexamethasone on d 1; (2) 4 cows were injected with 0.5 g of domperidone on d 1 and 2; (3) 4 cows were injected with canola oil on d 1 and 2 and with 20 mg of dexamethasone on d 1; and (4) 4 cows were injected with canola oil on d 1 and 2. During the second experimental week, the same 4 treatments were repeated, except the cows that did not receive dexamethasone in the first week received it on d 1 of the second week, and cows that did receive it in the first week did not receive it in the second week. On d 1 and 2 of each week, blood samples were collected during morning milking for PRL determination. Dexamethasone reduced milk production and decreased both basal and milking-induced PRL release. It also increased milk fat and protein percentages and decreased milk lactose content. Domperidone increased basal PRL levels in serum and milk but did not affect milk yield. Although we cannot rule out the possibility that inhibition of PRL secretion or reduction of mammary gland PRL responsiveness play a role in the inhibition of milk production by glucocorticoids, the fact that enhancement of PRL secretion by domperidone could not prevent the depression of milk yield suggests that other mechanisms are involved.

Haploinsufficiency for Steroidogenic Factor 1 Affects Maternal Behavior in Mice

Steroidogenic factor 1 (SF-1), officially designated NR5A1, is essential for gonadal and adrenal development and for the normal structure of the ventromedial hypothalamus (VMH), as demonstrated by SF-1 knockout mice (SF-1 KO), but much less is known about the possible effects of haploinsufficiency of the SF-1 gene. In the present study, maternal behavior in SF-1 KO heterozygous mice was evaluated. Behavioral tests revealed that SF-1 KO heterozygous females have impaired maternal behavior. In comparison to wild-type (WT) females, SF-1 KO heterozygous females retrieved significantly fewer pups into their nests, latency to retrieve and crouch over the pups was longer, and their nests were lower quality. As suggested by previous studies full dosage of SF-1 gene is needed for appropriate stress response and expression of brain-derived neurotrophic factor (BDNF) in the brain, and this might present a mechanism through which maternal behavior in SF-1 KO heterozygous females is impaired.

Endocannabinoid Regulation of Neuroendocrine Systems

The hypothalamus is a part of the brain that is critical for sustaining life through its homeostatic control and integrative regulation of the autonomic nervous system and neuroendocrine systems. Neuroendocrine function in mammals is mediated mainly through the control of pituitary hormone secretion by diverse neuroendocrine cell groups in the hypothalamus. Cannabinoid receptors are expressed throughout the hypothalamus, and endocannabinoids have been found to exert pronounced regulatory effects on neuroendocrine function via modulation of the outputs of several neuroendocrine systems. Here, we review the physiological regulation of neuroendocrine function by endocannabinoids, focusing on the role of endocannabinoids in the neuroendocrine regulation of the stress response, food intake, fluid homeostasis, and reproductive function. Cannabis sativa (marijuana) has a long history of recreational and/or medicinal use dating back to ancient times. It was used as an analgesic, anesthetic, and antianxiety herb as early as 2600 B.C. The hedonic, anxiolytic, and mood-elevating properties of cannabis have also been cited in ancient records from different cultures. However, it was not until 1964 that the psychoactive constituent of cannabis, Δ(9)-tetrahydrocannabinol, was isolated and its chemical structure determined (Gaoni & Mechoulam, 1964).

Central corticosterone disrupts behavioral and neuroendocrine responses during lactation

Administration of a high dose of chronic peripheral corticosterone during the postpartum period has been shown to lead to reduced maternal care, but the interference of acute corticosterone, mimicking a situation of acute stress, on maternal behavior has not been well established. Therefore, the aim of our study was to investigate the influence of acute central corticosterone on behavioral and neuroendocrine responses during lactation. On day 7 of lactation, female rats were treated with vehicle (5 μL; i.c.v.) or corticosterone (10 ng/5 μL; i.c.v.) 30 min before the start of the experiment. To evaluate maternal behavior, the pups were returned to the side of their home cages opposite the previous nest, and the resulting behavior of the lactating rats was filmed for the next 30 min. Plasma levels of oxytocin and the amount of milk consumed by the pups were evaluated 15 min after the onset of suckling. In addition, the double-labeled c-Fos/oxytocin neurons in the paraventricular nucleus (PVN) and supraoptic nucleus (SON) and c-Fos immunoreactivity in medial preoptic area (MPOA) neurons were quantified for each lactating rat. Corticosterone decreased maternal care, plasma oxytocin levels, milk consumption by the pups, the activation of oxytocinergic neurons in hypothalamic nuclei, and c-Fos immunoreactivity in MPOA neurons. Our results indicate that changes in the behavioral responses of lactating rats treated with corticosterone may be related to disruption of the neuroendocrine control of oxytocin secretion.

The role of oxytocin in male and female reproductive behavior

Oxytocin (OT) is a nonapeptide with an impressive variety of physiological functions. Among them, the 'prosocial' effects have been discussed in several recent reviews, but the direct effects on male and female sexual behavior did receive much less attention so far. As our contribution to honor the lifelong interest of Berend Olivier in the control mechanisms of sexual behavior, we decided to explore the role of OT in the present review. In the successive sections, some physiological mechanisms and the 'pair-bonding' effects of OT will be discussed, followed by sections about desire, female appetitive and copulatory behavior, including lordosis and orgasm. At the male side, the effects on erection and ejaculation are reviewed, followed by a section about 'premature ejaculation' and a possible role of OT in its treatment. In addition to OT, serotonin receives some attention as one of the main mechanisms controlling the effects of OT. In the succeeding sections, the importance of OT for 'the fruits of labor' is discussed, as it plays an important role in both maternal and paternal behavior. Finally, we pay attention to an intriguing brain area, the ventrolateral part of the ventromedial hypothalamic nucleus (VMHvl), apparently functioning in both sexual and aggressive behavior, which are at first view completely opposite behavioral systems.

Corticosterone synthesis inhibitor metyrapone preserves changes in maternal behavior and neuroendocrine responses during immunological challenge in lactating rats

Lactation is associated with profound behavioral and physiological adaptations in the mother that support reproductive success. These include neuroendocrine adaptation to stress that reduces anxiety-related behavior and emotional responsiveness. However, the way in which endogenous glucocorticoids secreted during immunological challenge influence the neuroendocrine system and behavior of lactating rats is not well understood. To evaluate the effects of glucocorticoids on the neuroendocrine response to suckling, maternal behavior and maternal anxiolysis, lactating female rats were treated with vehicle or metyrapone prior to the administration of a saline solution or a lipopolysaccharide (LPS) solution. LPS treatment reduced oxytocin and prolactin secretion during suckling and affected a variety of maternal behaviors, such as increasing the latency of retrieval a new nest, decreasing the number of pups gathered to the nest, increasing the latency of retrieving the first pup and decreasing the percentage of time spent in the arched-nursing position. In addition, the LPS treatment increased the baseline and avoidance latencies in an elevated T-maze. Pretreatment with metyrapone counteracted effects produced by LPS, including hormonal and behavioral responses in lactating rats. Taken together, our results indicate that stress induced by LPS treatment attenuates the neuroendocrine response to suckling, followed by disruption of maternal behavior and maternal anxiolysis in lactating female rats. These changes may be due to corticosterone release, as evidenced by the reversal of behavioral and neuroendocrine responses after immunological challenge in lactating rats that had been pretreated with metyrapone.