Mother-pup interactions: rodents and humans

Microbiota-immune-brain interactions: A new vision in the understanding of periodontal health and disease

This review highlights the significance of interactions between the microbiota, immune system, nervous and hormonal systems, and the brain on periodontal health and disease. Microorganisms in the microbiota, immune cells, and neurons communicate via homeostatic nervous and hormonal systems, regulating vital body functions. By modulating pro-inflammatory and anti-inflammatory adaptive immune responses, these systems control the composition and number of microorganisms in the microbiota. The strength of these brain-controlled responses is genetically determined but is sensitive to early childhood stressors, which can permanently alter their responsiveness via epigenetic mechanisms, and to adult stressors, causing temporary changes. Clinical evidence and research with humans and animal models indicate that factors linked to severe periodontitis enhance the responsiveness of these homeostatic systems, leading to persistent hyperactivation. This weakens the immune defense against invasive symbiotic microorganisms (pathobionts) while strengthening the defense against non-invasive symbionts at the gingival margin. The result is an increased gingival tissue load of pathobionts, including Gram-negative bacteria, followed by an excessive innate immune response, which prevents infection but simultaneously destroys gingival and periodontal tissues. Thus, the balance between pro-inflammatory and anti-inflammatory adaptive immunity is crucial in controlling the microbiota, and the responsiveness of brain-controlled homeostatic systems determines periodontal health.

Developmental vitamin D-deficiency produces autism-relevant behaviours and gut-health associated alterations in a rat model

Developmental vitamin D (DVD)-deficiency is an epidemiologically established risk factor for autism. Emerging studies also highlight the involvement of gut microbiome/gut physiology in autism. The current study aims to examine the effect of DVD-deficiency on a broad range of autism-relevant behavioural phenotypes and gut health. Vitamin D deficient rat dams exhibited altered maternal care, DVD-deficient pups showed increased ultrasonic vocalizations and as adolescents, social behaviour impairments and increased repetitive self-grooming behaviour. There were significant impacts of DVD-deficiency on gut health demonstrated by alterations to the microbiome, decreased villi length and increased ileal propionate levels. Overall, our animal model of this epidemiologically validated risk exposure for autism shows an expanded range of autism-related behavioural phenotypes and now alterations in gut microbiome that correlate with social behavioural deficits raising the possibility that DVD-deficiency induced ASD-like behaviours are due to alterations in gut health.

Rodent models of metabolic disorders: considerations for use in studies of neonatal programming

Epidemiologically, metabolic disorders have garnered much attention, perhaps due to the predominance of obesity. The early postnatal life represents a critical period for programming multifactorial metabolic disorders of adult life. Though altricial rodents are prime subjects for investigating neonatal programming, there is still no sufficiently generalised literature on their usage and methodology. This review focuses on establishing five approach-based models of neonatal rodents adopted for studying metabolic phenotypes. Here, some modelled interventions that currently exist to avoid or prevent metabolic disorders are also highlighted. We also bring forth recommendations, guidelines and considerations to aid research on neonatal programming. It is hoped that this provides a background to researchers focused on the aetiology, mechanisms, prevention and treatment of metabolic disorders.

Prefrontal Circuits guiding Social Preference: Implications in Autism Spectrum Disorder

Although Autism Spectrum Disorder (ASD) is increasing in diagnostic prevalence, treatment options are inadequate largely due to limited understanding of ASD's underlying neural mechanisms. Contributing to difficulties in treatment development is the vast heterogeneity of ASD, from physiological causes to clinical presentations. Recent studies suggest that distinct genetic and neurological alterations may converge onto similar underlying neural circuits. Therefore, an improved understanding of neural circuit-level dysfunction in ASD may be a more productive path to developing broader treatments that are effective across a greater spectrum of ASD. Given the social preference behavioral deficits commonly seen in ASD, dysfunction in circuits mediating social preference may contribute to the atypical development of social cognition. We discuss some of the animal models used to study ASD and examine the function and effects of dysregulation of the social preference circuits, notably the medial prefrontal cortex-amygdala and the medial prefrontal cortex-nucleus accumbens circuits, in these animal models. Using the common circuits underlying similar behavioral disruptions of social preference behaviors as an example, we highlight the importance of identifying disruption in convergent circuits to improve the translational success of animal model research for ASD treatment development.

Effects of snack intake during pregnancy and lactation on reproductive outcome in mild hyperglycemic rats

Metabolic disorders, like diabetes, as well as maternal diet, alter nutrient availability in utero, inducing adaptations in the offspring. Whether the effects of maternal hyperglycemia are modulated by diet, however, has yet to be explored. In the current study, we examined this issue by giving females rats, treated neonatally with STZ to induce mild hyperglycemia, and control littermates either ad libitum access to standard chow (Control n = 17; STZ n = 16) or standard chow and snacks (Control-snack n = 18; STZ-snack n = 19) (potato chips and a red fruit-flavored sucrose syrup solution 1.5%) throughout pregnancy and lactation. We hypothesized that the maternal glucose intolerance typically seen in female rats treated neonatally with STZ would be exacerbated by snack intake, and that the combination of snack intake and STZ treatment would lead to alterations in maternal behavior and offspring development. Maternal body weight and food intake were measured daily through pregnancy and lactation and litter weight throughout lactation. At birth, litter size, offspring weight, body length, and anogenital distance were obtained and offspring were classified according to their weight. Measures of nursing and retrieval behavior, as well as exploration in the open field and the elevated plus-maze were also recorded. As predicted, snack intake tended to aggravate the glucose intolerance of STZ-treated rats during pregnancy. Both Control and STZ-treated females that had access to snacks ate more calories and fat, but less carbohydrate and protein than females having access to chow alone. Overall, STZ-treated dams gave birth to fewer pups. Chow-fed STZ females gave birth to a greater proportion of large for pregnancy age pups, whereas dams in the Control-snack group gave birth to a greater proportion of small pups. The birth weight classification of pups born to STZ-snack rats, however, resembled that of the Control chow-fed females. Although all litters gained weight during lactation, litters from snack-fed dams gained less weight regardless of maternal hyperglycemia and did not show catch-up growth by weaning. Overall, STZ rats spent more time nest building, whereas the average inter milk ejection interval was higher in snack-fed females. STZ-snack dams retrieved the complete litter faster than dams in the other groups. Together, these data suggest that when mild hyperglycemic females are given access to snacks throughout pregnancy and lactation their intake is similar to that of Control females given snack access. The combination of hyperglycemia and snack access tended to decrease glucose tolerance in pregnancy, and normalized birth weight classification, but produced few other effects that were not seen as a function of snack intake or hyperglycemia alone. Since birth weight is a strong predictor of health issues, future studies will further investigate offspring behavioral and metabolic outcomes later in life.

Mother brain is wired for social moments

Reorganization of the maternal brain upon childbirth triggers the species-typical maternal social behavior. These brief social moments carry profound effects on the infant's brain and likely have a distinct signature in the maternal brain. Utilizing a double-blind, within-subject oxytocin/placebo administration crossover design, mothers' brain was imaged twice using fMRI while observing three naturalistic maternal-infant contexts in the home ecology; 'unavailable', 'unresponsive', and 'social', when mothers engaged in synchronous peek-a-boo play. The social condition elicited greater neural response across the human caregiving network, including amygdala, VTA, hippocampus, insula, ACC, and temporal cortex. Oxytocin impacted neural response primarily to the social condition and attenuated differences between social and non-social stimuli. Greater temporal consistency emerged in the 'social' condition across the two imaging sessions, particularly in insula, amygdala, and TP. Findings describe how mother's brain varies by caregiving experiences and gives salience to moments of social synchrony that support infant development and brain maturation.

How babies learn: The autonomic socioemotional reflex

BACKGROUND

Human and animal research has long documented the negative effects of early traumatic events on long-term development and socioemotional behavior. Yet, how and where the body stores these memories remains unclear. Current theories propose that the brain stores such memory in the subcortical limbic system. However, a clear theory of change with testable hypothesis has yet to emerge.

AIMS

In this paper, we review the classical Pavlovian conditioning learning tradition, along with its functional variant. Then, we review calming cycle theory, which builds upon the idea that mother/infant learning is distinct from other types of learning, requiring a new set of assumptions in light of functional Pavlovian conditioning.

CONCLUSION

Calming cycle theory states that learning of behaviors associated with subcortical autonomic physiology is separate and distinct from learning of behaviors associated with cortical physiology. Mother/infant autonomic learning starts in the uterine environment via functional Pavlovian co-conditioning that is stored as conditional reflexes within the dyad's autonomic nervous systems. These reflexes are preserved transnatally as autonomic socioemotional reflexes (ASRs), which can be used to monitor mother-infant relational health. The functional Pavlovian co-conditioning mechanism can be exploited to change the physiological/behavioral reflex response. The theory provides a well established learning mechanism, a theory of change and a method of change, along with a set of hypotheses with which to test the theory. We present evidence from a randomized controlled trial with prematurely born infants and their mothers that supports calming cycle theory.

A simple method for short-term maintenance of neonatal mice without foster mothers

Mice are typically weaned from their mother between 21 and 28 days of age, or at 10 grams of body weight. However, some biochemical experiments need to be done before the weaning days, and the mother might cannibalize or ignore those manipulated pups. Here, we provide a detailed protocol for maintenance of neonatal mice without the presence of their mothers for biomedical research. The basic instinct of neonate mice to hide under covers is harnessed for their survival in a mother-free environment. When covers are soaked with milk and the only targets for hiding, the neonates would acquire their nutrients at least in an involuntary fashion. The protocol is simple and can be used for neonatal rodent studies for short periods of times, and assures the accuracy of the biomedical experiments if survival rate of neonates is critical.

Post-weaning infant-to-mother bonding in nutritionally independent female mice

Infant-parent attachment is highly selective and continues beyond essential care in primates, most prominently in humans, and the quality of this attachment crucially determines cognitive and emotional development of the infant. Altricial rodent species such as mice (Mus musculus) display mutual recognition and communal nursing in wild and laboratory environments, but parental bonding beyond the nursing period has not been reported. We presently demonstrated that socially and nutritionally independent mice still prefer to interact selectively with their mother dam. Furthermore, we observed gender differences in the mother-infant relationship, and showed disruption of this relationship in haploinsufficient Nbea+/- mice, a putative autism model with neuroendocrine dysregulation. To our knowledge, this is the first observation of murine infant-to-mother bonding beyond the nursing period.

Interaction between postpartum stage and litter age on maternal caregiving and medial preoptic area orexin

Most maternal caregiving behaviors change across lactation to match the developmental needs of the continuously aging offspring. However, it is mostly unknown whether the dams' postpartum stage or litter age is the primary driving force of these changes. In this study, postnatal day 1 and 8 litters were cross-fostered or in-fostered to postpartum day 1 or 8 dams. Five days later, undisturbed observations of maternal caregiving behaviors were performed on the subsequent two days. We found a main effect of dams' postpartum stage on the frequency that mothers spent with the pups and displayed erect postures over them (hovering over and kyphosis), although it was mostly driven by an interaction between postpartum stage and litter age: early-postpartum dams were in contact with younger litters and in erect postures more often with younger litters compared to later-postpartum dams with younger litters. Additionally, there was an interaction between postpartum stage and litter age on the litter weights because older litters living with later-postpartum dams were heavier than older litters living with early-postpartum dams. There was also an interaction between postpartum stage and litter age on the dams' bodyweight, with early-postpartum dams living with younger litters weighing the least and later-postpartum dams living with younger litters weighing the most. Because activity of the neuropeptide, orexin, within the medial preoptic area (mPOA) has been implicated in maternal nursing and other caregiving behaviors, we measured mPOA levels of orexin-A but it was not affected by postpartum stage or litter age (nor was there an interaction). However, high orexin-A was negatively associated with the frequency of contact with pups and the display of erect postures. These results indicate that changes in caregiving across lactation are driven by endogenous factors in the dams, age-related cues they receive from offspring, and interactions between these factors.

Oxytocin and arginine vasopressin systems in the domestication process

Domestication is of unquestionable importance to the technological revolution that has given rise to modern human societies. In this study, we analyzed the DNA and protein sequences of six genes of the oxytocin and arginine vasopressin systems (OXT-OXTR; AVP-AVPR1a, AVPR1b and AVPR2) in 40 placental mammals. These systems play an important role in the control of physiology and behavior. According to our analyses, neutrality does not explain the pattern of molecular evolution found in some of these genes. We observed specific sites under positive selection in AVPR1b (ω = 1.429, p = 0.001) and AVPR2 (ω= 1.49, p = 0.001), suggesting that they could be involved in behavior and physiological changes, including those related to the domestication process. Furthermore, AVPR1a, which plays a role in social behavior, is under relaxed selective constraint in domesticated species. These results provide new insights into the nature of the domestication process and its impact on the OXT-AVP system.

Oxytocin Neurons Exhibit Extensive Functional Plasticity Due To Offspring Age in Mothers and Fathers

The needs of offspring change as they develop. Thus, parents should concomitantly change their investment based on the age-related needs of the offspring as they mature. Due to the high costs of parental care, it is optimal for parents to exhibit a shift from intense caregiving of young offspring to promoting independence in older offspring. Yet, the neural mechanisms that underlie shifts in parental behavior are poorly understood, and little is known about how the parental brain responds to offspring of different ages. To elucidate mechanisms that relate to shifts in parental behavior as offspring develop, we examined behavioral and neural responses of male and female prairie voles (Microtus ochrogaster), a biparental rodent, to interactions with offspring at different stages of development (ranging from neonatal to weaning age). Importantly, in biparental species, males and females may adjust their behavior differentially as offspring develop. Because the nonapeptides, vasopressin (VP) and oxytocin (OT), are well known for modulating aspects of parental care, we focused on functional activity of distinct VP and OT cell groups within the maternal and paternal brain in response to separation from, reunion (after a brief period of separation) with, or no separation from offspring of different ages. We found several differences in the neural responses of individual VP and OT cell groups that varied based on the age of pups and sex of the parent. Hypothalamic VP neurons exhibit similar functional responses in both mothers and fathers. However, hypothalamic and amygdalar OT neurons exhibit differential functional responses to being separated from pups based on the sex of the parent. Our results also reveal that the developmental stage of offspring significantly impacts neural function within OT, but not VP, cell groups of both mothers and fathers. These findings provide insight into the functional plastic capabilities of the nonapeptide system, specifically in relation to parental behavior. Identifying neural mechanisms that exhibit functional plasticity can elucidate one way in which animals are able to shift behavior on relatively short timescales in order to exhibit the most context-appropriate and adaptive behaviors.

Few long-term consequences after prolonged maternal separation in female Wistar rats

Environmental factors during the early-life period are known to have long-term consequences for the adult phenotype. An intimate interplay between genes and environment shape the individual and may affect vulnerability for psychopathology in a sex-dependent manner. A rodent maternal separation model was here used to study the long-term effects of different early-life rearing conditions on adult behavior, HPA axis activity and long-term voluntary alcohol intake in female rats. Litters were subjected to 15 min (MS15) or 360 min (MS360) of daily maternal separation during postnatal day 1–21. In adulthood, the behavioral profiles were investigated using the multivariate concentric square field™ (MCSF) test or examined for HPA axis reactivity by cat-odor exposure with subsequent characterization of voluntary alcohol intake and associated changes in HPA axis activity. Adult female MS360 offspring showed mostly no, or only minor, effects on behavior, HPA axis reactivity and long-term alcohol intake relative to MS15. Instead, more pronounced effects were found dependent on changes in the natural hormonal cycle or by the choice of animal supplier. However, changes were revealed in corticosterone load after long-term alcohol access, as females subjected to MS360 had higher concentrations of fecal corticosterone. The present findings are in line with and expand on previous studies on the long-term effects of maternal separation in female rats with regard to behavior, HPA axis activity and voluntary alcohol intake. It can also be a window into further studies detailing how early-life experiences interact with other risk and protective factors to impact the adult phenotype and how possible sex differences play a role.

Update on Mental Health of Infants and Children of Parents Affected With Mental Health Issues

This paper highlights the most recent publications, in the field of psychiatry, on offspring of patients with psychiatric illnesses such as schizophrenia and bipolar disorder, and then summarizes what we know about the progeny of adults with mood disorders, the most prevalent of parental disorders. Studies examining personality disorders and contextual factors such as stress and trauma are examined with a focus on the crucial question of development and attachment status in children. Findings converge to reveal that offspring of parents (generally mothers) with most major psychiatric disorders present a higher risk for all mental disorders, and a wide range of disorders are also found in children, adolescent, and finally adult offspring of mothers with mood and anxiety disorders. Developmental psychopathology and infant and child psychiatry have focused on early relationship formation through social interaction and attachment patterns as pathways affected by vulnerability or resilience factors. First year of life longitudinal studies following mothers and infants has shown that maternal psychopathology is positively correlated with higher risk of attachment issues. It would seem that pathology appears when adaptation to real-life contexts becomes difficult in association with an accumulation of negative individual characteristics and environmental circumstances. We suggest that in order to move forward psychiatry should embrace a developmental cascade model, which posits a cumulative pathway for the emergence of psychopathology in the developing child. We propose that we have sufficient knowledge today to start implementing multilevel approaches to enhance the health and mental health of the next generation.

Altered corticosterone levels and social play behavior after prolonged maternal separation in adolescent male but not female Wistar rats

Early-life socio-environmental factors are crucial for normal developmental processes; adverse experiences early in life can therefore lead to detrimental effects in several physiological systems. The aim of this study was to examine short-term effects of early adverse experiences in a maternal separation (MS) rodent model. In this study two separation conditions were used: daily 15- (MS15) or 360-min (MS360) separation of the litter from the dam during postnatal day 1-21. In early adolescence, male and female offspring were subjected to a single-isolation procedure with analysis of corticosterone levels prior to and after isolation. In addition, social play behavior was assessed during mid-adolescence. There was a clear difference between male and female offspring in both tests performed. There was no difference in corticosterone levels between the female MS groups, whereas MS360 males showed higher baseline and recovery corticosterone levels than MS15 males. The amount of pinning, a specific social play behavior, was affected by rearing with MS360 males having a higher frequency than MS15 males, while there was no difference between the female MS groups. The observation that males but not females are affected by MS360 has previously been reported for adult animals, and herein we show that this difference is present already in adolescence. Changes in corticosterone levels and social behavior following early-life adversity have been associated with adult behavioral alterations, and our results confirm that these changes emerge already within adolescence.

Neurogenetic and epigenetic correlates of adolescent predisposition to and risk for addictive behaviors as a function of prefrontal cortex dysregulation

As addiction professionals, we are becoming increasingly concerned about preteenagers and young adults' involvement with substance abuse as a way of relieving stress and anger. The turbulent underdeveloped central nervous system, especially in the prefrontal cortex (PFC), provides impetus to not only continue important neuroimaging studies in both human and animal models, but also to encourage preventive measures and cautions embraced by governmental and social media outlets. It is well known that before people reach their 20s, PFC development is undergoing significant changes and, as such, hijacks appropriate decision making in this population. We are further proposing that early genetic testing for addiction risk alleles will offer important information that could potentially be utilized by their parents and caregivers prior to use of psychoactive drugs by these youth. Understandably, family history, parenting styles, and attachment may be modified by various reward genes, including the known bonding substances oxytocin/vasopressin, which effect dopaminergic function. Well-characterized neuroimaging studies continue to reflect region-specific differential responses to drugs and food (including other non-substance-addictive behaviors) via either "surfeit" or "deficit." With this in mind, we hereby propose a "reward deficiency solution system" that combines early genetic risk diagnosis, medical monitoring, and nutrigenomic dopamine agonist modalities to combat this significant global dilemma that is preventing our youth from leading normal productive lives, which will in turn make them happier.