Brain vasopressin signaling modulates aspects of maternal behavior in lactating rats

Computer vision analysis of mother-infant interaction identified efficient pup retrieval in V1b receptor knockout mice

Close contact between lactating rodent mothers and their infants is essential for effective nursing. Whether the mother's effort to retrieve the infants to their nest requires the vasopressin-signaling via V1b receptor has not been fully defined. To address this question, V1b receptor knockout (V1bKO) and control mice were analyzed in pup retrieval test. Because an exploring mother in a new test cage randomly accessed to multiple infants in changing backgrounds over time, a computer vision-based deep learning analysis was applied to continuously calculate the distances between the mother and the infants as a parameter of their relationship. In an open-field, a virgin female V1bKO mice entered fewer times into the center area and moved shorter distances than wild-type (WT). While this behavioral pattern persisted in V1bKO mother, the pup retrieval test demonstrated that total distances between a V1bKO mother and infants came closer in a shorter time than with a WT mother. Moreover, in the medial preoptic area, parts of the V1b receptor transcripts were detected in galanin- and c-fos-positive neurons following maternal stimulation by infants. This research highlights the effectiveness of deep learning analysis in evaluating the mother-infant relationship and the critical role of V1b receptor in pup retrieval during the early lactation phase.

A vasopressin circuit that modulates mouse social investigation and anxiety-like behavior in a sex-specific manner

One of the largest sex differences in brain neurochemistry is the expression of the neuropeptide arginine vasopressin (AVP) within the vertebrate brain, with males having more AVP cells in the bed nucleus of the stria terminalis (BNST) than females. Despite the long-standing implication of AVP in social and anxiety-like behaviors, the circuitry underlying AVP's control of these behaviors is still not well defined. Using optogenetic approaches, we show that inhibiting AVP BNST cells reduces social investigation in males, but not in females, whereas stimulating these cells increases social investigation in both sexes, but more so in males. These cells may facilitate male social investigation through their projections to the lateral septum (LS), an area with the highest density of sexually differentiated AVP innervation in the brain, as optogenetic stimulation of BNST AVP → LS increased social investigation and anxiety-like behavior in males but not in females; the same stimulation also caused a biphasic response of LS cells ex vivo. Blocking the vasopressin 1a receptor (V1aR) in the LS eliminated all these responses. Together, these findings establish a sexually differentiated role for BNST AVP cells in the control of social investigation and anxiety-like behavior, likely mediated by their projections to the LS.

A vasopressin circuit that modulates sex-specific social interest and anxiety-like behavior in mice

One of the largest sex differences in brain neurochemistry is the male-biased expression of the neuropeptide arginine vasopressin (AVP) within the vertebrate social brain. Despite the long-standing implication of AVP in social and anxiety-like behavior, the precise circuitry and anatomical substrate underlying its control are still poorly understood. By employing optogenetic manipulation of AVP cells within the bed nucleus of the stria terminalis (BNST), we have unveiled a central role for these cells in promoting social investigation, with a more pronounced role in males relative to females. These cells facilitate male social investigation and anxiety-like behavior through their projections to the lateral septum (LS), an area with the highest density of sexually-dimorphic AVP fibers. Blocking the vasopressin 1a receptor (V1aR) in the LS eliminated stimulation-mediated increases in these behaviors. Together, these findings establish a distinct BNST AVP → LS V1aR circuit that modulates sex-specific social interest and anxiety-like behavior.

Enhanced maternal behaviors in a mouse model of congenital blindness

In mammals, mothering is one of the most important prosocial female behavior to promote survival, proper sensorimotor, and emotional development of the offspring. Different intrinsic and extrinsic factors can initiate and maintain these behaviors, such as hormonal, cerebral, and sensory changes. Infant cues also stimulate multisensory systems and orchestrate complex maternal responsiveness. To understand the maternal behavior driven by complex sensory interactions, it is necessary to comprehend the individual sensory systems by taking out other senses. An excellent model for investigating sensory regulation of maternal behavior is a murine model of congenital blindness, the ZRDBA mice, where both an anophthalmic and sighted mice are generated from the same litter. Therefore, this study aims to assess whether visual inputs are essential to driving maternal behaviors in mice. Maternal behaviors were assessed using three behavioral tests, including the pup retrieval test, the home cage maternal behavior test, and the maternal aggression test. Our results show that blind mothers (1) took less time to retrieve their offspring inside the nest, (2) spent more time nursing and licking their offspring in the second- and third-week postpartum, and (3) exhibited faster aggressive behaviors when exposed to an intruder male, compared to the sighted counterparts. This study provides evidence that congenitally blind mothers show more motivation to retrieve the pups, care, and protection towards their pups than sighted ones, likely due to a phenomenon of sensory compensation.

Parental experience is linked with lower vasopressin receptor 1a binding and decreased postpartum androgens in titi monkeys

Parenting induces many neurological and behavioral changes that enable parents to rear offspring. Vasopressin plays an important role in this process via its effects on cognition, affect, and neuroplasticity, and in some cases, via interactions with decreased parental androgens. Thus far, the role of these hormones has been primarily studied in rodents. To address this gap, we explored vasopressin receptors and androgens in titi monkeys, a pair-bonding and biparental primate species. In Studies 1 and 2, we used receptor autoradiography to correlate arginine vasopressin receptor 1a (AVPR1a) binding in the hippocampus (Study 1, n = 10) and the rest of the forebrain (Study 2, n = 23) with parental status, parental experience, parity, infant carrying, and pair affiliation. We found that parents exhibited lower AVPR1a binding than non-parents throughout most brain regions assessed, with especially strong effects in the hippocampus (β = -.61), superior colliculus (β = -.88), lateral septum (β = -.35), and medial preoptic area (β = -.29). The other measures of parental experience also tended to be negatively associated with AVPR1a binding across different brain regions. In Study 3 (n = 44), we compared pre- and postpartum urinary androgen levels in parents and non-parents and found that mothers exhibited a sustained androgen decrease across 3-4 months postpartum (relative to 3 months prepartum; β ranged from -.72 to -.62 for different comparisons). For males, we found that multiparous fathers exhibited decreased androgen levels at 1-2 weeks postpartum (β = -.25) and at 3-4 months postpartum (β = -.40) compared to the prepartum, indicating both immediate and long-term reductions with subsequent paternal experience. Together, the results of this study suggest that decreases in AVPR1a binding and circulating androgens are associated with parental behavior and physiology in titi monkeys.

Electromagnetic-field theories of qualia: can they improve upon standard neuroscience?

How do brains create all our different colors, pains, and other conscious qualities? These various qualia are the most essential aspects of consciousness. Yet standard neuroscience (primarily based on synaptic information processing) has not found the synaptic-firing codes, sometimes described as the "spike code," to account for how these qualia arise and how they unite to form complex perceptions, emotions, et cetera. Nor is it clear how to get from these abstract codes to the qualia we experience. But electromagnetic field (versus synaptic) approaches to how qualia arise have been offered in recent years by Pockett, McFadden, Jones, Bond, Ward and Guevera, Keppler and Shani, Hunt and Schooler, et cetera. These EM-field approaches show promise in offering more viable accounts of qualia. Yet, until now, they have not been evaluated together. We review various EM field theories of qualia, highlight their strengths and weaknesses, and contrast these theories with standard neuroscience approaches.

Poly(I:C)-induced maternal immune activation causes elevated self-grooming in male rat offspring: Involvement of abnormal postpartum static nursing in dam

Introduction: Maternal immune activation (MIA) is closely related to the onset of autism-like behaviors in offspring, but the mechanism remains unclear. Maternal behaviors can influence offspring’s development and behaviors, as indicated in both human and animal studies. We hypothesized that abnormal maternal behaviors in MIA dams might be other factors leading to delayed development and abnormal behaviors in offspring.

Methods: To verify our hypothesis, we analyzed poly(I:C)-induced MIA dam’s postpartum maternal behavior and serum levels of several hormones related to maternal behavior. Pup’s developmental milestones and early social communication were recorded and evaluated in infancy. Other behavioral tests, including three-chamber test, self-grooming test, open field test, novel object recognition test, rotarod test and maximum grip test, were performed in adolescence of pups.

Results: Our results showed that MIA dams exhibit abnormal static nursing behavior but normal basic care and dynamic nursing behavior. The serum levels of testosterone and arginine vasopressin in MIA dams were significantly reduced compared with control dams. The developmental milestones, including pinna detachment, incisor eruption and eye opening, were significantly delayed in MIA offspring compared with control offspring, while the weight and early social communication showed no significant differences between the two groups. Behavioral tests performed in adolescence showed that only male MIA offspring display elevated self-grooming behaviors and reduced maximum grip.

Discussion: In conclusion, MIA dams display abnormal postpartum static nursing behavior concomitantly with reduced serum levels of testosterone and arginine vasopressin, possibly involving in the pathogenesis of delayed development and elevated self-grooming in male offspring. These findings hint that improving dam’s postpartum maternal behavior might be a potential regime to counteract delayed development and elevated self-grooming in male MIA offspring.

Modulation of social behavior by distinct vasopressin sources

The neuropeptide arginine-vasopressin (AVP) is well known for its peripheral effects on blood pressure and antidiuresis. However, AVP also modulates various social and anxiety-related behaviors by its actions in the brain, often sex-specifically, with effects typically being stronger in males than in females. AVP in the nervous system originates from several distinct sources which are, in turn, regulated by different inputs and regulatory factors. Based on both direct and indirect evidence, we can begin to define the specific role of AVP cell populations in social behavior, such as, social recognition, affiliation, pair bonding, parental behavior, mate competition, aggression, and social stress. Sex differences in function may be apparent in both sexually-dimorphic structures as well as ones without prominent structural differences within the hypothalamus. The understanding of how AVP systems are organized and function may ultimately lead to better therapeutic interventions for psychiatric disorders characterized by social deficits.

Oxytocin, Vasopressin, and Social Behavior: From Neural Circuits to Clinical Opportunities

Oxytocin and vasopressin are peptide hormones secreted from the pituitary that are well known for their peripheral endocrine effects on childbirth/nursing and blood pressure/urine concentration, respectively. However, both peptides are also released in the brain, where they modulate several aspects of social behaviors. Oxytocin promotes maternal nurturing and bonding, enhances social reward, and increases the salience of social stimuli. Vasopressin modulates social communication, social investigation, territorial behavior, and aggression, predominantly in males. Both peptides facilitate social memory and pair bonding behaviors in monogamous species. Here we review the latest research delineating the neural circuitry of the brain oxytocin and vasopressin systems and summarize recent investigations into the circuit-based mechanisms modulating social behaviors. We highlight research using modern molecular genetic technologies to map, monitor activity of, or manipulate neuropeptide circuits. Species diversity in oxytocin and vasopressin effects on social behaviors are also discussed. We conclude with a discussion of the translational implications of oxytocin and vasopressin for improving social functioning in disorders with social impairments, such as autism spectrum disorder.

Neuroendocrine regulation of female aggression

Classically the neurobiology of aggression has been studied exclusively in males. Thus, females have been considered mildly aggressive except during lactation. Interestingly, recent studies in rodents and humans have revealed that non-lactating females can show exacerbated and pathological aggression similarly to males. This review provides an overview of recent findings on the neuroendocrine mechanisms regulating aggressive behavior in females. In particular, the focus will be on novel rodent models of exaggerated aggression established in non-lactating females. Among the neuromodulatory systems influencing female aggression, special attention has been given to sex-steroids and sex-steroid-sensitive neuronal populations (i.e., the core nuclei of the neural pathway of aggression) as well as to the neuropeptides oxytocin and vasopressin which are major players in the regulation of social behaviors.

Role of Oxytocin and Vasopressin in Neuropsychiatric Disorders: Therapeutic Potential of Agonists and Antagonists

Oxytocin (OT) and vasopressin (AVP) are hypothalamic neuropeptides classically associated with their regulatory role in reproduction, water homeostasis, and social behaviors. Interestingly, this role has expanded in recent years and has positioned these neuropeptides as therapeutic targets for various neuropsychiatric diseases such as autism, addiction, schizophrenia, depression, and anxiety disorders. Due to the chemical-physical characteristics of these neuropeptides including short half-life, poor blood-brain barrier penetration, promiscuity for AVP and OT receptors (AVP-R, OT-R), novel ligands have been developed in recent decades. This review summarizes the role of OT and AVP in neuropsychiatric conditions, as well as the findings of different OT-R and AVP-R agonists and antagonists, used both at the preclinical and clinical level. Furthermore, we discuss their possible therapeutic potential for central nervous system (CNS) disorders.

Sex-specific parenting and depression evoked by preoptic inhibitory neurons

The role of preoptic GABAergic inhibitory neurons was addressed in parenting, anxiety and depression. Pup exposure and forced swimming resulted in similar c-Fos activation pattern in neurons expressing vesicular GABA transporter in the preoptic area with generally stronger labeling and different distributional pattern in females than in males. Chemogenetic stimulation of preoptic GABAergic cells resulted in elevated maternal motivation and caring behavior in females and mothers but aggression toward pups in males. Behavioral effects were the opposite following inhibition of preoptic GABAergic neurons suggesting their physiological relevance. In addition, increased anxiety-like and depression-like behaviors were found following chemogenetic stimulation of the same neurons in females, whereas previous pup exposure increased only anxiety-like behavior suggesting that not the pups, but overstimulation of the cells can lead to depression-like behavior. A sexually dimorphic projection pattern of preoptic GABAergic neurons was also identified, which could mediate sex-dependent parenting and associated emotional behaviors.

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Preoptic GABAergic neurons promote maternal behaviors in females mice

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Activation of preoptic GABAergic neurons induces pup-directed aggression in males

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Projection pattern of preoptic GABAergic neurons is sexually dimorphic

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Depression-like behaviors are provoked by stimulation of preoptic GABAergic neurons

Hypothalamic Gene Expression and Postpartum Behavior in a Genetic Rat Model of Depression

Postpartum depression is a complex illness that often occurs in genetically predisposed individuals. Closely related inbred rat strains are a great resource to identify novel causative genes and mechanisms underlying complex traits such as postpartum behavior. We report differences in these behaviors between the inbred depression model, Wistar Kyoto (WKY) More Immobile (WMI), and the isogenic control Wistar Kyoto Less Immobile (WLI) dams. WMI dams showed significantly lower litter survival rate and frequency of arched back and blanket nursing, but increased pup-directed licking, grooming, and retrieval during postpartum days (PPD) 1-10, compared to control WLIs. This increased pup-directed behavior and the frequency of self-directed behaviors segregated during selective breeding of the progenitor strain of WKY, which is also a depression model. These behaviors are manifested in the WMIs in contrast to those of WLIs. Furthermore, habitual differences in the self-directed behavior between light and dark cycles present in WLIs were missing in WMI dams. Hypothalamic transcript levels of the circadian rhythm-related gene Lysine Demethylase 5A (Kdm5a), period 2 (Per2), and the maternal behavior-related oxytocin receptor (Oxtr), vasopressin (Avp), and vasopressin receptor 1a (Avpr1a) were significantly greater in the post-weaning WMI dams at PPD 24 compared to those of WLIs, and also to those of WMI dams whose litter died before PPD 5. Expression correlation amongst genes differed in WLI and WMI dams and between the two time-points postpartum, suggesting genetic and litter-survival differences between these strains affect transcript levels. These data demonstrate that the genetically close, but behaviorally disparate WMI and WLI strains would be suitable for investigating the underlying genetic basis of postpartum behavior.

Maternal separation changes maternal care, anxiety-like behaviour and expression of paraventricular oxytocin and corticotrophin-releasing factor immunoreactivity in lactating rats

The early postnatal period is a time of tremendous change for the dam and her offspring. During this time, environmental insults such as repeated stress exposure can have detrimental effects. In research that has focused on the effect of postnatal stress exposure on the dams, conflicting changes in maternal care and anxiety-like behaviour have been reported. Additionally, changes to hypothalamic neuropeptides that are crucially involved in the transition to motherhood and stress regulation, namely oxytocin and corticotrophin-releasing factor (CRF), have not been examined. Accordingly, the present study aimed to determine (i) whether repeated postpartum stress increases engagement in maternal care behaviours and anxiety-like behaviour and (ii) whether these behavioural changes correspond with changes to CRF- or oxytocin-immunoreactive (-IR) cells in the paraventricular nucleus (PVN) of the hypothalamus. A non-lactating group was also included to control for the effects of lactation on anxiety and the hypothalamic neuroendocrine system. Following the birth of their litters, Long-Evans dams were separated from their pups from postnatal day (PND) 1 to PND21 for either 15 minutes (maternal separation [MS]15) or 6 hours (MS360). Maternal behaviours were recorded for 30 minutes on select PNDs following the separation. On PND22, dams were exposed to the elevated plus maze, brains were collected, and immunofluorescence analysis of PVN oxytocin- and CRF-IR cells was conducted. Our findings demonstrate that prolonged maternal separation altered typical maternal behaviours and reduced anxiety relative to MS15 dams. At the cellular level, oxytocin-IR cells in the caudal PVN were reduced in MS360 dams to a level similar to that in non-lactating controls, and PVN CRF-IR cells were reduced relative to both MS15 and non-lactating controls. Taken together, these data reveal the behavioural and neuronal changes that occur in the mother dam following repeated postnatal stress exposure.

More than reproduction: Central gonadotropin-releasing hormone antagonism decreases maternal aggression in lactating rats

Gonadotropin-releasing hormone (GnRH) is a major regulator and activator of the hypothalamic-pituitary-gonadal axis. Many studies have demonstrated the importance of GnRH in reproduction and sexual behaviour. However, to date, only a single study shows an involvement of GnRH in maternal behaviour where a 30% reduction of GnRH neurones abolishes a mother's motivation to retrieve pups. On this basis, we aimed to investigate the effects of acute central GnRH receptor blockade in lactating rats on maternal care under non-stress and stress conditions, maternal motivation in the pup retrieval test, maternal anxiety on the elevated plus maze, and maternal aggression in the maternal defence test. We found that acute central infusion of a GnRH antagonist ([d-Phe^2,6 ,Pro³ ]-luteinising hormone-releasing hormone; 0.5 ng 5 μL^-1 ) impaired a mother's attack behaviour against a female intruder rat during the maternal defence test compared to vehicle controls. However, in contrast to the previous study on reduced GnRH neurones, acute central GnRH antagonism did not affect pup retrieval, nor any other parameter of maternal behaviour or maternal anxiety. Taken together, GnRH receptor activation is mandatory for protection of the offspring. These findings shed new light on GnRH as a neuropeptide acting not exclusively on the reproductive axis but, additionally, on maternal behaviour including pup retrieval and maternal aggression.

Effects of opioids on the parental brain in health and disease

The epidemic of opioid use disorder (OUD) directly affects millions of women of child-bearing age. Unfortunately, parenting behaviors - among the most important processes for human survival - are vulnerable to the effects of OUD. The standard of care for pregnant women with OUD is opioid maintenance therapy (OMT), of which the primary objective is to mitigate addiction-related stress. The aim of this review is to synthesize current information specific to pregnancy and parenting that may be affected by OUD. We first summarize a model of the parental brain supported by animal research and human neuroimaging. We then review animal models of exogenous opioid effects on parental brain and behavior. We also present preliminary data for a unifying hypothesis that may link different effects of exogenous opioids on parenting across species and in the context of OMT. Finally, we discuss future directions that may inform research and clinical decision making for peripartum women with OUD.

Mom doesn't care: When increased brain CRF system activity leads to maternal neglect in rodents

Mothers are the primary caregivers in mammals, ensuring their offspring's survival. This strongly depends on the adequate expression of maternal behavior, which is the result of a concerted action of "pro-maternal" versus "anti-maternal" neuromodulators such as the oxytocin and corticotropin-releasing factor (CRF) systems, respectively. When essential peripartum adaptations fail, the CRF system has negative physiological, emotional and behavioral consequences for both mother and offspring often resulting in maternal neglect. Here, we provide an elaborate and unprecedented review on the implications of the CRF system in the maternal brain. Studies in rodents have advanced our understanding of the specific roles of brain regions such as the limbic bed nucleus of the stria terminalis, medial preoptic area and lateral septum even in a CRF receptor subtype-specific manner. Furthermore, we discuss potential interactions of the CRF system with other neurotransmitters like oxytocin and noradrenaline, and present valuable translational aspects of the recent research.