Kumi O. Kuroda

Functional, anatomical, and neurochemical differentiation of medial preoptic area subregions in relation to maternal behavior in the mouse

In rodents, previous findings indicate critical involvement of the medial preoptic area (MPOA) in the neural control of maternal behavior. However, the specification of the particular MPOA subregions involved in maternal behavior and the identification of the neurochemical phenotype(s) of the essential neurons demands additional study. Therefore, we investigated the chemical neuroanatomy of the essential MPOA subregion for maternal behavior in C57BL/6J female mice. Using the oxytocinergic neurons in the dorsal MPOA as a primary regional marker, we first assessed the distribution of c‐Fos‐expressing neurons in the MPOA during maternal behavior using immunohistochemistry. Results showed that non‐oxytocinergic neurons in the dorsal and ventral MPOA prominently expressed c‐Fos during maternal behavior. Then using excitotoxic lesion studies, we determined the specific MPOA area that is necessary for maternal behavior. Bilateral lesions of the central MPOA, where c‐Fos was expressed only moderately, effectively disrupted maternal behavior, although lesions to the dorsal and ventral MPOA regions were ineffective. These centrally lesioned females were highly infanticidal irrespective of their previous maternal experience. Neurochemical investigations showed that more than 75% of the c‐Fos‐expressing neurons in central MPOA were GABAergic. Many of them also expressed galanin, neurotensin, and/or tachykinin2 mRNAs. Finally, the central MPOA was populated by numerous glutamatergic neurons, although only a small percentage of these neurons colocalized with c‐Fos. To conclude, the central MPOA is the indispensable subregion for mouse maternal behavior, and GABAergic and/or peptidergic neurons in this area were transcriptionally activated during maternal behavior. J. Comp. Neurol. 521:1633–1663, 2013.

Behavioral transition from attack to parenting in male mice: a crucial role of the vomeronasal system.

Sexually naive male mice show robust aggressive behavior toward pups. However, the proportion of male mice exhibiting pup-directed aggression declines after cohabitation with a pregnant female for 2 weeks after mating. Subsequently, on becoming fathers, they show parental behavior toward pups, similar to maternal behavior by mothers. To elucidate the neural mechanisms underlying this behavioral transition, we examined brain regions differentially activated in sexually naive males and fathers after exposure to pups, using c-Fos expression as a neuronal activation marker. We found that, after pup exposure, subsets of neurons along the vomeronasal neural pathway—including the vomeronasal sensory neurons, the accessory olfactory bulb, the posterior medial amygdala, the medioposterior division of the bed nucleus of stria terminalis, and the anterior hypothalamic area—were more strongly activated in sexually naive males than in fathers. Notably, c-Fos induction was not observed in the vomeronasal sensory neurons of fathers after pup exposure. Surgical ablation of the vomeronasal organ in sexually naive males resulted in the abrogation of pup-directed aggression and simultaneous induction of parental behavior. These results suggest that chemical cues evoking pup-directed aggression are received by the vomeronasal sensory neurons and activate the vomeronasal neural pathway in sexually naive male mice but not in fathers. Thus, the downregulation of pup pheromone-induced activation of the vomeronasal system might be important for the behavioral transition from attack to parenting in male mice.

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

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

Infant Calming Responses during Maternal Carrying in Humans and Mice

BACKGROUND Mother-infant bonding is the earliest and most critical social relationship of mammalian infants. To promote this bond, infants have innate behaviors to seek maternal proximity and protest upon separation via communication with the mother vocally and through body movement. However, the physiological mechanisms regulating these infant behaviors remain largely undefined. RESULTS Here we show a novel set of infant cooperative responses during maternal carrying. Infants under 6 months of age carried by a walking mother immediately stopped voluntary movement and crying and exhibited a rapid heart rate decrease, compared with holding by a sitting mother. Furthermore, we identified strikingly similar responses in mouse pups as defined by immobility and diminished ultrasonic vocalizations and heart rate. Using pharmacologic and genetic interventions in mouse pups, we identified the upstream and downstream neural systems regulating the calming response. Somatosensory and proprioceptive input signaling are required for induction, and parasympathetic and cerebellar functions mediate cardiac and motor output, respectively. The loss of the calming response hindered maternal rescue of the pups, suggesting a functional significance for the identified calming response. CONCLUSIONS Our study has demonstrated for the first time that the infant calming response to maternal carrying is a coordinated set of central, motor, and cardiac regulations and is a conserved component of mammalian mother-infant interactions. Our findings provide evidence for and have the potential to impact current parenting theory and practice, since unsoothable crying is the major risk factor for child abuse.

Neurobehavioral basis of the impaired nurturing in mice lacking the immediate early gene FosB

The transcription factor FosB is induced in neurons of the medial preoptic area (MPOA) during parenting, through activation of the extracellular signal-regulated kinase (ERK). FosB mutant (-/-) postpartum mice and virgin mice that are exposed to pups show defective nurturing behavior. The FosB (-/-) MPOA fails to fully up-regulate SPRY1 and Rad, the feedback regulators of ERK and calcium signaling, respectively. Here we studied FosB function by examining the gene expression profiles and the behavioral characteristics of FosB (-/-) mice. We found that FosB (-/|-) mice exhibited not only decreased parenting but also decreased infanticide compared with (+/) littermates. We then performed gene expression analysis in the MPOA of FosB (-/-) mice compared with the wild-type littermates. We found up-regulation of glial fibrillary acidic protein (GFAP), C4, and Ela1 mRNA in the MPOA of FosB (-/-) mice; all of these gene products were implicated in general neuropathological conditions. Immunohistochemical analysis showed that up-regulation of GFAP was not restricted to MPOA but extended throughout the forebrain, including the cerebral cortex and striatum. Such pervasive GFAP up-regulation suggested that FosB (-/-) mice might have other behavioral abnormalities than nurturing. Indeed, these mice showed a clear alteration in emotionality, detected by the acoustic startle, elevated plus maze, and passive avoidance tests. These results suggest that FosB (-/-) mice have broader neurobehavioral dysfunctions, with which the nurturing defect might share the common mechanism.

Distinct preoptic-BST nuclei dissociate paternal and infanticidal behavior in mice.

Paternal behavior is not innate but arises through social experience. After mating and becoming fathers, male mice change their behavior toward pups from infanticide to paternal care. However, the precise brain areas and circuit mechanisms connecting these social behaviors are largely unknown. Here we demonstrated that the c‐Fos expression pattern in the four nuclei of the preoptic‐bed nuclei of stria terminalis (BST) region could robustly discriminate five kinds of previous social behavior of male mice (parenting, infanticide, mating, inter‐male aggression, solitary control). Specifically, neuronal activation in the central part of the medial preoptic area (cMPOA) and rhomboid nucleus of the BST (BSTrh) retroactively detected paternal and infanticidal motivation with more than 95% accuracy. Moreover, cMPOA lesions switched behavior in fathers from paternal to infanticidal, while BSTrh lesions inhibited infanticide in virgin males. The projections from cMPOA to BSTrh were largely GABAergic. Optogenetic or pharmacogenetic activation of cMPOA attenuated infanticide in virgin males. Taken together, this study identifies the preoptic‐BST nuclei underlying social motivations in male mice and reveals unexpected complexity in the circuit connecting these nuclei.

FosB Null Mutant Mice Show Enhanced Methamphetamine Neurotoxicity: Potential Involvement of FosB in Intracellular Feedback Signaling and Astroglial Function

Previous studies show that (1) two members of fos family transcription factors, c-Fos and FosB, are induced in frontal brain regions by methamphetamine; (2) null mutation of c-Fos exacerbates methamphetamine-induced neurotoxicity; and (3) null mutation of FosB enhances behavioral responses to cocaine. Here we sought a role of FosB in responses to methamphetamine by studying FosB null mutant (−/−) mice. After a 10 mg/kg methamphetamine injection, FosB(−/−) mice were more prone to self-injury. Concomitantly, the intracellular feedback regulators of Sprouty and Rad-Gem-Kir (RGK) family transcripts had lower expression profiles in the frontoparietal cortex and striatum of the FosB(−/−) mice. Three days after administration of four 10 mg/kg methamphetamine injections, the frontoparietal cortex and striatum of FosB(−/−) mice contained more degenerated neurons as determined by Fluoro-Jade B staining. The abundance of the small neutral amino acids, serine, alanine, and glycine, was lower and/or was poorly induced after methamphetamine administration in the frontoparietal cortex and striatum of FosB(−/−) mice. In addition, methamphetamine-treated FosB(−/−) frontoparietal and piriform cortices showed more extravasation of immunoglobulin, which is indicative of blood–brain barrier dysfunction. Methamphetamine-induced hyperthermia, brain dopamine content, and loss of tyrosine hydroxylase immunoreactivity in the striatum, however, were not different between genotypes. These data indicate that FosB is involved in thermoregulation-independent protective functions against methamphetamine neurotoxicity in postsynaptic neurons. Our findings suggest two possible mechanisms of FosB-mediated neuroprotection: one is induction of negative feedback regulation within postsynaptic neurons through Sprouty and RGK. Another is supporting astroglial function such as maintenance of the blood–brain barrier, and metabolism of serine and glycine, which are important glial modulators of nerve cells.

The medial preoptic area and the regulation of parental behavior

·Research Highlight· The preoptic area (POA) is located in the most anterior part of the hypothalamus and is bordered dorsally by the anterior commissure and anteroventrally by the nucleus of the diagonal band of Broca [1]. Accumulating evidence from developmental neurobiology suggests, however, that the POA may be a separate entity from hypothalamus, and may actually be part of the basal telencephalon [2, 3]. Both the hypothalamus and POA are highly complex and heterogeneous areas, containing multiple nuclei, each of which has specific fundamental functions for survival. Among these, the POA contains nuclei involved in the regulation of blood osmolality and temperature (the median preoptic nucleus), sleep (the ventrolateral preoptic and suprachiasmatic nuclei), ovulation (gonadotropin-releasing hormone neurons scattered mainly in the ventral part of the POA), male sexual behavior (the medial preoptic nucleus), and parental behavior (the central part of the medial POA, cMPOA). Parental behavior in mammals is typically a uniparental maternal care system, while paternal and alloparental behaviors (parental responses toward infants that are not ones biological offspring) are not common. However, paternal and alloparental behaviors do occur in those species where such behaviors have adaptive signifi cance [4, 5]. A critical role of the medial POA (MPOA) in maternal behavior was initially suggested by Fisher [6] , and has been established in a series of studies by Numan [7, 8] in laboratory rats. Then it was confirmed in other rodents, such as hamsters [9] , California mice [10] , and laboratory mice [11] , as well as for paternal and alloparental behaviors [10–13]. The MPOA is also involved in the parental behavior of sheep [14] and presumably most other mammals. Severing the lateral, in particular the dorsolateral, connections of the MPOA disrupts maternal behavior most strongly and specifi cally, compared to cutting the anterior, posterior, or dorsal connections [15, 16]. These findings are consistent with the fact that the major afferent and efferent connections of the rat medial preoptic nucleus, the largest and central nucleus of the MPOA, enter and leave laterally [17]. While postpartum maternal behavior is similar in laboratory rats and mice, alloparental behavior in virgin animals differs quite impressively. Virgin female rats initially avoid, and may even attack, young pups, and they require several days of continuous pup exposure (sensitization) before their behavior switches toward displaying parental responses [18]. Virgin male rats behave similarly [ 18]. In contrast, the majority of virgin female mice …

Assessing Postpartum Maternal Care, Alloparental Behavior, and Infanticide in Mice: With Notes on Chemosensory Influences

Chemosensory signaling influences maternal care and other innate behaviors toward conspecific young animals in rodents. In this chapter, we describe basic protocols for assessment of postpartum maternal behavior and other pup-directed behaviors in laboratory mice. The specific aim of this protocol is to screen out the abnormal phenotypes in parenting of genetic mutant mice under the standard housing condition. The possible underlying mechanisms for a given abnormality in the mother-young interaction are briefly suggested as well.

Transport Response is a filial-specific behavioral response to maternal carrying in C57BL/6 mice

BackgroundA mother carries her young in many altricial mammals, such as cats, lions, rats and mice. During maternal carrying, the transported young assume a compact posture. We have recently shown that, in both humans and mice, the carried infants immediately calmed down and showed reductions in heart rate, distress vocalizations, and voluntary movement. The loss of the calming response in mouse pups hindered maternal retrieval efficacy. These findings suggested that the infant calming response functioned to reduce the maternal burden of carrying and was therefore conserved in a variety of mammalian species. However, it remains unclear how and when each component of this calming response develops and whether it is a filial-specific behavior.ResultsWe dissected various components of the carrying-induced responses in mouse pups, collectively called the “Transport Response” herein. We showed that during the second postnatal week, pups exhibited characteristic compact posture with limb ventroflexion. The body trunk remained paradoxically pliable, suggesting complex neural regulation throughout the body. Pups also showed an increased pain tolerance to a tail pinch during the Transport Response. Analyses of the developmental courses of distinct components of the Transport Response revealed the independent regulation of each component: in the first postnatal week, the cessation of ultrasonic vocalizations was exhibited prominently; in the second postnatal week, immobilization reached its peak; and toward the third postnatal week, the postural component became fully matured. At the end of the third postnatal week, when the pups are able to transport by themselves, the pups no longer exhibited the Transport Response.ConclusionsThis study has revealed the mouse Transport Response as a complex set of behavioral and physiological components, each of which has a specific postnatal time window but is orchestrated in a well-matched manner with the maturation of ambulatory ability in the pups. These findings collectively indicate that the Transport Response is a filial-specific, innate behavioral reaction and is distinct from a simple reflex or defensive freezing response. The Transport Response could be a novel index of primitive filial attachment behaviors, acting to smooth mother-infant interaction.