Preference for cocaine- versus pup-associated cues differentially activates neurons expressing either Fos or cocaine- and amphetamine-regulated transcript in lactating, maternal rodents

Effects of reproductive status on behavioral and neural responses to isolated pup stimuli in female California mice

The transition to motherhood in mammals is marked by changes in females' perception of and responsiveness to sensory stimuli from infants. Our understanding of maternally induced sensory plasticity relies most heavily on studies in uniparental, promiscuous house mice and rats, which may not be representative of rodent species with different life histories. We exposed biparental, monogamous California mouse (Peromyscus californicus) mothers and ovariectomized virgin females to one of four acoustic and olfactory stimulus combinations (Control: clean cotton and white noise; Call: clean cotton and pup vocalizations; Odor: pup-scented cotton and white noise; Call + Odor: pup-scented cotton and pup vocalizations) and quantified females' behavior and Fos expression in select brain regions. Behavior did not differ between mothers and ovariectomized virgins. Among mothers, however, those exposed to the Control condition took the longest to sniff the odor stimulus, and mothers exposed to the Odor condition were quicker to sniff the odor ball compared to those in the Call condition. Behavior did not differ among ovariectomized virgins exposed to the different conditions. Fos expression differed across conditions only in the anterior hypothalamic nucleus (AHN), which responds to aversive stimuli: among mothers, the Control condition elicited the highest AHN Fos and Call + Odor elicited the lowest. Among ovariectomized virgin females, Call elicited the lowest Fos in the AHN. Thus, reproductive status in California mice alters females' behavioral responses to stimuli from pups, especially odors, and results in the inhibition of defense circuitry in response to pup stimuli.

The medial preoptic area and acute cocaine's stimulant effects in rats: Potential influences of estradiol and biological sex

The medial preoptic area (mPOA) in the hypothalamus is an important integrator of neuroendocrine signaling and a key regulator of both natural and drug-induced reward. Although the mPOA modulates sex differences in other behaviors, whether it also modulates sex differences in cocaine response remains unclear. To help us better understand the mPOA's role in sex differences associated with cocaine response, we examined cocaine-induced changes in locomotion and neural activity in the mPOA of male and female rats. In addition, neural activity in the striatum, a brain area known to be involved in cocaine response, was examined for comparison purposes. Fos, the protein product of the immediate early gene c-fos, was used as the marker of neural activity. Locomotion chambers were used to measure behavior, radioimmunoassays and vaginal lavages were used to determine hormonal status, and immunohistochemical assays were used to quantify Fos. To account for the effects of gonadal hormones, rats were left gonadally intact and categorized as either 'low-estradiol' or 'high-estradiol' based on their hormonal status on test day. Results indicate that high-estradiol females experienced greater cocaine-induced mPOA Fos-immunoreactivity (Fos-ir) and displayed greater cocaine-induced locomotion than low estradiol females. Conversely, high-estradiol males experienced less cocaine-induced mPOA Fos-ir and displayed less cocaine-induced locomotion than low-estradiol males. Cocaine-induced Fos-ir in the mPOA also correlated with cocaine-induced Fos-ir in areas of the striatum already associated with cocaine response. These findings further support the mPOA's role in the endocrine-mediated response to cocaine. It also identifies the mPOA as a contributor to sex differences in cocaine response and potential differences in vulnerability to developing cocaine use disorders.

The Protective Effect of Social Reward on Opioid and Psychostimulant Reward and Relapse: Behavior, Pharmacology, and Brain Regions

Until recently, most modern neuroscience research on addiction using animal models did not incorporate manipulations of social factors. Social factors play a critical role in human addiction: social isolation and exclusion can promote drug use and relapse, while social connections and inclusion tend to be protective. Here, we discuss the state of the literature on social factors in animal models of opioid and psychostimulant preference, self-administration, and relapse. We first summarize results from rodent studies on behavioral, pharmacological, and circuit mechanisms of the protective effect of traditional experimenter-controlled social interaction procedures on opioid and psychostimulant conditioned place preference, self-administration, and relapse. Next, we summarize behavioral and brain-mechanism results from studies using newer operant social-interaction procedures that inhibit opioid and psychostimulant self-administration and relapse. We conclude by discussing how the reviewed studies point to future directions for the addiction field and other neuroscience and psychiatric fields, and their implications for mechanistic understanding of addiction and development of new treatments.SIGNIFICANCE STATEMENT In this review, we propose that incorporating social factors into modern neuroscience research on addiction could improve mechanistic accounts of addiction and help close gaps in translating discovery to treatment. We first summarize rodent studies on behavioral, pharmacological, and circuit mechanisms of the protective effect of both traditional experimenter-controlled and newer operant social-interaction procedures. We then discuss potential future directions and clinical implications.

Effects of maternal experience on pup-induced activation of maternal neural circuits in virgin mice

Maternal experience can promote a long-lasting increase in maternal motivation. This maintenance of caregiving behaviors, rather than avoidant or agnostic responses towards young, is advantageous for the survival of subsequent offspring. We have previously reported that maternal motivation is associated with differential immediate early gene expression in central motivation circuits and aversion circuits. Here we ask how these circuits come to differentially respond to infant cues. We used Targeted Recombination in Active Populations (TRAP) to identify cells that respond to pups in maternally hesitant TRAP2;Ai14 virgin female mice. Following an initial 60 min exposure to foster pups, virgin TRAP2;Ai14 mice were injected with 4-hydroxytamoxifen to induce recombination in c-Fos expressing cells and subsequent permanent expression of a red fluorescent reporter. We then examined whether the same cells that encode pup cues are reactivated during maternal memory retrieval two weeks later using c-Fos immunohistochemistry. Whereas initial pup exposure induced c-Fos activation exclusively in the medial preoptic area (MPOA), following repeated experience, c-Fos expression was significantly higher than baseline in multiple regions of maternal and central aversion circuits (e.g., ventral bed nucleus of the stria terminalis, nucleus accumbens, basolateral amygdala, prefrontal cortex, medial amygdala, and ventromedial nucleus of the hypothalamus). Further, cells in many of these sites were significantly reactivated during maternal memory retrieval. These data suggest that cells across both maternal motivation and central aversion circuits are stably responsive to pups and thus may form the cellular representation of maternal memory.

Experience-Regulated Neuronal Signaling in Maternal Behavior

Maternal behavior is shaped and challenged by the changing developmental needs of offspring and a broad range of environmental factors, with evidence indicating that the maternal brain exhibits a high degree of plasticity. This plasticity is displayed within cellular and molecular systems, including both intra- and intercellular signaling processes as well as transcriptional profiles. This experience-associated plasticity may have significant overlap with the mechanisms controlling memory processes, in particular those that are activity-dependent. While a significant body of work has identified various molecules and intracellular processes regulating maternal care, the role of activity- and experience-dependent processes remains unclear. We discuss recent progress in studying activity-dependent changes occurring at the synapse, in the nucleus, and during the transport between these two structures in relation to maternal behavior. Several pre- and postsynaptic molecules as well as transcription factors have been found to be critical in these processes. This role reflects the principal importance of the molecular and cellular mechanisms of memory formation to maternal and other behavioral adaptations.

The impact of social variables in preclinical models of cocaine abuse

At present, there are no US Food and Drug Administration–approved treatments for cocaine use disorders. One consideration for this lack of treatment efficacy stems from the appropriate use of animal models. The premise of this commentary is that social behavior needs to be incorporated in animal models of cocaine use disorder. The goal of this commentary is to describe some of the strengths and limitations of recent preclinical animal models of cocaine abuse which have incorporated social behavior. There are many ways to include social variables into preclinical research, and the study design will depend on the questions asked. Four general types of studies incorporating social factors are described: those involving aggression (that is, maternal neglect and social defeat), modeling, social reward, and social housing, including social isolation. The inclusion of social variables into preclinical research will help identify biobehavioral markers that may lead to an individualized treatment approach that more effectively decreases cocaine use. These studies will aid in the development of novel pharmacotherapies as well as non-pharmacological interventions (for example, punishment, alternative reinforcers, and environmental enrichment) that would be critical for informing policy decisions.

Circuit selectivity in drug versus natural reward seeking behaviors

Substance use disorder (SUD) is characterized, in part by behavior biased toward drug use and away from natural sources of reward (e.g., social interaction, food, sex). The neurobiological underpinnings of SUDs reveal distinct brain regions where neuronal activity is necessary for the manifestation of SUD-characteristic behaviors. Studies that specifically examine how these regions are involved in behaviors motivated by drug versus natural reward allow determinations of which regions are necessary for regulating seeking of both reward types, and appraisals of novel SUD therapies for off-target effects on behaviors motivated by natural reward. Here, we evaluate studies directly comparing regulatory roles for specific brain regions in drug versus natural reward. While it is clear that many regions drive behaviors motivated by all reward types, based on the literature reviewed we propose a set of interconnected regions that become necessary for behaviors motivated by drug, but not natural rewards. The circuitry is selectively necessary for drug seeking includes an Action/Reward subcircuit, comprising nucleus accumbens, ventral pallidum, and ventral tegmental area, a Prefrontal subcircuit comprising prelimbic, infralimbic, and insular cortices, a Stress subcircuit comprising the central nucleus of the amygdala and the bed nucleus of the stria terminalis, and a Diencephalon circuit including lateral hypothalamus. Evidence was mixed for nucleus accumbens shell, insular cortex, and ventral pallidum. Studies for all other brain nuclei reviewed supported a necessary role in regulating both drug and natural reward seeking. Finally, we discuss emerging strategies to further disambiguate the necessity of brain regions in drug- versus natural reward-associated behaviors.

Altered responsiveness to pups in virgin female mice of the BTBR strain: Insights from pattern of c-Fos expression in brain regions involved in maternal behavior

BTBR is an inbred mouse strain that displays several behavioral alterations resembling the core symptoms of Autism Spectrum Disorder, including deficit in sociability. In the present study, we investigated whether the pup-induced maternal behavior in virgin female mice, a naturally rewarding behavior, is impaired in this strain similarly to social interaction with adult conspecifics. We firstly assessed the maternal responsiveness towards newly born pups expressed by either virgin female mice of the BTBR strain or of the normo-social B6 strain. Next, we examined in both strains the expression of c-Fos as a marker of neuronal activity in selected brain areas involved in the regulation of maternal behavior in rodents including the olfactory bulb, the medial preoptic area and the paraventricular nucleus (PVN). We also examined the effects of pup presentation on oxytocinergic neurons of the PVN, the major brain site of synthesis of oxytocin, which has a pivotal role in facilitation of maternal response and social responsiveness in general. As a final step, we assessed the c-Fos expression pattern comparing the effect of exposure to pups with that induced by exposure to another social stimulus, focusing on other areas implicated in maternal responsiveness as well as in the affective component of social behavior such as pyriform cortex and central and basolateral amygdala. Our data showed that BTBR virgin females are less responsive to presentation of pups in comparison to B6, in parallel with lower activation of brain areas implicated in the maternal and social responsiveness.

A Scientometric Approach to Review the Role of the Medial Preoptic Area (MPOA) in Parental Behavior

Research investigating the neural substrates underpinning parental behaviour has recently gained momentum. Particularly, the hypothalamic medial preoptic area (MPOA) has been identified as a crucial region for parenting. The current study conducted a scientometric analysis of publications from 1 January 1972 to 19 January 2021 using CiteSpace software to determine trends in the scientific literature exploring the relationship between MPOA and parental behaviour. In total, 677 scientific papers were analysed, producing a network of 1509 nodes and 5498 links. Four major clusters were identified: “C-Fos Expression”, “Lactating Rat”, “Medial Preoptic Area Interaction” and “Parental Behavior”. Their content suggests an initial trend in which the properties of the MPOA in response to parental behavior were studied, followed by a growing attention towards the presence of a brain network, including the reward circuits, regulating such behavior. Furthermore, while attention was initially directed uniquely to maternal behavior, it has recently been extended to the understanding of paternal behaviors as well. Finally, although the majority of the studies were conducted on rodents, recent publications broaden the implications of previous documents to human parental behavior, giving insight into the mechanisms underlying postpartum depression. Potential directions in future works were also discussed.

Identifying signaling genes in spatial single-cell expression data

MOTIVATION

Recent technological advances enable the profiling of spatial single-cell expression data. Such data present a unique opportunity to study cell-cell interactions and the signaling genes that mediate them. However, most current methods for the analysis of these data focus on unsupervised descriptive modeling, making it hard to identify key signaling genes and quantitatively assess their impact.

RESULTS

We developed a Mixture of Experts for Spatial Signaling genes Identification (MESSI) method to identify active signaling genes within and between cells. The mixture of experts strategy enables MESSI to subdivide cells into subtypes. MESSI relies on multi-task learning using information from neighboring cells to improve the prediction of response genes within a cell. Applying the methods to three spatial single-cell expression datasets, we show that MESSI accurately predicts the levels of response genes, improving upon prior methods and provides useful biological insights about key signaling genes and subtypes of excitatory neuron cells.

AVAILABILITY AND IMPLEMENTATION

MESSI is available at: https://github.com/doraadong/MESSI.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

The dynamic regulation of appetitive behavior through lateral hypothalamic orexin and melanin concentrating hormone expressing cells

The lateral hypothalamic area (LHA) is a heterogeneous brain structure extensively studied for its potent role in regulating energy balance. The anatomical and molecular diversity of the LHA permits the orchestration of responses to energy sensing cues from the brain and periphery. Two of the primary cell populations within the LHA associated with integration of this information are Orexin (ORX) and Melanin Concentrating Hormone (MCH). While both of these non-overlapping populations exhibit orexigenic properties, the activities of these two systems support feeding behavior through contrasting mechanisms. We describe the anatomical and functional properties as well as interaction with other neuropeptides and brain reward and hedonic systems. Specific outputs relating to arousal, food seeking, feeding, and metabolism are coordinated through these mechanisms. We then discuss how both the ORX and MCH systems harmonize in a divergent yet overall cooperative manner to orchestrate feeding behavior through transitions between various appetitive states, and thus offer novel insights into LHA allostatic control of appetite.

Neural Circuit Mechanisms That Underlie Parental Care

In mammals, parental care is essential for the survival of the young; therefore, it is vitally important to the propagation of the species. These behaviors, differing between the two sexes, are innate, stereotyped, and are also modified by an individual's reproductive experience. These characteristics suggest that neural mechanisms underlying parental behaviors are genetically hardwired, evolutionarily conserved as well as sexually differentiated and malleable to experiential changes. Classical lesion studies on neural control of parental behaviors, mostly done in rats, date back to the 1950s. Recent developments of new methods and tools in neuroscience, which allow precise targeting and activation/inhibition of specific populations of neurons and their projections to different brain structures, have afforded fresh opportunities to dissect and delineate the detailed neural circuit mechanisms that govern distinct components of parental behaviors in the genetically tractably organism, the laboratory mouse (Mus musculus). In this review, we summarize recent discoveries using modern neurobiological tools within the context of traditional lesion studies. In addition, we discuss interesting cross talk between neural circuits that govern parent care with those that regulate other innate behaviors such as feeding and mating.

Adaptations in reward-related behaviors and mesolimbic dopamine function during motherhood and the postpartum period

Initiation and maintenance of maternal behavior is driven by a complex interaction between the physiology of parturition and offspring stimulation, causing functional changes in maternal brain and behavior. Maternal behaviors are among the most robust and rewarding motivated behaviors. Mesolimbic dopamine (DA) system alterations during pregnancy and the postpartum enable enhanced reward-related responses to offspring stimuli. Here, we review behavioral evidence demonstrating postpartum rodents exhibit a bias towards pups and pup-related stimuli in reward-related tasks. Next, we provide an overview of normative adaptations in the mesolimbic DA system induced by parturition and the postpartum, which likely mediate shifts in offspring valence. We also discuss a causal link between dopaminergic dysfunction and disrupted maternal behaviors, which are recapitulated in postpartum depression (PPD) and relevant rodent models. In sum, mesolimbic DA system activation drives infant-seeking behavior and strengthens the mother-infant bond, potentially representing a therapeutic target for reward-related deficits in PPD.

Neurophysiological and cognitive changes in pregnancy

The hormonal fluctuations in pregnancy drive a wide range of adaptive changes in the maternal brain. These range from specific neurophysiological changes in the patterns of activity of individual neuronal populations, through to complete modification of circuit characteristics leading to fundamental changes in behavior. From a neurologic perspective, the key hormone changes are those of the sex steroids, estradiol and progesterone, secreted first from the ovary and then from the placenta, the adrenal glucocorticoid cortisol, as well as the anterior pituitary peptide hormone prolactin and its pregnancy-specific homolog placental lactogen. All of these hormones are markedly elevated during pregnancy and cross the blood-brain barrier to exert actions on neuronal populations through receptors expressed in specific regions. Many of the hormone-induced changes are in autonomic or homeostatic systems. For example, patterns of oxytocin and prolactin secretion are dramatically altered to support novel physiological functions. Appetite is increased and feedback responses to metabolic hormones such as leptin and insulin are suppressed to promote a positive energy balance. Fundamental physiological systems such as glucose homeostasis and thermoregulation are modified to optimize conditions for fetal development. In addition to these largely autonomic changes, there are also changes in mood, behavior, and higher processes such as cognition. This chapter summarizes the hormonal changes associated with pregnancy and reviews how these changes impact on brain function, drawing on examples from animal research, as well as available information about human pregnancy.

Raising overlapping litters: Differential activation of rat maternal neural circuitry after interacting with newborn or juvenile pups

The maternal behaviour of a rat dynamically changes during the postpartum period, adjusting to the characteristics and physiological needs of the pups. This adaptation has been attributed to functional modifications in the maternal circuitry. Maternal behaviour can also flexibly adapt according to different litter compositions. Thus, mothers with two overlapping litters can concurrently take care of neonate and juvenile pups, mostly directing their attention to the newborns. We hypothesised that the maternal circuitry of these mothers would show a differential activation pattern after interacting with pups depending on the developmental stage of their offspring. Thus, we evaluated the activation of several areas of the maternal circuitry in mothers of overlapping litters, using c-Fos immunoreactivity as a marker of neuronal activation, after interacting with newborns or juveniles. The results showed that mothers with overlapping litters display different behavioural responses towards their newborn and their juvenile pups. Interestingly, these behavioural displays co-occurred with specific patterns of activation of the maternal neural circuitry. Thus, a similar expression of c-Fos was observed in some key brain areas of mothers that interacted with newborns or juveniles, such as the medial preoptic area and the nucleus accumbens, whereas a differential activation was quantified in the ventral region of the bed nucleus of the stria terminalis, the infralimbic and prelimbic subregions of the medial prefrontal cortex and the basolateral and medial nuclei of the amygdala. We posit that the specific profile of activation of the neural circuitry controlling maternal behaviour in mothers with overlapping litters enables dams to respond adequately to the newborn and the juvenile pups.

Challenges to the parental brain: Neuroethological and translational considerations

Extending from research documenting adaptive parental responses in nonthreatening contexts, the influences of various neuroethological and physiological challenges on effective parenting responses are considered in the current review. In natural habitats, rodent family units are exposed to predators, compromised resources, and other environmental stressors that disrupt HPA axis functions. With the additional physiological demands associated with caring for offspring, alterations in stress-related neuroendocrine responsiveness contribute to adaptive responses in many challenging contexts. Some environmental contexts, however, such as restricted nesting resources, result in disrupted maternal responses that have a negative impact on offspring wellbeing. Additionally, parental dysregulation associated with exposure to environmental chemicals or pharmacological substances, also compromise maternal responses with effects that often extend to future generations. Continued preclinical and clinical research elucidating parental responses to various stressors and physiological disruptors is necessary to provide valuable translational information identifying threats to effective parenting outcomes.

Neuroendocrinology and Adaptive Physiology of Maternal Care

Parental care is critical for offspring survival in many species. In mammals, parental care is primarily provided through maternal care, due to obligate pregnancy and lactation constraints, although some species also show paternal and alloparental care. These behaviors are driven by specialized neural circuits that receive sensory, cortical, and hormonal input to generate a coordinated and timely change in behavior, and sustain that behavior through activation of reward pathways. Importantly, the hormonal changes associated with pregnancy and lactation also act to coordinate a broad range of physiological changes to support the mother and enable her to adapt to the demands of these states. This chapter will review the neural pathways that regulate maternal behavior, the hormonal changes that occur during pregnancy and lactation, and how these two facets merge together to promote both young-directed maternal responses (including nursing and grooming) and young-related responses (including maternal aggression and other physiological adaptions to support the development of and caring for young). We conclude by examining how experimental animal work has translated into knowledge of human parenting, particularly in regards to maternal mental health issues.

The circadian gene Nr1d1 in the mouse nucleus accumbens modulates sociability and anxiety-related behaviour

Nuclear receptor subfamily 1, group D, member 1 (Nr1d1) (also known as Rev-erb alpha) has been linked to circadian rhythm regulation, mood-related behaviour and disorders associated with social deficits. Recent work from our laboratory found striking decreases in Nr1d1 in the nucleus accumbens (NAc) in the maternal condition and indirect evidence that Nr1d1 was interacting with numerous addiction and reward-related genes to modulate social reward. In this study, we applied our insights from the maternal state to nonparental adult mice to determine whether decreases in Nr1d1 expression in the NAc via adeno-associated viral (AAV) vectors and short hairpin RNA (shRNA)-mediated gene knockdown were sufficient to modulate social behaviours and mood-related behaviours. Knockdown of Nr1d1 in the NAc enhanced sociability and reduced anxiety, but did not affect depressive-like traits in female mice. In male mice, Nr1d1 knockdown had no significant behavioural effects. Microarray analysis of Nr1d1 knockdown in females identified changes in circadian rhythm and histone deacetylase genes and suggested possible drugs, including histone deacetylase inhibitors, that could mimic actions of Nr1d1 knockdown. Quantitative real-time PCR (qPCR) analysis confirmed expression upregulation of gene period circadian clock 1 (Per1) and period circadian clock 2 (Per2) with Nr1d1 knockdown. The evidence for roles for opioid-related genes opioid receptor, delta 1 (Oprd1) and preproenkephalin (Penk) was also found. Together, these results suggest that Nr1d1 in the NAc modulates sociability and anxiety-related behaviour in a sex-specific manner, and circadian, histone deacetylase and opioid-related genes may be involved in the expression of these behavioural phenotypes.

Sex differences in motivated behaviors in animal models

Sex differences exist in the motivation for sexual behavior, food, parental care and motivation to take drugs. There are also sex differences in the likelihood of exhibiting motivational disorders such as anhedonia, depression, addictive behavior, and eating disorders. This brief review summaries recent studies on sex differences in all motivated behaviors in social and non-social contexts, focusing on animal models. We also discuss the roles of gonadal hormones and the nonapeptides (nine amino acid peptides) in modulating sex differences in motivation. We propose that sex differences in the neural mechanisms mediating endogenous motivation for food, sex, partners and care of offspring underlie sex differences in all motivated behaviors.

Mothers with substance addictions show reduced reward responses when viewing their own infant's face

Maternal addiction constitutes a major public health problem affecting children, with high rates of abuse, neglect, and foster care placement. However, little is known about the ways in which substance addiction alters brain function related to maternal behavior. Prior studies have shown that infant face cues activate similar dopamine-associated brain reward regions to substances of abuse. Here, we report on a functional MRI study documenting that mothers with addictions demonstrate reduced activation of reward regions when shown reward-related cues of their own infants. Thirty-six mothers receiving inpatient treatment for substance addiction were scanned at 6 months postpartum, while viewing happy and sad face images of their own infant compared to those of a matched unknown infant. When viewing happy face images of their own infant, mothers with addictions showed a striking pattern of decreased activation in dopamine- and oxytocin-innervated brain regions, including the hypothalamus, ventral striatum, and ventromedial prefrontal cortex-regions in which increased activation has previously been observed in mothers without addictions. Our results are the first to demonstrate that mothers with addictions show reduced activation in key reward regions of the brain in response to their own infant's face cues. Hum Brain Mapp 38:5421-5439, 2017. © 2017 Wiley Periodicals, Inc.

Place preferences associated with pups or cocaine change the expression of D2R, V1aR and OTR in the NAcc and MeA and the levels of plasma AVP, OT, T and E2 in mandarin vole fathers

Drug abuse often has negative impacts on parenting behavior. The dopamine (DA), arginine vasopressin (AVP) and oxytocin (OT) systems are involved in paternal behavior and drug-induced behaviors. Mandarin voles (Microtus mandarinus) are socially monogamous rodents with high levels of paternal behavior. The aims of this study were to examine the protein expression levels of the DA 2-type receptor (D2R), AVP receptor 1A(V1aR) and OT receptor (OTR) in the nucleus accumbens (NAcc) and medial amygdala (MeA) as well as the plasma hormone responses after mandarin vole fathers were conditioned with their pups or cocaine. Our experimental models are based on the conditioned place preference (CPP) paradigm. We observed CPP in response to either pup- or cocaine-associated cues in the mandarin vole fathers. Fathers that were conditioned to either pups or cocaine had a lower expression of D2R and V1aR in the NAcc than did controls. Fathers that were conditioned to pups had higher levels of OTR expression in the MeA and higher plasma levels of AVP, OT, estradiol (E2), and lower plasma levels of testosterone (T) than did controls. Fathers that were conditioned to cocaine exhibited lower levels of plasma AVP and T. These results indicate that the reward effects of pup and cocaine are both mediated by D2R, V1aR and OTR in the NAcc and MeA and that there are subtle differences between the pup and cocaine reward mechanisms that are associated with altered plasma AVP, OT, T and E2.

Pup exposure facilitates retrieving behavior via the oxytocin neural system in female mice

Parental behavior in mammals is innate, but it is also facilitated by social experience, specifically social interactions between the parent and infant. Social interactions with infants also induce the alloparental behavior of virgin animals. Oxytocin (OT) plays an important role in mediating alloparental behavior. Although parental behavior is modulated by the medial preoptic area (MPOA) and adjacent regions, it is unclear how OT acts in these regions as a control mechanism of alloparental behavior promoted by adult-pup interaction. The aim of this study was to investigate the role of OT for facilitating effects of adult-pup interactions on alloparental behavior via neural activity of preoptic area (POA), including MPOA and adjacent area. For this purpose, we conducted behavioral tests and examined the neural activity of the OT system in POA. Virgin female mice that were repeatedly exposed to pups showed shorter retrieving latencies and higher number of c-Fos expressing neurons in POA, particular in lateral preoptic area (LPO) compared to control animals that were exposed to pups only one time. In addition, repeated pup exposure increased the proportion of OT neurons and OTR neurons expressing c-Fos in POA. The concentration of OT also significantly increased in the POA. Finally, infusion of an OT antagonist into the POA area blocked the facilitating effects of repeated pup exposure on retrieving behavior. These results demonstrated that the facilitating effects of repeated pup exposure on alloparental behavior occurred via an organizational role of the OT system.

Activation of oxytocin receptors, but not arginine-vasopressin V1a receptors, in the ventral tegmental area of male Syrian hamsters is essential for the reward-like properties of social interactions

Social reward plays a fundamental role in shaping human and animal behavior. The rewarding nature of many forms of social behavior including sexual behavior, parental behavior, and social play has been revealed using well-established procedures such as the conditioned place preference test. Many motivated social behaviors are regulated by the nonapeptides oxytocin (OT) and arginine vasopressin (AVP) through their actions in multiple brain structures. Interestingly, there are few data on whether OT or AVP might contribute to the rewarding properties of social interaction by their actions within brain structures that play a key role in reward mechanisms such as the ventral tegmental area (VTA). The goal of the present study was to investigate the role of OT and AVP in the VTA in regulating the reward-like properties of social interactions. Social interactions between two male hamsters reduced a spontaneous place avoidance in hamsters injected with saline control. Interestingly, however, OT and AVP injected into the VTA induced a significant two-fold reduction in place avoidance for the social interaction chamber when compared to control injections of vehicle. Finally, because OT and AVP can act on each other's receptors to influence social behavior, we also injected highly selective OTR and V1aR agonists and antagonists to determine whether OT or AVP V1a receptors were responsible for mediating the effects of these neuropeptides on social reward. Our results not only demonstrated that OT and AVP activate OTRs and not V1aRs to mediate social reward, they also demonstrated that the activation of OT receptors in the VTA is essential for the expression of the rewarding properties of social interactions.

Genetic and neuroendocrine regulation of the postpartum brain

Changes in expression of hundreds of genes occur during the production and function of the maternal brain that support a wide range of processes. In this review, we synthesize findings from four microarray studies of different maternal brain regions and identify a core group of 700 maternal genes that show significant expression changes across multiple regions. With those maternal genes, we provide new insights into reward-related pathways (maternal bonding), postpartum depression, social behaviors, mental health disorders, and nervous system plasticity/developmental events. We also integrate the new genes into well-studied maternal signaling pathways, including those for prolactin, oxytocin/vasopressin, endogenous opioids, and steroid receptors (estradiol, progesterone, cortisol). A newer transcriptional regulation model for the maternal brain is provided that incorporates recent work on maternal microRNAs. We also compare the top 700 genes with other maternal gene expression studies. Together, we highlight new genes and new directions for studies on the postpartum brain.

Neural mechanisms of mother-infant bonding and pair bonding: Similarities, differences, and broader implications

This article is part of a Special Issue "Parental Care". Mother-infant bonding is a characteristic of virtually all mammals. The maternal neural system may have provided the scaffold upon which other types of social bonds in mammals have been built. For example, most mammals exhibit a polygamous mating system, but monogamy and pair bonding between mating partners occur in ~5% of mammalian species. In mammals, it is plausible that the neural mechanisms that promote mother-infant bonding have been modified by natural selection to establish the capacity to develop a selective bond with a mate during the evolution of monogamous mating strategies. Here we compare the details of the neural mechanisms that promote mother-infant bonding in rats and other mammals with those that underpin pair bond formation in the monogamous prairie vole. Although details remain to be resolved, remarkable similarities and a few differences between the mechanisms underlying these two types of bond formation are revealed. For example, amygdala and nucleus accumbens-ventral pallidum (NA-VP) circuits are involved in both types of bond formation, and dopamine and oxytocin actions within NA appear to promote the synaptic plasticity that allows either infant or mating partner stimuli to persistently activate NA-VP attraction circuits, leading to an enduring social attraction and bonding. Further, although the medial preoptic area is essential for maternal behavior, its role in pair bonding remains to be determined. Our review concludes by examining the broader implications of this comparative analysis, and evidence is provided that the maternal care system may have also provided the basic neural foundation for other types of strong social relationships, beyond pair bonding, in mammals, including humans.

Brain Reward Pathway Dysfunction in Maternal Depression and Addiction: A Present and Future Transgenerational Risk

Two research areas that could benefit from a greater focus on the role of the reward pathway are maternal depression and maternal addiction. Both depression and addiction in mothers are mediated by deficiencies in the reward pathway and represent substantial risks to the health of offspring and future generations. This targeted review discusses maternal reward deficits in depressed and addicted mothers, neural, genetic, and epigenetic mechanisms, and the transgenerational transmission of these deficits from mother to offspring. Postpartum depression and drug use disorders may entail alterations in the reward pathway, particularly in striatal and prefrontal areas, which may affect maternal attachment to offspring and heighten the risk of transgenerational effects on the oxytocin and dopamine systems. Alterations may involve neural circuitry changes, genetic factors that impact monoaminergic neurotransmission, as well as growth factors such as BDNF and stress-associated signaling in the brain. Improved maternal reward-based preventative measures and treatments may be specifically effective for mothers and their offspring suffering from depression and/or addiction.

Common and divergent psychobiological mechanisms underlying maternal behaviors in non-human and human mammals

Maternal interactions with young occupy most of the reproductive period for female mammals and are absolutely essential for offspring survival and development. The hormonal, sensory, reward-related, emotional, cognitive and neurobiological regulators of maternal caregiving behaviors have been well studied in numerous subprimate mammalian species, and some of the importance of this body of work is thought to be its relevance for understanding similar controls in humans. We here review many of the important biopsychological influences on maternal behaviors in the two best studied non-human animals, laboratory rats and sheep, and directly examine how the conceptual framework established by some of the major discoveries in these animal "models" do or do not hold for our understanding of human mothering. We also explore some of the limits for extrapolating from non-human animals to humans. We conclude that there are many similarities between non-human and human mothers in the biological and psychological factors influencing their early maternal behavior and that many of the differences are due to species-characteristic features related to the role of hormones, the relative importance of each sensory system, flexibility in what behaviors are exhibited, the presence or absence of language, and the complexity of cortical function influencing caregiving behaviors.

Addiction and reward-related genes show altered expression in the postpartum nucleus accumbens

Motherhood involves a switch in natural rewards, whereby offspring become highly rewarding. Nucleus accumbens (NAC) is a key CNS region for natural rewards and addictions, but to date no study has evaluated on a large scale the events in NAC that underlie the maternal change in natural rewards. In this study we utilized microarray and bioinformatics approaches to evaluate postpartum NAC gene expression changes in mice. Modular Single-set Enrichment Test (MSET) indicated that postpartum (relative to virgin) NAC gene expression profile was significantly enriched for genes related to addiction and reward in five of five independently curated databases (e.g., Malacards, Phenopedia). Over 100 addiction/reward related genes were identified and these included: Per1, Per2, Arc, Homer2, Creb1, Grm3, Fosb, Gabrb3, Adra2a, Ntrk2, Cry1, Penk, Cartpt, Adcy1, Npy1r, Htr1a, Drd1a, Gria1, and Pdyn. ToppCluster analysis found maternal NAC expression profile to be significantly enriched for genes related to the drug action of nicotine, ketamine, and dronabinol. Pathway analysis indicated postpartum NAC as enriched for RNA processing, CNS development/differentiation, and transcriptional regulation. Weighted Gene Coexpression Network Analysis (WGCNA) identified possible networks for transcription factors, including Nr1d1, Per2, Fosb, Egr1, and Nr4a1. The postpartum state involves increased risk for mental health disorders and MSET analysis indicated postpartum NAC to be enriched for genes related to depression, bipolar disorder (BPD), and schizophrenia. Mental health related genes included: Fabp7, Grm3, Penk, and Nr1d1. We confirmed via quantitative PCR Nr1d1, Per2, Grm3, Penk, Drd1a, and Pdyn. This study indicates for the first time that postpartum NAC involves large scale gene expression alterations linked to addiction and reward. Because the postpartum state also involves decreased response to drugs, the findings could provide insights into how to mitigate addictions.

Using animal models to study post-partum psychiatric disorders

The post-partum period represents a time during which all maternal organisms undergo substantial plasticity in a wide variety of systems in order to ensure the well-being of the offspring. Although this time is generally associated with increased calmness and decreased stress responses, for a substantial subset of mothers, this period represents a time of particular risk for the onset of psychiatric disorders. Thus, post-partum anxiety, depression and, to a lesser extent, psychosis may develop, and not only affect the well-being of the mother but also place at risk the long-term health of the infant. Although the risk factors for these disorders, as well as normal peripartum-associated adaptations, are well known, the underlying aetiology of post-partum psychiatric disorders remains poorly understood. However, there have been a number of attempts to model these disorders in basic research, which aim to reveal their underlying mechanisms. In the following review, we first discuss known peripartum adaptations and then describe post-partum mood and anxiety disorders, including their risk factors, prevalence and symptoms. Thereafter, we discuss the animal models that have been designed in order to study them and what they have revealed about their aetiology to date. Overall, these studies show that it is feasible to study such complex disorders in animal models, but that more needs to be done in order to increase our knowledge of these severe and debilitating mood and anxiety disorders.

CART in the brain of vertebrates: circuits, functions and evolution

Cocaine- and amphetamine-regulated transcript peptide (CART) with its wide distribution in the brain of mammals has been the focus of considerable research in recent years. Last two decades have witnessed a steady rise in the information on the genes that encode this neuropeptide and regulation of its transcription and translation. CART is highly enriched in the hypothalamic nuclei and its relevance to energy homeostasis and neuroendocrine control has been understood in great details. However, the occurrence of this peptide in a range of diverse circuitries for sensory, motor, vegetative, limbic and higher cortical areas has been confounding. Evidence that CART peptide may have role in addiction, pain, reward, learning and memory, cognition, sleep, reproduction and development, modulation of behavior and regulation of autonomic nervous system are accumulating, but an integration has been missing. A steady stream of papers has been pointing at the therapeutic potentials of CART. The current review is an attempt at piecing together the fragments of available information, and seeks meaning out of the CART elements in their anatomical niche. We try to put together the CART containing neuronal circuitries that have been conclusively demonstrated as well as those which have been proposed, but need confirmation. With a view to finding out the evolutionary antecedents, we visit the CART systems in sub-mammalian vertebrates and seek the answer why the system is shaped the way it is. We enquire into the conservation of the CART system and appreciate its functional diversity across the phyla.

Cocaine-associated odor cue re-exposure increases blood oxygenation level dependent signal in memory and reward regions of the maternal rat brain

BACKGROUND

Cue triggered relapse during the postpartum period can negatively impact maternal care. Given the high reward value of pups in maternal rats, we designed an fMRI experiment to test whether offspring presence reduces the neural response to a cocaine associated olfactory cue.

METHODS

Cocaine conditioned place preference was carried out before pregnancy in the presence of two distinct odors that were paired with cocaine or saline (+Cue and -Cue). The BOLD response to +Cue and -Cue was measured in dams on postpartum days 2-4. Odor cues were delivered to dams in the absence and then the presence of pups.

RESULTS

Our data indicate that several limbic and cognitive regions of the maternal rat brain show a greater BOLD signal response to a +Cue versus -Cue. These include dorsal striatum, prelimbic cortex, parietal cortex, habenula, bed nucleus of stria terminalis, lateral septum and the mediodorsal and the anterior thalamic nucleus. Of the aforementioned brain regions, only the parietal cortex of cocaine treated dams showed a significant modulatory effect of pup presence. In this area of the cortex, cocaine exposed maternal rats showed a greater BOLD activation in response to the +Cue in the presence than in the absence of pups.

CONCLUSIONS

Specific regions of the cocaine exposed maternal rat brain are strongly reactive to drug associated cues. The regions implicated in cue reactivity have been previously reported in clinical imaging work, and previous work supports their role in various motivational and cognitive functions.

New theoretical and experimental approaches on maternal motivation in mammals

Maternal behavior is expressed in different modalities, physiological conditions, and contexts. It is the result of a highly motivated brain, that allows the female to flexibily adapt her caring activities to different situations and social demands. To understand how mothers coordinate maternal and other motivated behaviors we discuss the limitations of current theoretical approaches to study maternal motivation (e.g. distinction between appetitive and consummatory behaviors), and propose a different approach (i.e. motorically active vs. passive motivations) and a distinction between maternal motivated state and maternal motivated behaviors. We review the evidence supporting dopamine mediation of maternal motivation and describe how different phases of the dopaminergic response - basal, tonic, and phasic release in the nucleus accumbens - relate to increased salience, invigorating behavior, and behavioral switching. The existing and new experimental paradigms to investigate maternal motivation, and its coexpression and coordination with other social or non-social motivations are also analyzed. An example of how specificity of motivational systems (e.g. maternal and sexual behavior at postpartum estrus) could be processed at the neural level is also provided. This revision offers new theoretical and experimental approaches to address the fundamental question of how mothers flexibly adapt and coordinate the different components of maternal behavior with other motivated behaviors, also critical for the survival of the species.

Effects of cocaine on maternal behavior and neurochemistry

Drug addiction is a chronic relapsing disorder that involves drug seeking and abuse despite the negative social and health consequences. While the potential effects of cocaine on child development have been extensively studied over the last 30 years, few researchers have focused on the effects of cocaine on maternal behavior, which includes offspring care and maternal aggression towards an unfamiliar individual. In humans, maternal cocaine use can lead to child neglect, abuse, and disrupt the mother-child bond. While it has been argued the developmental effects of maternal cocaine use on children were initially overstated, it is clear that disruptions of typical maternal behavior (i.e. postpartum depression, anxiety disorders) are detrimental to the physical and emotional health of offspring. Cocaine use in mothers is commonly associated with psychological disorders, including depression and anxiety, and it is postulated that many of the negative effects of maternal cocaine use on offspring are mediated through changes in maternal behavior. This review will summarize research on cocaine and maternal behavior in animal and human studies, discuss potential mechanisms, and suggest therapeutic strategies for treating cocaine-affected maternal behavior which may improve the physical and behavioral health of both mother and child. The primary objective is to stimulate future communication, cooperation, and collaboration between researchers who use animals and humans to study cocaine and maternal behavior.

Many mouths to feed: the control of food intake during lactation

Providing nutrients to their developing young is perhaps the most energetically demanding task facing female mammals. In this paper we focus primarily on studies carried out in rats to describe the changes in the maternal brain that enable the dam to meet the energetic demands of her offspring. In rats, providing milk for their litter is associated with a dramatic increase in caloric intake, a reduction in energy expenditure and changes in the pattern of energy utilization as well as storage. These behavioral and physiological adaptations result, in part, from alterations in the central pathways controlling energy balance. Differences in circulating levels of metabolic hormones such as leptin, ghrelin and insulin as well as in responsiveness to these signals between lactating and nonlactating animals, contribute to the modifications in energy balance pathways seen postpartum. Suckling stimulation from the pups both directly, and through the hormonal state that it induces in the mother, plays a key role in facilitating these adaptations.

Reinforcing properties of pups versus cocaine for fathers and associated central expression of Fos and tyrosine hydroxylase in mandarin voles (Microtus mandarinus)

The reciprocal interaction of pups and cocaine on reward effects in rodent mothers is known. However,it remains unclear whether such effects are apparent in father-offspring bonding. The mandarin vole (Microtus mandarinus) is a monogamous rodent with a high level of paternal care. We investigated the reinforcing properties of pups on vole fathers using a conditioned place preference paradigm across the postpartum period and looked for interactions and differences between the reinforcing effects of pups and cocaine. We also measured neuronal Fos and tyrosine hydroxylase (TH) expression underlying the preferences of fathers for pups or cocaine. Our data showed that fathers developed strong preferences for pups at various times (postnatal day 5–9, 13–17 and 19–23) without cocaine conditioning. Fathers showed a reduced preference for pups following simultaneous conditioning with cocaine. Although they preferred cocaine over postnatal day (PND) 5–9 pups, this preference was not detected for PND 13–17 pups. Fathers preferring cocaine exhibited an increase in Fos-immunoreactive neurons in the accumbens,medial nucleus of the amygdala, cingulate cortex, medial preoptic area and ventral tegmental area and had more TH-IR neurons in the ventral tegmental area compared to fathers preferring PND 5–9 pups. These results showed that similar to cocaine, mandarin vole pups elicit significant reward value to their fathers, but that paternal motivation is impaired by cocaine. A preference for cocaine over pups arose from the release of more dopamine and activation of a greater number of neurons within specific reward-associated neuronal subsets.

Firing patterns of maternal rat prelimbic neurons during spontaneous contact with pups

Extracellular single unit activity was recorded from medial prefrontal cortex (mPFC) of postpartum dams over the course of 3 days while they engaged in spontaneous pup-directed behaviors and non-specific exploratory behavior. Out of 109 units identified over the course of the experiment, 15 units were observed to be pup-responsive and 15 increased their discharge rates non-specifically while not attending to pups. An association between neuronal activity and typical maternal behaviors (e.g., retrieval, pup-grooming, nursing) was not observed. Instead, brief bouts of snout contact with pups were accompanied by phasic increases and decreases in spike rates. The observed pup contact responsive cells might play a role in processing of sensory feedback from pups or the transmission of modulatory output to other subcortical maternal brain areas.

Prefrontal cell firing in male rats during approach towards sexually receptive female: interactions with cocaine

The medial prefrontal cortex (mPFC) plays a role in anticipation of rewards and goal orientation, properties that are influenced by cocaine administration. Single-unit firing was measured in the mPFC of seven male rats during the expression of approach responses toward a sexually receptive female. Nose-poking in male rats was used as a measure of approach behavior during the following periods: a baseline, first exposure to a female, a second baseline 2 h later and a second exposure to female 10 min after cocaine (15 mg kg⁻¹ i.p.). Two types of excitatory responses were identified. First, a subset of cells (23%) showed increased firing activity during nose-poke behavior upon presentation of the female, but not before. Another subset of cells (12%) showed increased firing in the presence of the female only after cocaine was administered. The present results provide preliminary evidence for neurons in the mPFC that are involved in sexually motivated approach behavior and that are modulated by cocaine.

Functional mapping of the neural circuitry of rat maternal motivation: effects of site-specific transient neural inactivation

The present review focuses on recent studies from our laboratory examining the neural circuitry subserving rat maternal motivation across postpartum. We employed a site-specific neural inactivation method by infusion of bupivacaine to map the maternal motivation circuitry using two complementary behavioural approaches: unconditioned maternal responsiveness and choice of pup- over cocaine-conditioned incentives in a concurrent pup/cocaine choice conditioned place preference task. Our findings revealed that, during the early postpartum period, distinct brain structures, including the medial preoptic area, ventral tegmental area and medial prefrontal cortex infralimbic and anterior cingulate subregions, contribute a pup-specific bias to the motivational circuitry. As the postpartum period progresses and the pups grow older, it is further revealed that maternal responsiveness becomes progressively less dependent on the medial preoptic area and medial prefrontal cortex infralimbic activity, and more distributed in the maternal circuitry, such that additional network components, including the medial prefrontal cortex prelimbic subregion, are recruited with maternal experience, and contribute to the expression of late postpartum maternal behaviour. Collectively, our findings provide strong evidence that the remarkable ability of postpartum females to successfully care for their developing infants is subserved by a distributed neural network that carries out efficient and dynamic processing of complex, constantly changing incoming environmental and pup-related stimuli, ultimately allowing the progression of appropriate expression and waning of maternal responsiveness across the postpartum period.

The autism diagnosis in translation: shared affect in children and mouse models of ASD

In the absence of molecular biomarkers that can be used to diagnose ASD, current diagnostic tools depend upon clinical assessments of behavior. Research efforts with human subjects have successfully utilized standardized diagnostic instruments, which include clinician interviews with parents and direct observation of the children themselves [Risi et al., 2006]. However, because clinical instruments are semi-structured and rely heavily on dynamic social processes and clinical skill, scores from these measures do not necessarily lend themselves directly to experimental investigations into the causes of ASD. Studies of the neurobiology of autism require experimental animal models. Mice are particularly useful for elucidating genetic and toxicological contributions to impairments in social function [Halladay et al., 2009]. Behavioral tests have been developed that are relevant to autism [Crawley, 2004, 2007], including measures of repetitive behaviors [Lewis, Tanimura, Lee, & Bodfish, 2007; Moy et al., 2008], social behavior [Brodkin, 2007; Lijam et al., 1997; Moretti, Bouwknecht, Teague, Paylor, & Zoghbi, 2005], and vocal communication [D'Amato et al., 2005; Panksepp et al., 2007; Scattoni et al., 2008]. Advances also include development of high-throughput measures of mouse sociability that can be used to reliably compare inbred mouse strains [Moy et al., 2008; Nadler et al., 2004], as well as measures of social reward [Panksepp & Lahvis, 2007] and empathy [Chen, Panksepp, & Lahvis, 2009; Langford et al., 2006]. With continued generation of mouse gene-targeted mice that are directly relevant to genetic linkages in ASD, there remains an urgent need to utilize a full suite of mouse behavioral tests that allows for a comprehensive assessment of the spectrum of social difficulties relevant to ASD. Using impairments in shared affect as an example, this paper explores potential avenues for collaboration between clinical and basic scientists, within an amply considered translational framework.

Disruption of maternal parenting circuitry by addictive process: rewiring of reward and stress systems

Addiction represents a complex interaction between the reward and stress neural circuits, with increasing drug use reflecting a shift from positive reinforcement to negative reinforcement mechanisms in sustaining drug dependence. Preclinical studies have indicated the involvement of regions within the extended amygdala as subserving this transition, especially under stressful conditions. In the addictive situation, the reward system serves to maintain habitual behaviors that are associated with the relief of negative affect, at the cost of attenuating the salience of other rewards. Therefore, addiction reflects the dysregulation between core reward systems, including the prefrontal cortex (PFC), ventral tegmental area (VTA), and nucleus accumbens (NAc), as well as the hypothalamic-pituitary-adrenal axis and extended amygdala of the stress system. Here, we consider the consequences of changes in neural function during or following addiction on parenting, an inherently rewarding process that may be disrupted by addiction. Specifically, we outline the preclinical and human studies that support the dysregulation of reward and stress systems by addiction and the contribution of these systems to parenting. Increasing evidence suggests an important role for the hypothalamus, PFC, VTA, and NAc in parenting, with these same regions being those dysregulated in addiction. Moreover, in addicted adults, we propose that parenting cues trigger stress reactivity rather than reward salience, and this may heighten negative affect states, eliciting both addictive behaviors and the potential for child neglect and abuse.

Neuromolecular basis of parental behavior in laboratory mice and rats: with special emphasis on technical issues of using mouse genetics

To support the well-being of the parent-infant relationship, the neuromolecular mechanisms of parental behaviors should be clarified. From neuroanatomical analyses in laboratory rats, the medial preoptic area (MPOA) has been shown to be of critical importance in parental retrieving behavior. More recently, various gene-targeted mouse strains have been found to be defective in different aspects of parental behaviors, contributing to the identification of molecules and signaling pathways required for the behavior. Therefore, the neuromolecular basis of "mother love" is now a fully approachable research field in modern molecular neuroscience. In this review, we will provide a summary of the required brain areas and gene for parental behavior in laboratory mice (Mus musculus) and rats (Rattus norvegicus). Basic protocols and technical considerations on studying the mechanism of parental behavior using genetically-engineered mouse strains will also be presented.

Communication impairments in mice lacking Shank1: reduced levels of ultrasonic vocalizations and scent marking behavior

Autism is a neurodevelopmental disorder with a strong genetic component. Core symptoms are abnormal reciprocal social interactions, qualitative impairments in communication, and repetitive and stereotyped patterns of behavior with restricted interests. Candidate genes for autism include the SHANK gene family, as mutations in SHANK2 and SHANK3 have been detected in several autistic individuals. SHANK genes code for a family of scaffolding proteins located in the postsynaptic density of excitatory synapses. To test the hypothesis that a mutation in SHANK1 contributes to the symptoms of autism, we evaluated Shank1(-/-) null mutant mice for behavioral phenotypes with relevance to autism, focusing on social communication. Ultrasonic vocalizations and the deposition of scent marks appear to be two major modes of mouse communication. Our findings revealed evidence for low levels of ultrasonic vocalizations and scent marks in Shank1(-/-) mice as compared to wildtype Shank1(+/+) littermate controls. Shank1(-/-) pups emitted fewer vocalizations than Shank1(+/+) pups when isolated from mother and littermates. In adulthood, genotype affected scent marking behavior in the presence of female urinary pheromones. Adult Shank1(-/-) males deposited fewer scent marks in proximity to female urine than Shank1(+/+) males. Call emission in response to female urinary pheromones also differed between genotypes. Shank1(+/+) mice changed their calling pattern dependent on previous female interactions, while Shank1(-/-) mice were unaffected, indicating a failure of Shank1(-/-) males to learn from a social experience. The reduced levels of ultrasonic vocalizations and scent marking behavior in Shank1(-/-) mice are consistent with a phenotype relevant to social communication deficits in autism.

Annual Research Review: All mothers are not created equal: neural and psychobiological perspectives on mothering and the importance of individual differences

Quality of mothering relies on the integrity of multiple physiological and behavioral systems and on two maternal factors, one proximal and one distal, that have a great impact on how a mother mothers: postpartum depression and early experiences. To mother appropriately requires the action of systems that regulate sensation, perception, affect, reward, executive function, motor output and learning. When a mother is at risk to engage in less than optimal mothering, such as when she is depressed or has experienced adversity in childhood, the function of many or all of maternal and related systems may be affected. In this paper, we will review what is currently known about the biological basis of mothering, with attention to literature on hormones but with a particular focus on recent advances in the fields of functional neuroimaging. Instead of discussing strictly 'maternal' brain imaging studies, we instead use a systems approach to survey important findings relevant to brain systems integral to and/or strongly related to the mothering experience: (a) social behavior; (b) reward and affect; (c) executive function; and (d) maternal behavior. We find that there are many commonalities in terms of the brain regions identified across these systems and, as we would expect, all are sensitive to the influence of, or function differently in the context of, depression and adverse early experience. It is likely that the similarity and cross-talk between maternal, affect and stress systems, observed behaviorally, hormonally and in the context of brain function, allows for mood disturbance and early adverse experiences to have a significant impact on the quality of mothering and the motivation to mother.