Maternal behavior and developmental psychopathology

Neuronal nitric oxide synthase contributes to chronic stress-induced depression by suppressing hippocampal neurogenesis

Increasing evidence suggests that depression may be associated with a lack of hippocampal neurogenesis. It is well established that neuronal nitric oxide synthase (nNOS)-derived NO exerts a negative control on the hippocampal neurogenesis. Using genetic and pharmacological methods, we investigated the roles of nNOS in depression induced by chronic mild stress (CMS) in mice. Hippocampal nNOS over-expression was first observed 4 days and remained elevated 21 and 56 days after exposure to CMS. The mice exposed to CMS exhibited behavioral changes typical of depression, and impaired neurogenesis in the hippocampus. The CMS-induced behavioral despair and hippocampal neurogenesis impairment were prevented and reversed in the null mutant mice lacking nNOS gene (nNOS-/-) and in the mice receiving nNOS inhibitor. Disrupting hippocampal neurogenesis blocked the antidepressant effect of nNOS inhibition. Moreover, nNOS-/- mice exhibited antidepressant-like properties. Our findings suggest that nNOS over-expression in the hippocampus is essential for chronic stress-induced depression and inhibiting nNOS signaling in brain may represent a novel approach for the treatment of depressive disorders.

Neural circuits underlying crying and cry responding in mammals

Crying is a universal vocalization in human infants, as well as in the infants of other mammals. Little is known about the neural structures underlying cry production, or the circuitry that mediates a caregiver's response to cry sounds. In this review, the specific structures known or suspected to be involved in this circuit are identified, along with neurochemical systems and hormones for which evidence suggests a role in responding to infants and infant cries. In addition, evidence that crying elicits parental responses in different mammals is presented. An argument is made for including 'crying' as a functional category in the vocal repertoire of all mammalian infants (and the adults of some species). The prevailing neural model for crying production considers forebrain structures to be dispensable. However, evidence for the anterior cingulate gyrus in cry production, and this structure along with the amygdala and some other forebrain areas in responding to cries is presented.

ERK-FosB signaling in dorsal MPOA neurons plays a major role in the initiation of parental behavior in mice

During mouse parental behavior, neurons in the dorsal medial preoptic area (MPOAd) are activated and express transcription factors such as c-Fos and FosB. FosB-knockout mice are reported to be defective in parental care. To clarify molecular signaling responsible for parental behavior, we investigated gene expression profiles in the MPOAd of parental versus nonparental mice. We identified upregulation of NGFI-B, SPRY1, and Rad in parental mice, together with c-Fos and FosB. A common inducer of these genes, the extracellular signal regulated kinase (ERK) was phosphorylated in MPOAd neurons upon pup exposure. Pharmacological blockade of ERK phosphorylation inhibited the FosB upregulation in MPOAd, and the initiation of pup retrieving in virgin female mice, but did not affect the established parenting in parous females. Furthermore, induction of SPRY1 and Rad was impaired in MPOAd of nonparental FosB-knockout mice. These results suggest the pivotal role of ERK-FosB signaling in the initiation of parental care.

Maternal postpartum behavior and the emergence of infant–mother and infant–father synchrony in preterm and full-term infants: The role of neonatal vagal tone

Relations between maternal postpartum behavior and the emergence of parent-infant relatedness as a function of infant autonomic maturity were examined in 56 premature infants (birthweight = 1000-1500 g) and 52 full-term infants. Maternal behavior, mother depressive symptoms, and infant cardiac vagal tone were assessed in the neonatal period. Infant-mother and infant-father synchrony, maternal and paternal affectionate touch, and the home environment were observed at 3 months. Premature birth was associated with higher maternal depression, less maternal behaviors, decreased infant alertness, and lower coordination of maternal behavior with infant alertness in the neonatal period. At 3 months, interactions between premature infants with their mothers and fathers were less synchronous. Interaction effects of premature birth and autonomic maturity indicated that preterm infants with low vagal tone received the lowest amounts of maternal behavior in the postpartum and the least maternal touch at 3 months. Infant-mother and infant-father synchrony were each predicted by cardiac vagal tone and maternal postpartum behavior in both the preterm and full-term groups. Among preterm infants, additional predictors of parent-infant synchrony were maternal depression (mother only) and the home environment (mother and father). Findings are consistent with evolutionary perspectives on the higher susceptibility of dysregulated infants to rearing contexts and underscore the compensatory mechanisms required for social-emotional growth under risk conditions for parent-infant bonding.

Brain basis of early parent-infant interactions: psychology, physiology, and in vivo functional neuroimaging studies

Parenting behavior critically shapes human infants' current and future behavior. The parent-infant relationship provides infants with their first social experiences, forming templates of what they can expect from others and how to best meet others' expectations. In this review, we focus on the neurobiology of parenting behavior, including our own functional magnetic resonance imaging (fMRI) brain imaging experiments of parents. We begin with a discussion of background, perspectives and caveats for considering the neurobiology of parent-infant relationships. Then, we discuss aspects of the psychology of parenting that are significantly motivating some of the more basic neuroscience research. Following that, we discuss some of the neurohormones that are important for the regulation of social bonding, and the dysregulation of parenting with cocaine abuse. Then, we review the brain circuitry underlying parenting, proceeding from relevant rodent and nonhuman primate research to human work. Finally, we focus on a study-by-study review of functional neuroimaging studies in humans. Taken together, this research suggests that networks of highly conserved hypothalamic-midbrain-limbic-paralimbic-cortical circuits act in concert to support aspects of parent response to infants, including the emotion, attention, motivation, empathy, decision-making and other thinking that are required to navigate the complexities of parenting. Specifically, infant stimuli activate basal forebrain regions, which regulate brain circuits that handle specific nurturing and caregiving responses and activate the brain's more general circuitry for handling emotions, motivation, attention, and empathy--all of which are crucial for effective parenting. We argue that an integrated understanding of the brain basis of parenting has profound implications for mental health.

From too little too late to early and often: child psychiatry education during medical school (and before and after)

In this article we propose developmentally informed remedies to the challenges that face research training. The initiatives described in it have been implemented to various degrees at our institution, and several are already being replicated or expanded through strategic partnerships across the country. We are fortunate to work in an environment in which child and adolescent psychiatry is visible and well represented, but we are aware than many of the settings in which education and recruitment needs are most pressing may not have the range of our resources. We view our different programs as seamlessly interconnected with one another but present them as separate entities to facilitate the incorporation of different components into local realities.

Prenatal influences on brain dopamine and their relevance to the rising incidence of autism

The incidence of autism has risen 10-fold since the early 1980s, with most of this rise not explainable by changing diagnostic criteria. The rise in autism is paradoxical in that autism is considered to be one of the most genetically determined of the major neurodevelopmental disorders and should accordingly either be stable or even declining. Because a variety of epigenetic influences, particularly those occurring during the prenatal period, can override or masquerade as genetic influences, these should be considered as prime contributors to the recent increase of autism. Prenatal influences on dopamine activity are especially well-documented, including the effects of maternal psychosocial stress, maternal fever, maternal genetic and hormonal status, use of certain medications, urban birth, and fetal hypoxia. All of these factors have been implicated in the genesis of autism, which is characterized by a "hyperdopaminergic" state based on evidence from monkey and human behavioral studies, pharmacological studies in humans, and a left-hemispheric predominance of both dopamine and autistic-like symptoms. Chronically high maternal levels of dopamine caused by the pressures of increasingly urbanized societies and by changing maternal demographics such as increased workforce participation, educational achievement level, and age at first birth, may be especially significant epigenetic contributors to the recent autism rise.

Activation of maternal behavior of albino rats after combined treatment with dopamine and opioid receptor antagonists in low doses

We studied the effect of D1/D2 antagonist haloperidol on maternal motivation in nursing albino rats. Haloperidol in a dose of 0.2 mg/kg significantly attenuated parental reactions and motor and exploratory activities. In a lower dose (0.1 mg/kg) the drug produced the same effect on maternal behavior (number of approaches to newborns) without reducing motor activity. The effect of low-dose haloperidol was different after naloxone treatment (0.2 mg/kg intranasally): the number of pup transfers increased significantly. The detected phenomenon indicates good prospects of combined treatment with agents modifying the cerebral dopaminergic and opioid systems as the method for correction of disorders in maternal behavior.

Prenatal and postnatal maternal contributions in the infection model of schizophrenia

Epidemiological studies have indicated that the risk of schizophrenia is enhanced by prenatal maternal infection with viral or bacterial pathogens. Recent experimentation in rodents has yielded additional support for a causal relationship between prenatal immune challenge and the emergence of psychosis-related abnormalities in brain and behaviour in later life. However, little is known about the putative roles of maternal postnatal factors in triggering and modulating the emergence of psychopathology following prenatal immunological stimulation. Here, we aimed to dissect the relative contributions of prenatal inflammatory events and postnatal maternal factors in precipitating juvenile and adult psychopathology in the resulting offspring with a cross-fostering design. Pregnant mice were exposed to the viral mimic, polyriboinosinic-polyribocytidilic acid (PolyI:C; at 5 mg/kg, intravenously), or vehicle treatment on gestation day 9, and offspring born to PolyI:C- and vehicle-treated dams were then simultaneously cross-fostered to surrogate rearing mothers, which had either experienced inflammatory or vehicle treatment during pregnancy. Prenatal PolyI:C administration did not affect the expression of latent inhibition (LI) at a juvenile stage of development, but led to the post-pubertal emergence of LI disruption in both aversive classical and instrumental conditioning regardless of the postnatal rearing condition. In addition, deficits in conditioning as such led to a pre- and post-pubertal loss of LI in prenatal control animals that were adopted by PolyI:C-treated surrogate mothers. Our findings thus indicate that the adoption of prenatally immune-challenged neonates by control surrogate mothers does not possess any protective effects against the subsequent emergence of psychopathology in adulthood. At the same time, however, the present study highlights for the first time that the adoption of prenatal control animals by immune-challenged rearing mothers is sufficient to precipitate learning disabilities in the juvenile and adult offspring.

Cyclic AMP response element-binding protein is required for normal maternal nurturing behavior

Analysis of mice with targeted disruptions of fosB or the gene encoding dopamine beta-hydroxylase suggests that FosB and adrenergic signaling play critical roles in maternal nurturing behavior. The majority of neonates born to null females from either mutation fail to thrive, and virgin mutant females of both lines exhibit impaired pup retrieval. Considering whether FosB and adrenergic signaling might share a signaling pathway important for maternal behavior, we examined the role of a potential intermediary, cyclic AMP response element-binding protein (CREB). Here we report that approximately 40% of neonates (all heterozygous) born to mice lacking the major isoforms of CREB (Creb-alphaDelta-/-) died within several days of birth. In contrast, heterozygotes born to Creb-alphaDelta+/- females thrived. Cross-fostering demonstrated that neonates born to Creb-alphaDelta(-/dagger/-) females thrived when reared by wild-type females, and that Creb-alphaDelta-/- females were capable of rearing neonates whose maternal care was initiated by wild-type females. Further, virgin Creb-alphaDelta-/- females were deficient in pup retrieval despite exhibiting normal investigation of pups and of novel objects. No maternal behavior phenotype was present in mice with a null mutation of the cyclic AMP response element modulator (Crem) gene. Interestingly, the number of cells immunostaining for phospho-CREB (on Ser(133)) in the medial preoptic area of the hypothalamus, a key region for the expression of maternal behavior, increased nearly three-fold in wild-type mice following exposure to pups but not to novel objects. On the other hand, basal expression and induction of FosB in response to pup exposure appeared to be independent of CREB because levels were equivalent between wild-type and Creb-alphaDelta-/- females. These results implicate CREB in maternal nurturing behavior and suggest that CREB is not critical for expression or induction of FosB in adult virgin female mice.

Inter-individual vs line/strain differences in psychogenetically selected Roman High-(RHA) and Low-(RLA) Avoidance rats: neuroendocrine and behavioural aspects

Inter-individual differences in neuroendocrine and behavioural responses to environmental challenges will be considered within the context of psychogenetic selection, using the Roman High-(RHA) and Low-(RLA) Avoidance rat lines as an example. We assume that the selected genotypes, by interacting with environmental factors, determine specific 'biobehavioural profiles'. Practical and theoretical problems regarding the measurement of inter-individual vs line/strain differences, the definition of 'traits' vs experimental variables, and possible correlations between physiological and behavioural parameters will be discussed. We will argue that environmental influences are the main cause of inter-individual variability, and that the genotype only constitutes a 'blueprint' from which typical biobehavioural profiles are established, notably under the influence of early environmental factors. These biobehavioural profiles may correspond in part to human categories known as 'types', 'temperaments' or 'personality traits'. Within each category (including those which can be obtained by psychogenetic selection), more individual personality traits can evolve, notably as a result of social interactions and particular life events.

Early life genetic, epigenetic and environmental factors shaping emotionality in rodents

Childhood trauma is known to increase risk for emotional disorders and addiction. However, little is currently understood about the neurodevelopmental basis of these effects, or how genetic and epigenetic factors interact with the environment to shape the systems subserving emotionality. In this review, we discuss the use of rodent models of early life emotional experience to study these issues in the laboratory and present some of our pertinent findings. In rats, postnatal maternal separation can produce lasting increases in emotional behavior and stressor-reactivity, together with alterations in various brain neurotransmitter systems implicated in emotionality, including corticotropin-releasing factor, serotonin, norepinephrine, and glutamate. Genetic differences between inbred mouse strains have been exploited to further study how maternal behavior affects emotional development using techniques such as cross-fostering and generation of inter-strain hybrids. Together with our own recent data, the findings of these studies demonstrate the pervasive influence of maternal and social environments during sensitive developmental periods and reveal how genetic factors determine how these early life experiences can shape brain and behavior throughout life.

How the brain processes social information: searching for the social brain

Because information about gender, kin, and social status are essential for reproduction and survival, it seems likely that specialized neural mechanisms have evolved to process social information. This review describes recent studies of four aspects of social information processing: (a) perception of social signals via the vomeronasal system, (b) formation of social memory via long-term filial imprinting and short-term recognition, (c) motivation for parental behavior and pair bonding, and (d) the neural consequences of social experience. Results from these studies and some recent functional imaging studies in human subjects begin to define the circuitry of a "social brain." Such neurodevelopmental disorders as autism and schizophrenia are characterized by abnormal social cognition and corresponding deficits in social behavior; thus social neuroscience offers an important opportunity for translational research with an impact on public health.

Early relationship environments: physiology of skin-to-skin contact for parents and their preterm infants

Skin-to-skin care involves the mother placing her diaper-clad infant upright between her breasts in direct skin contact. The practice has evolved worldwide to be an intervention strategy in neonatal intensive care units for premature infants and their mothers. Few adverse outcomes have been noted in thermoregulation, cardiovascular changes, or behavioral organization. Findings have been positively related to better infant physiologic and neurobehavioral outcomes, maternal breastfeeding success, and positive attachment relationships. The early, intimate, and physiologically stabilizing benefits of skin-to-skin care provide for a new conceptualization of the optimal environment for preterm infants in intensive care.

The genetics of autism

Autism is a complex, behaviorally defined, static disorder of the immature brain that is of great concern to the practicing pediatrician because of an astonishing 556% reported increase in pediatric prevalence between 1991 and 1997, to a prevalence higher than that of spina bifida, cancer, or Down syndrome. This jump is probably attributable to heightened awareness and changing diagnostic criteria rather than to new environmental influences. Autism is not a disease but a syndrome with multiple nongenetic and genetic causes. By autism (the autistic spectrum disorders [ASDs]), we mean the wide spectrum of developmental disorders characterized by impairments in 3 behavioral domains: 1) social interaction; 2) language, communication, and imaginative play; and 3) range of interests and activities. Autism corresponds in this article to pervasive developmental disorder (PDD) of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition and International Classification of Diseases, Tenth Revision. Except for Rett syndrome--attributable in most affected individuals to mutations of the methyl-CpG-binding protein 2 (MeCP2) gene--the other PDD subtypes (autistic disorder, Asperger disorder, disintegrative disorder, and PDD Not Otherwise Specified [PDD-NOS]) are not linked to any particular genetic or nongenetic cause. Review of 2 major textbooks on autism and of papers published between 1961 and 2003 yields convincing evidence for multiple interacting genetic factors as the main causative determinants of autism. Epidemiologic studies indicate that environmental factors such as toxic exposures, teratogens, perinatal insults, and prenatal infections such as rubella and cytomegalovirus account for few cases. These studies fail to confirm that immunizations with the measles-mumps-rubella vaccine are responsible for the surge in autism. Epilepsy, the medical condition most highly associated with autism, has equally complex genetic/nongenetic (but mostly unknown) causes. Autism is frequent in tuberous sclerosis complex and fragile X syndrome, but these 2 disorders account for but a small minority of cases. Currently, diagnosable medical conditions, cytogenetic abnormalities, and single-gene defects (eg, tuberous sclerosis complex, fragile X syndrome, and other rare diseases) together account for <10% of cases. There is convincing evidence that "idiopathic" autism is a heritable disorder. Epidemiologic studies report an ASD prevalence of approximately 3 to 6/1000, with a male to female ratio of 3:1. This skewed ratio remains unexplained: despite the contribution of a few well characterized X-linked disorders, male-to-male transmission in a number of families rules out X-linkage as the prevailing mode of inheritance. The recurrence rate in siblings of affected children is approximately 2% to 8%, much higher than the prevalence rate in the general population but much lower than in single-gene diseases. Twin studies reported 60% concordance for classic autism in monozygotic (MZ) twins versus 0 in dizygotic (DZ) twins, the higher MZ concordance attesting to genetic inheritance as the predominant causative agent. Reevaluation for a broader autistic phenotype that included communication and social disorders increased concordance remarkably from 60% to 92% in MZ twins and from 0% to 10% in DZ pairs. This suggests that interactions between multiple genes cause "idiopathic" autism but that epigenetic factors and exposure to environmental modifiers may contribute to variable expression of autism-related traits. The identity and number of genes involved remain unknown. The wide phenotypic variability of the ASDs likely reflects the interaction of multiple genes within an individual's genome and the existence of distinct genes and gene combinations among those affected. There are 3 main approaches to identifying genetic loci, chromosomal regions likely to contain relevant genes: 1) whole genome screens, searching for linkage of autism to shared genetic markers in populations of multiplex families (families with >1 affected family member; 2) cytogenetic studies that may guide molecular studies by pointing to relevant inherited or de novo chromosomal abnormalities in affected individuals and their families; and 3) evaluation of candidate genes known to affect brain development in these significantly linked regions or, alternatively, linkage of candidate genes selected a priori because of their presumptive contribution to the pathogenesis of autism. Data from whole-genome screens in multiplex families suggest interactions of at least 10 genes in the causation of autism. Thus far, a putative speech and language region at 7q31-q33 seems most strongly linked to autism, with linkages to multiple other loci under investigation. Cytogenetic abnormalities at the 15q11-q13 locus are fairly frequent in people with autism, and a "chromosome 15 phenotype" was described in individuals with chromosome 15 duplications. Among other candidate genes are the FOXP2, RAY1/ST7, IMMP2L, and RELN genes at 7q22-q33 and the GABA(A) receptor subunit and UBE3A genes on chromosome 15q11-q13. Variant alleles of the serotonin transporter gene (5-HTT) on 17q11-q12 are more frequent in individuals with autism than in nonautistic populations. In addition, animal models and linkage data from genome screens implicate the oxytocin receptor at 3p25-p26. Most pediatricians will have 1 or more children with this disorder in their practices. They must diagnose ASD expeditiously because early intervention increases its effectiveness. Children with dysmorphic features, congenital anomalies, mental retardation, or family members with developmental disorders are those most likely to benefit from extensive medical testing and genetic consultation. The yield of testing is much less in high-functioning children with a normal appearance and IQ and moderate social and language impairments. Genetic counseling justifies testing, but until autism genes are identified and their functions are understood, prenatal diagnosis will exist only for the rare cases ascribable to single-gene defects or overt chromosomal abnormalities. Parents who wish to have more children must be told of their increased statistical risk. It is crucial for pediatricians to try to involve families with multiple affected members in formal research projects, as family studies are key to unraveling the causes and pathogenesis of autism. Parents need to understand that they and their affected children are the only available sources for identifying and studying the elusive genes responsible for autism. Future clinically useful insights and potential medications depend on identifying these genes and elucidating the influences of their products on brain development and physiology.

The role of the endocrine system in baboon maternal behavior

BACKGROUND

Human mothers display a wide range of parenting skills, and although we have gathered a large body of evidence on a variety of factors affecting maternal behavior, we still know relatively little about the physiologic correlates of variation in parental behavior in primates.

METHODS

Excreted gonadal and adrenal steroids were measured across parturition in a large sample (n = 89) of group-living female baboons. Maternal behavior data were collected during the first 2 months of infants' life.

RESULTS

We found that changes in the excreted sex steroid hormones and cortisol were associated with baboon mothers' infant-directed behaviors. Mothers who displayed more stress-related behaviors, who were also prone to maintain less contact with their infants, had higher postpartum cortisol levels, higher prepartum pregnanediol-3-glucoronide (PdG) levels, and lower postpartum PdG levels. Mothers with higher prepartum cortisol levels showed higher levels of infant-directed affiliative behaviors.

CONCLUSIONS

These results point toward the importance of the whole endocrine system as a functional unit in terms of enhancing maternal care in primates. The dramatic physiologic changes occurring across parturition may act, in coordination with the cognitive-experiential system, to help the mother cope with the additional challenges imposed by the newborn.

Biopsychosocial issues and risk factors in the family when the child has a chronic illness

Between 10 and 20 million American children and adolescents have some type of chronic health condition or impairment. There has been a recent interest in the psychological aspects--emotional and behavioral--of chronic illness in children and adolescents. Major new areas of science, such as behavioral medicine, have emerged to address the research and clinical demands of this field. Several studies already have demonstrated the increased risk for psychiatric problems in children with chronic health conditions to be three to four times greater than their healthy peers. The proposed perspective shifts from a traditional sole reliance on medical diagnosis to a focus more on the dimensions of adjustment, socioeconomic status, visibility of condition, social support, and family functioning.

Amphetamine effects on prepulse inhibition across-species: replication and parametric extension

Despite the similarities of prepulse inhibition (PPI) of the startle reflex and its apparent neural regulation in rodents and humans, it has been difficult to demonstrate cross-species homology in the sensitivity of PPI to pharmacologic challenges. PPI is disrupted in rats by the indirect dopamine (DA) agonist amphetamine, and while studies in humans have suggested similar effects of amphetamine, these effects have been limited to populations characterized by smoking status and specific personality features. In the context of a study assessing the time course of several DA agonist effects on physiological variables, we failed to detect PPI-disruptive effects of amphetamine in a small group of normal males. The present study was designed to reexamine this issue, using a larger sample and a paradigm that should be more sensitive for detecting drug effects. PPI in rats was shown to be disrupted by the highest dose of amphetamine (3.0 mg/kg) at relatively longer prepulse intervals (>30 ms). In humans, between-subject comparisons of placebo (n=15) vs 20 mg amphetamine (n=15) failed to detect significant PPI-disruptive effects of amphetamine, but significant PPI-disruptive effects at short (10-20 ms) prepulse intervals were detected using within-subject analyses of postdrug PPI levels relative to each subject's baseline PPI. Post hoc comparisons failed to detect greater sensitivity to amphetamine among subjects characterized by different personality and physiological traits. Bioactivity of amphetamine was verified by autonomic and subjective changes. These results provide modest support for cross-species homology in the PPI-disruptive effects of amphetamine, but suggest that these effects in humans at the present dose are subtle and may be best detected using within-subject designs and specific stimulus characteristics.

Seizure-prone EL mice exhibit deficits in pup nursing and retrieval assessed using a novel method of maternal behavior phenotyping

The selectively bred EL mouse strain exhibits hyperreactivity to environmental disturbance reflected by handling-induced seizures and motor hyperactivity in an exploratory task relative to a non-seizure-prone control strain. One possible mechanism for the nongenomic transmission of an adult seizure-prone/hyperactive phenotype is the quality of parenting provided to immature offspring. In particular, the quality of maternal behavior has been implicated as an environmental determinant in rodent biochemical and behavioral development. A complication in testing this hypothesis is that human handling for husbandry and testing itself triggers seizures in seizure-prone EL mice. Thus, the present study evaluated potential EL versus control strain differences in maternal behavior using a novel apparatus for passive observation of undisturbed mice. Nonmaternal behaviors were also measured to control for any nonspecific differences in activity or exploration. EL dams were slower than DDY controls to initiate pup retrieval and spent less time nursing/crouching over pups than DDY mice. EL dams also exhibited a profile of sustained exploration and grooming over time relative to the profile of DDY controls. These results suggest that EL mothers exhibit an overabundance of motor activities that compete with crouching/nursing and retrieval behaviors required for viability of the litter.

The social deficits of the oxytocin knockout mouse

Numerous studies have implicated oxytocin (OT) and oxytocin receptors in the central mediation of social cognition and social behavior. Much of our understanding of OT's central effects depends on pharmacological studies with OT agonists and antagonists. Recently, our knowledge of OT's effects has been extended by the development of oxytocin knockout (OTKO) mice. Mice with a null mutation of the OT gene manifest several interesting cognitive and behavioral changes, only some of which were predicted by pharmacological studies. Contrary to studies in rats, mice do not appear to require OT for normal sexual or maternal behavior, though OT is necessary for the milk ejection reflex during lactation. OTKO pups thrive if raised by a lactating female, but OTKO pups emit fewer ultrasonic vocalizations with maternal separation and OTKO adults are more aggressive than WT mice. Remarkably, OTKO mice fail to recognize familiar conspecifics after repeated social encounters, though olfactory and non-social memory functions appear to be intact. Central OT administration into the amygdala restores social recognition. The development of transgenic mice with specific deficits in social memory represents a promising approach to examine the cellular and neural systems of social cognition. These studies may provide valuable new perspectives on diseases characterized by social deficits, such as autism or reactive attachment disorder.