Social approach behaviors in oxytocin knockout mice: comparison of two independent lines tested in different laboratory environments

Low sympathetic tone and obese phenotype in oxytocin-deficient mice

Oxytocin (Oxt) is secreted both peripherally and centrally and is involved in several functions including parturition, milk let-down reflex, social behavior, and food intake. Recently, it has been shown that mice deficient in Oxt receptor develop late-onset obesity. In this study, we characterized a murin model deficient in Oxt peptide (Oxt(-/-)) to evaluate food intake and body weight, glucose tolerance and insulin tolerance, leptin and adrenaline levels. We found that Oxt(-/-) mice develop late-onset obesity and hyperleptinemia without any alterations in food intake in addition to having a decreased insulin sensitivity and glucose intolerance. The lack of Oxt in our murin model also results in lower adrenalin levels which led us to hypothesize that the metabolic changes observed are associated with a decreased sympathetic nervous tone. It has been shown that Oxt neurons in the paraventricular nucleus (PVN) are a component of a leptin-sensitive signaling circuit between the hypothalamus and caudal brain stem for the regulation of food intake and energy homeostasis. Nevertheless, the lack of Oxt in these mice does not have a direct impact on feeding behavior whose regulation is probably dependent on the complex interplay of several factors. The lack of hyperphagia evident in the Oxt(-/-) mice may, in part, be attributed to the developmental compensation of other satiety factors such as cholecystokinin or bombesin-related peptides which merits further investigation. These findings identify Oxt as an important central regulator of energy homeostasis.

Oxytocin: the great facilitator of life

Oxytocin (Oxt) is a nonapeptide hormone best known for its role in lactation and parturition. Since 1906 when its uterine-contracting properties were described until 50 years later when its sequence was elucidated, research has focused on its peripheral roles in reproduction. Only over the past several decades have researchers focused on what functions Oxt might have in the brain, the subject of this review. Immunohistochemical studies revealed that magnocellular neurons of the hypothalamic paraventricular and supraoptic nuclei are the neurons of origin for the Oxt released from the posterior pituitary. Smaller cells in various parts of the brain, as well as release from magnocellular dendrites, provide the Oxt responsible for modulating various behaviors at its only identified receptor. Although Oxt is implicated in a variety of "non-social" behaviors, such as learning, anxiety, feeding and pain perception, it is Oxt's roles in various social behaviors that have come to the fore recently. Oxt is important for social memory and attachment, sexual and maternal behavior, and aggression. Recent work implicates Oxt in human bonding and trust as well. Human disorders characterized by aberrant social interactions, such as autism and schizophrenia, may also involve Oxt expression. Many, if not most, of Oxt's functions, from social interactions (affiliation, aggression) and sexual behavior to eventual parturition, lactation and maternal behavior, may be viewed as specifically facilitating species propagation.

Haploinsufficiency for Pten and Serotonin transporter cooperatively influences brain size and social behavior

Autism spectrum disorder (ASD) is a heterogeneous group of neurodevelopmental disorders that share deficits in sociability, communication, and restrictive and repetitive interests. ASD is likely polygenic in origin in most cases, but we presently lack an understanding of the relationships between ASD susceptibility genes and the neurobiological and behavioral phenotypes of ASD. Two genes that have been implicated as conferring susceptibility to ASD are PTEN and Serotonin transporter (SLC6A4). The PI3K and serotonin pathways, in which these genes respectively act, are both potential biomarkers for ASD diagnosis and treatment. Biochemical evidence exists for an interaction between these pathways; however, the relevance of this for the pathogenesis of ASD is unclear. We find that Pten haploinsufficient (Pten(+/-)) mice are macrocephalic, and this phenotype is exacerbated in Pten(+/-); Slc6a4(+/-) mice. Furthermore, female Pten(+/-) mice are impaired in social approach behavior, a phenotype that is exacerbated in female Pten(+/-); Slc6a4(+/-) mice. While increased brain size correlates with decreased sociability across these genotypes in females, within each genotype increased brain size correlates with increased sociability, suggesting that epigenetic influences interact with genetic factors in influencing the phenotype. These findings provide insight into an interaction between two ASD candidate genes during brain development and point toward the use of compound mutant mice to validate biomarkers for ASD against biological and behavioral phenotypes.

Estradiol or diarylpropionitrile decrease anxiety-like behavior of wildtype, but not estrogen receptor beta knockout, mice

Clinical and basic studies demonstrate that estrogen (E-sub-2)-based therapies influence anxiety and mood, but the receptor targets (e.g., a or ss isoform of the estrogen receptor, ER) for these effects requires further investigation. To address the specificity of E2's anxiolytic-like effects through ERss, anxiety, motor, and nociceptive behavior of ovariectomized, wildtype (WT), and ERss knockout (ssERKO) mice was examined. Mice were administered oil vehicle or ER agonists, 17ss-E2 (E2; 0.1 mg/kg; similar affinity for ERa and ERss), and a selective ER modulator, diarylpropionitrile (DPN; 0.1 mg/kg; greater affinity for ERss than ERa). Performance of mice in anxiety (open field, elevated plus maze, elevated zero maze, social interaction), motor activity (activity monitor) and nociception (tailflick, pawlick) measures was compared. Results supported our hypothesis that ERss is important in modulation of anxiety-like behavior by E2 in some tasks. Administration of E2 or DPN to WT, but not ssERKO, mice increased open field central entries, plus maze open arm time, zero maze open quadrant time, and social interaction. This pattern was neither seen in motor activity nor pain threshold measures. Thus, actions of ERss may be important for modulating anxiety-like behavior of mice.

Criteria for validating mouse models of psychiatric diseases

Animal models of human diseases are in widespread use for biomedical research. Mouse models with a mutation in a single gene or multiple genes are excellent research tools for understanding the role of a specific gene in the etiology of a human genetic disease. Ideally, the mouse phenotypes will recapitulate the human phenotypes exactly. However, exact matches are rare, particularly in mouse models of neuropsychiatric disorders. This article summarizes the current strategies for optimizing the validity of a mouse model of a human brain dysfunction. We address the common question raised by molecular geneticists and clinical researchers in psychiatry, "what is a 'good enough' mouse model"?

Light phase testing of social behaviors: not a problem

The rich repertoire of mouse social behaviors makes it possible to use mouse models to study neurodevelopmental disorders characterized by social deficits. The fact that mice are naturally nocturnal animals raises a critical question of whether behavioral experiments should be strictly conducted in the dark phase and whether light phase testing is a major methodologically mistake. Although mouse social tasks have been performed in both phases in different laboratories, there seems to be no general consensus on whether testing phase is a critical factor or not. A recent study from our group showed remarkably similar social scores obtained from inbred mice tested in the light and the dark phase, providing evidence that light phase testing could yield reliable results as robust as dark phase testing for the sociability test. Here we offer a comprehensive review on mouse social behaviors measured in light and dark phases and explain why it is reasonable to test laboratory mice in experimental social tasks in the light phase.

Olfactory cues are sufficient to elicit social approach behaviors but not social transmission of food preference in C57BL/6J mice

Mouse models for the study of autistic-like behaviors are increasingly needed to test hypotheses about the causes of autism, and to evaluate potential treatments. Both the automated three-chambered social approach test and social transmission of food preference have been proposed as mouse behavioral assays with face validity to diagnostic symptoms of autism, including aberrant reciprocal social interactions and impaired communication. Both assays measure aspects of normal social behavior in the mouse. However, little is known regarding the salient cues present in each assay that elicit normal social approach and communication. To deconstruct the critical components, we focused on delivering discrete social and non-social olfactory and visual cues within the context of each assay. Results indicate that social olfactory cues were sufficient to elicit normal sociability in the three-chambered social approach test. On social transmission of food preference, isolated social olfactory cues were sufficient to induce social investigation, but not sufficient to induce food preference. These findings indicate that olfactory cues are important in mouse social interaction, but that additional sensory cues are necessary in certain situations. The present evidence that both the three-chambered social approach assay and the social transmission of food preference assay require socially relevant cues to elicit normal behavior supports the use of these two assays to investigate autism-related behavioral phenotypes in mice.

Androgens with activity at estrogen receptor beta have anxiolytic and cognitive-enhancing effects in male rats and mice

Testosterone (T) and its metabolites may underlie some beneficial effects for anxiety and cognition, but the mechanisms for these effects are unclear. T is reduced to dihydrotestosterone (DHT), which can be converted to 5alpha-androstane,3alpha,17beta-diol (3alpha-diol) and/or 5alpha-androstane-3beta,17beta-diol (3beta-diol). Additionally, T can be converted to androstenedione, and then to androsterone. These metabolites bind with varying affinity to androgen receptors (ARs; T and DHT), estrogen receptors (ERbeta; 3alpha-diol, 3beta-diol), or GABA(A)/benzodiazepine receptors (GBRs; 3alpha-diol, androsterone). Three experiments were performed to investigate the hypothesis that reduced anxiety-like and enhanced cognitive performance may be due in part to actions of T metabolites at ERbeta. Experiment 1: Gonadectomized (GDX) wildtype and ERbeta knockout mice (betaERKO) were subcutaneously (SC) administered 3alpha-diol, 3beta-diol, androsterone, or oil vehicle at weekly intervals, and tested in anxiety tasks (open field, elevated plus maze, light-dark transition) or for cognitive performance in the object recognition task. Experiment 2: GDX rats were administered SC 3alpha-diol, 3beta-diol, androsterone, or oil vehicle, and tested in the same tasks. Experiment 3: GDX rats were androsterone- or vehicle-primed and administered an antagonist of ARs (flutamide), ERs (tamoxifen), or GBRs (flumazenil), or vehicle and then tested in the elevated plus maze. Both rats and wildtype mice, but not betaERKO mice, consistently had reduced anxiety and improved performance in the object recognition task. Androsterone was only effective at reducing anxiety-like behavior in the elevated plus maze and this effect was modestly reduced by flumazenil administration. Thus, actions at ERbeta may be required for T's anxiety-reducing and cognitive-enhancing effects.

Social approach behaviors are similar on conventional versus reverse lighting cycles, and in replications across cohorts, in BTBR T+ tf/J, C57BL/6J, and vasopressin receptor 1B mutant mice

Mice are a nocturnal species, whose social behaviors occur primarily during the dark phase of the circadian cycle. However, laboratory rodents are frequently tested during their light phase, for practical reasons. We investigated the question of whether light phase testing presents a methodological pitfall for investigating mouse social approach behaviors. Three lines of mice were systematically compared. One cohort of each line was raised in a conventional lighting schedule and tested during the light phase, under white light illumination; another cohort was raised in a reverse lighting schedule and tested during their dark phase, under dim red light. Male C57BL/6J (B6) displayed high levels of sociability in our three-chambered automated social approach task when tested in either phase. BTBR T+ tf/J (BTBR) displayed low levels of sociability in either phase. Five cohorts of vasopressin receptor subtype 1b (Avpr1b) null mutants, heterozygotes, and wildtype littermate controls were tested in the same social approach paradigm: three in the dark phase and two in the light phase. All three genotypes displayed normal sociability in four out of the five replications. In the juvenile play test, testing phase had no effect on play soliciting behaviors in Avpr1b mice, but had modest effects on nose sniff and huddling. Taken together, these findings indicate that testing phase is not a crucial factor for studying some forms of social approach in juvenile and adult mice.

From ultrasocial to antisocial: a role for oxytocin in the acute reinforcing effects and long-term adverse consequences of drug use?

Addictive drugs can profoundly affect social behaviour both acutely and in the long-term. Effects range from the artificial sociability imbued by various intoxicating agents to the depressed and socially withdrawn state frequently observed in chronic drug users. Understanding such effects is of great potential significance in addiction neurobiology. In this review we focus on the 'social neuropeptide' oxytocin and its possible role in acute and long-term effects of commonly used drugs. Oxytocin regulates social affiliation and social recognition in many species and modulates anxiety, mood and aggression. Recent evidence suggests that popular party drugs such as MDMA and gamma-hydroxybutyrate (GHB) may preferentially activate brain oxytocin systems to produce their characteristic prosocial and prosexual effects. Oxytocin interacts with the mesolimbic dopamine system to facilitate sexual and social behaviour, and this oxytocin-dopamine interaction may also influence the acquisition and expression of drug-seeking behaviour. An increasing body of evidence from animal models suggests that even brief exposure to drugs such as MDMA, cannabinoids, methamphetamine and phencyclidine can cause long lasting deficits in social behaviour. We discuss preliminary evidence that these adverse effects may reflect long-term neuroadaptations in brain oxytocin systems. Laboratory studies and preliminary clinical studies also indicate that raising brain oxytocin levels may ameliorate acute drug withdrawal symptoms. It is concluded that oxytocin may play an important, yet largely unexplored, role in drug addiction. Greater understanding of this role may ultimately lead to novel therapeutics for addiction that can improve mood and facilitate the recovery of persons with drug use disorders.

Deficits in social behavior and reversal learning are more prevalent in male offspring of VIP deficient female mice

Blockage of vasoactive intestinal peptide (VIP) receptors during early embryogenesis in the mouse has been shown to result in developmental delays in neonates, and social behavior deficits selectively in adult male offspring. Offspring of VIP deficient mothers (VIP +/-) also exhibited developmental delays, and reductions in maternal affiliation and play behavior. In the current study, comparisons among the offspring of VIP deficient mothers (VIP +/-) mated to VIP +/- males with the offspring of wild type (WT) mothers mated to VIP +/- males allowed assessment of the contributions of both maternal and offspring VIP genotype to general health measures, social behavior, fear conditioning, and spatial learning and memory in the water maze. These comparisons revealed few differences in general health among offspring of WT and VIP deficient mothers, and all offspring exhibited normal responses in fear conditioning and in the acquisition phase of spatial discrimination in the water maze. WT mothers produced offspring that were normal in all tests; the reduced VIP in their VIP +/- offspring apparently did not contribute to any defects in the measures under study. However, regardless of their own VIP genotype, all male offspring of VIP deficient mothers exhibited severe deficits in social approach behavior and reversal learning. The deficits in these behaviors in the female offspring of VIP deficient mothers were less severe than in their male littermates, and the extent of their impairment was related to their own VIP genotype. This study has shown that intrauterine conditions had a greater influence on behavioral outcome than did genetic inheritance. In addition, the greater prevalence of deficits in social behavior and the resistance to change seen in reversal learning in the male offspring of VIP deficient mothers indicate a potential usefulness of the VIP knockout mouse in furthering the understanding of neurodevelopmental disorders such as autism.

Behavioral phenotyping strategies for mutant mice

Comprehensive behavioral analyses of transgenic and knockout mice have successfully identified the functional roles of many genes in the brain. Over the past 10 years, strategies for mouse behavioral phenotyping have evolved to maximize the scope and replicability of findings from a cohort of mutant mice, minimize the interpretation of procedural artifacts, and provide robust translational tools to test hypotheses and develop treatments. This Primer addresses experimental design issues and offers examples of high-throughput batteries, learning and memory tasks, and anxiety-related tests.

Estradiol or diarylpropionitrile administration to wild type, but not estrogen receptor beta knockout, mice enhances performance in the object recognition and object placement tasks

Cognitive processes mediated by the hippocampus and cortex are influenced by estradiol (E(2)); however, the mechanisms by which E(2) has these effects are not entirely clear. As such, studies were conducted to begin to address the role of actions at the beta form of the intracellular estrogen receptor (ERbeta) for E(2)'s cognitive effects in adult female mice. We investigated whether E(2) improved performance of wild type (WT) and ERbeta knockout (betaERKO) mice in tasks considered to be mediated by the cortex and hippocampus, the object recognition and object placement tasks. WT and betaERKO mice were ovariectomized (ovx) and E(2) (0.1 mg/kg), an ERbeta selective ER modulator (SERM), diarylpropionitrile (DPN; 0.1 mg/kg), or oil vehicle was administered to mice following training in these tasks. We hypothesized that if E(2) has mnemonic effects, in part, due to its actions at ERbeta, then WT mice administered E(2) or DPN would have improved performance compared to vehicle WT controls, which would not be different from betaERKO mice administered vehicle, E(2) or DPN. Alternatively, activation of ERalpha (with E(2), which is a ligand for both ERalpha and ERbeta) may produce opposing effects on cognition and/or the activation of ERalpha and ERbeta vs. either receptor isoform alone may produce a different pattern of effects. Results obtained supported the hypothesis that ERbeta activation is important for mnemonic effects. Ovx WT, but not betaERKO, mice administered E(2) or DPN had a greater percentage of time exploring a novel object in the object recognition task and a displaced object in the object placement task. Thus, actions at ERbeta may be important for E(2) or SERMs to enhance cognitive performance of female mice in the object recognition and placement tasks.

Autism-like behavioral phenotypes in BTBR T+tf/J mice

Autism is a behaviorally defined neurodevelopmental disorder of unknown etiology. Mouse models with face validity to the core symptoms offer an experimental approach to test hypotheses about the causes of autism and translational tools to evaluate potential treatments. We discovered that the inbred mouse strain BTBR T+tf/J (BTBR) incorporates multiple behavioral phenotypes relevant to all three diagnostic symptoms of autism. BTBR displayed selectively reduced social approach, low reciprocal social interactions and impaired juvenile play, as compared with C57BL/6J (B6) controls. Impaired social transmission of food preference in BTBR suggests communication deficits. Repetitive behaviors appeared as high levels of self-grooming by juvenile and adult BTBR mice. Comprehensive analyses of procedural abilities confirmed that social recognition and olfactory abilities were normal in BTBR, with no evidence for high anxiety-like traits or motor impairments, supporting an interpretation of highly specific social deficits. Database comparisons between BTBR and B6 on 124 putative autism candidate genes showed several interesting single nucleotide polymorphisms (SNPs) in the BTBR genetic background, including a nonsynonymous coding region polymorphism in Kmo. The Kmo gene encodes kynurenine 3-hydroxylase, an enzyme-regulating metabolism of kynurenic acid, a glutamate antagonist with neuroprotective actions. Sequencing confirmed this coding SNP in Kmo, supporting further investigation into the contribution of this polymorphism to autism-like behavioral phenotypes. Robust and selective social deficits, repetitive self-grooming, genetic stability and commercial availability of the BTBR inbred strain encourage its use as a research tool to search for background genes relevant to the etiology of autism, and to explore therapeutics to treat the core symptoms.

Effects of progesterone administration and APPswe+PSEN1Deltae9 mutation for cognitive performance of mid-aged mice

Progesterone (P(4)) and its metabolite, 5alpha-pregnan-3alpha-ol-20-one (3alpha,5alpha-THP) have trophic effects and may improve cognitive function. We investigated the role of progestins in a murine model of Alzheimer's Disease (AD) in which transgenic mice co-overexpress a mutant form of amyloid precursor protein (APPswe) and a deletion in presenilin 1 Delta exon 9 (APPswe+PSEN1Deltae9). We hypothesized that: (1) mice with the APPswe+PSEN1Deltae9 mutation would have performance deficits compared to wildtype mice and (2) long-term administration of P(4) would enhance cognitive performance and increase brain progestin levels over placebo. Mice were ovariectomized at 6 months of age and administered placebo or P(4) via subcutaneously implanted pellets. Mice were tested between 9 and 12 months of age for cognitive performance in the object placement, water maze, object recognition, and T-maze tasks and for motor behavior in an activity monitor and then tissues were collected for steroid measurement. P(4) administration increased progestin levels in cortex, diencephalon, midbrain, and cerebellum of wildtype and mutant mice, but increases in 3alpha,5alpha-THP levels in the hippocampus of APPswe+PSEN1Deltae9 mutant mice were attenuated compared to that observed in wildtype mice. APPswe+PSEN1Deltae9 mice showed poorer performance in hippocampus measures (object placement and water maze tasks). In the object recognition and T-maze task, which are mediated by the cortex and hippocampus, P(4) administration improved performance in both wildtype and APPswe+PSEN1Deltae9 mutant mice compared to placebo administration. Thus, APPswe+PSEN1Delta9 mice have deficits in hippocampal performance and capacity to form 3alpha,5alpha-THP in the hippocampus and both wildtype and APPswe+PSEN1Delta9 mice show beneficial effects of P(4) in cortical function and similar capacity to form 3alpha,5alpha-THP in the cortex.

Mouse behavioral assays relevant to the symptoms of autism

While the cause of autism remains unknown, the high concordance between monozygotic twins supports a strong genetic component. The importance of genetic factors in autism encourages the development of mutant mouse models, to advance our understanding of biological mechanisms underlying autistic behaviors. Mouse models of human neuropsychiatric diseases are designed to optimize (i) face validity (resemblance to the human symptoms) (ii) construct validity (similarity to the underlying causes of the disease) and (iii) predictive validity (expected responses to treatments that are effective in the human disease). There is a growing need for mouse behavioral tasks with all three types of validity, to define robust phenotypes in mouse models of autism. Ideal mouse models will incorporate analogies to the three diagnostic symptoms of autism: abnormal social interactions, deficits in communication and high levels of repetitive behaviors. Social approach is tested in an automated three chambered apparatus that offers the subject a choice between spending time with another mouse, with a novel object, or remaining in an empty familiar environment. Reciprocal social interaction is scored from videotapes of interactions between pairs of unfamiliar mice. Communication is evaluated by measuring emission and responses to vocalizations and olfactory cues. Repetitive behaviors are scored for measures of grooming, jumping, or stereotyped sniffing of one location or object. Insistence on sameness is modeled by scoring a change in habit, for example, reversal of the spatial location of a reinforcer in the Morris water maze or T-maze. Associated features of autism, for example, mouse phenotypes relevant to anxiety, seizures, sleep disturbances and sensory hypersensitivity, may be useful to include in a mouse model that meets some of the core diagnostic criteria. Applications of these assays include (i) behavioral phenotyping of transgenic and knockout mice with mutations in genes relevant to autism; (ii) characterization of inbred strains of mice; (iii) evaluation of environmental toxins; (iv) comparison of behavioral phenotypes with genetic factors, such as unusual expression patterns of genes or unusual single nucleotide polymorphisms; and (v) evaluation of proposed therapeutics for the treatment of autism.

Social deficits in BTBR T+tf/J mice are unchanged by cross-fostering with C57BL/6J mothers

Inbred strains of mice are useful model systems for studying the interactions of genetic and environmental contributions during neurodevelopmental stages. We recently reported an inbred strain, BTBR T+tf/J (BTBR), which, as compared to the commonly used C57BL/6J (B6) strain, displays lower social interactions as juveniles, lower social approach in adult ages, and higher levels of repetitive self-grooming throughout developmental stages. The present study investigated whether the early postnatal maternal environment contributes substantially to the unusually low expression of social behaviors and high self-grooming in BTBR as compared to B6. Within 24h of birth, entire litters of pups were cross-fostered to either a dam of the same strain or a dam of the opposite strain. Control litters were left with their own mothers. Offspring were tested for juvenile play at postnatal day 21+/-1, for sociability at 8 weeks of age in an automated three-chambered social approach test, and for self-grooming at 9-11 weeks of age. Results indicate that deficits in play behaviors in juvenile BTBR pups were not rescued by a B6 maternal environment. Similarly, a BTBR maternal environment did not induce play deficits in B6 pups. Cross-fostering had no effect on sociability scores in adults. The high self-grooming in BTBR and low self-grooming in B6 were not affected by maternal environment. These findings favor a genetic interpretation of the unusual social behaviors and self-grooming traits of BTBR, and support the use of the BTBR inbred strain as a mouse model to study genetic mechanism of autism.

Vasoactive intestinal peptide antagonist treatment during mouse embryogenesis impairs social behavior and cognitive function of adult male offspring

Vasoactive intestinal peptide (VIP) is a regulator of rodent embryogenesis during the period of neural tube closure. VIP enhanced growth in whole cultured mouse embryos; treatment with a VIP antagonist during embryogenesis inhibited growth and development. VIP antagonist treatment during embryogenesis also had permanent effects on adult brain chemistry and impaired social recognition behavior in adult male mice. The neurological deficits of autism appear to be initiated during neural tube closure and social behavior deficits are among the key characteristics of this disorder that is more common in males and is frequently accompanied by mental retardation. The current study examined the blockage of VIP during embryogenesis as a model for the behavioral deficits of autism. Treatment of pregnant mice with a VIP antagonist during embryonic days 8 through 10 had no apparent effect on the general health or sensory or motor capabilities of adult offspring. However, male offspring exhibited reduced sociability in the social approach task and deficits in cognitive function, as assessed through cued and contextual fear conditioning. Female offspring did not show these deficiencies. These results suggest that this paradigm has usefulness as a mouse model for aspects of autism as it selectively impairs male offspring who exhibit the reduced social behavior and cognitive dysfunction seen in autism. Furthermore, the study indicates that the foundations of some aspects of social behavior are laid down early in mouse embryogenesis, are regulated in a sex specific manner and that interference with embryonic regulators such as VIP can have permanent effects on adult social behavior.

CD38 regulates oxytocin secretion and complex social behavior

The peptide hormone oxytocin plays a critical role in regulating affiliative behaviors including mating, pair-bond formation, maternal/parenting behavior, social recognition, separation distress and other aspects of attachment. Jin and colleagues recently reported intriguing findings that CD38, a transmembrane receptor with ADP-ribosyl cyclase activity, plays a critical role in maternal nurturing behavior and social recognition by regulating oxytocin secretion. This research may have implications for understanding disorders marked by deficits in social cognition and social functioning, including autism, social anxiety disorder, borderline personality disorder and schizophrenia.