Interleukin-1ß-induced inflammation and acetaminophen during infancy: Distinct and interactive effects on social-emotional and repetitive behavior in C57BL/6J mice.

Acetaminophen (APAP) exposure early in life has been associated with increased risk of neurodevelopmental disorders in epidemiological studies. In rodent models, early-life APAP has similarly been shown to produce long-term changes in brain and behavior, including altered activity levels and social behavior. Most rodent studies to date have, nevertheless, attempted to model early-life APAP without considering that most APAP exposure occurs in a context of immune activation and/or fever. To mimic the repeated infections common during infancy, we employed the cytokine interleukin-1ß (IL-1ß) to induce immune activation three times during early postnatal development (i.e., day 5, 8, and 11). On these days, C57BL/6J pups were administered either IL-1ß (0.2 µg/kg) or saline vehicle followed, after 45 min, by either APAP (103.9 mg/kg) or vehicle. Mice were subsequently administered a battery of tests of social-emotional and repetitive behavior. A number of distinct long-term effects of IL-1ß and APAP treatments were found, including sex-specific shifts in repetitive behavior and emotional hyperthermia following early-life IL-1ß and increased social caution in males following early-life APAP. We also observed significant interaction between IL-1ß and APAP: as adults, 'two-hit' IL-1ß + APAP females displayed greater anxiety-related thigmotaxis across a number of tests, including an open field. 'Two hit' males, in turn, showed elevated levels of avoidance of an unfamiliar social partner during a social interaction test. Our results highlight that IL-1ß-induced inflammation and APAP have both distinct effects and significant interactions during early life, with enduring sex-specific effects on phenotypes relevant to neurodevelopmental disorders.

Maternal antibiotics disrupt microbiome, behavior, and temperature regulation in unexposed infant mice.

Maternal antibiotic (ABx) exposure can significantly perturb the transfer of microbiota from mother to offspring, resulting in dysbiosis of potential relevance to neurodevelopmental disorders such as autism spectrum disorder (ASD). Studies in rodent models have found long-term neurobehavioral effects in offspring of ABx-treated dams, but ASD-relevant behavior during the early preweaning period has thus far been neglected. Here, we exposed C57BL/6J mouse dams to ABx (5 mg/ml neomycin, 1.25 µg/ml pimaricin, .075% v/v acetic acid) dissolved in drinking water from gestational day 12 through offspring postnatal day 14. A number of ASD-relevant behaviors were assayed in offspring, including ultrasonic vocalization (USV) production during maternal separation, group huddling in response to cold challenge, and olfactory-guided home orientation. In addition, we obtained measures of thermoregulatory competence in pups during and following behavioral testing. We found a number of behavioral differences in offspring of ABx-treated dams (e.g., modulation of USVs by pup weight, activity while huddling) and provide evidence that some of these behavioral effects can be related to thermoregulatory deficiencies, particularly at younger ages. Our results suggest not only that ABx can disrupt microbiomes, thermoregulation, and behavior, but that metabolic effects may confound the interpretation of behavioral differences observed after early-life ABx exposure.

Elevated ghrelin alters the behavioral effects of perinatal acetaminophen exposure in rats.

A growing body of evidence links prenatal and early postnatal acetaminophen (APAP) exposure to atypical development of brain and behavior. In adult rodents, APAP is known to produce oxidative stress and lower anxiety-related behavior following acute exposure. In models of early-life exposure, APAP has also been shown to alter anxiety-related and other behaviors. Since the neuropeptide ghrelin has been recently shown to reduce oxidative stress markers and act as a neuroprotectant, we hypothesized that exposure to ghrelin prior to exposure to APAP would mitigate the behavioral effects of APAP exposure. On postnatal day 7, pups were administered doses of either APAP (51.97 mg/kg), ghrelin (1 mg/kg/ml), ghrelin + APAP, or vehicle only. As adults, anxiety-related behavior was assessed in the open field and elevated plus maze. Behavior differed based upon treatment condition. In rats unexposed to ghrelin, APAP treatment resulted in increased exploration (i.e., reduced anxiety) in the open field relative to controls. Rats co-administered APAP and ghrelin did not differ from vehicle-only controls. No significant effects of APAP or interactions between APAP and ghrelin exposures were observed in the elevated plus maze. These results are the first to demonstrate that ghrelin can mitigate the effects of perinatal APAP exposure in rats.

Oxytocin and 'social hyperthermia': Interaction with ß3-adrenergic receptor-mediated thermogenesis and significance for the expression of social behavior in male and female mice.

Oxytocin (OT) is a critical regulator of multiple facets of energy homeostasis, including brown adipose tissue (BAT) thermogenesis. Nevertheless, it is unclear what, if any, consequence the thermoregulatory and metabolic effects of OT have for the display of social behavior in adult rodents. Here, we examine the contribution of the OT receptor (OTR) and ß3 adrenergic receptor (ß3AR) to the increase in body temperature that typically accompanies social interaction (i.e., social hyperthermia; SH) and whether SH relates to the expression of social behavior in adult mice. Specifically, we examined how OTR antagonism via peripheral injection of L-368,899 (10 mg/kg) affects the expression of social behavior in C57BL/6J mice, in the presence of active/agonized versus antagonized ß3AR, the receptor known to mediate stress-induced BAT thermogenesis. After drug treatment and a 30 min delay, mice were provided a 10 min social interaction test with an unfamiliar, same-sex conspecific. We hypothesized that OTR and ß3AR/BAT interact to influence behavior during social interaction, with at least some effects of OT on social behavior dependent upon OT's thermal effects via ß3AR/BAT. We found that OTR-mediated temperature elevation is largely responsible for SH during social interaction in mice-albeit not substantially via ß3AR-dependent BAT thermogenesis. Further, our results reveal a complex relationship between OTR, ß3AR, social hyperthermia and the display of specific social behaviors, with SH most closely associated with anxiety and/or vigilance-related behaviors-that is, behaviors that antagonize or interfere with the initiation of close, non-agonistic social behavior.

Hearing Better with the Right Eye? The Lateralization of Multisensory Processing Affects Auditory Learning in Northern Bobwhite Quail (Colinus Virginianus) Chicks.

Precocial avian species exhibit a high degree of lateralization of perceptual and motor abilities, including preferential eye use for tasks such as social recognition and predator detection. Such lateralization has been related, in part, to differential experience prior to hatch. That is, due to spatial and resulting postural constraints late in incubation, one eye and hemisphere-generally the right eye / left hemisphere-receive greater amounts of stimulation than the contralateral eye / hemisphere. This raises the possibility that the left hemisphere may specialize or show relative advantages in integrating information across visual and auditory modalities, given that it typically receives greater amounts of multimodal auditory and visual stimulation prior to hatch. The present study represents an initial investigation of this question in a precocial avian species, the Northern bobwhite quail (Colinus virginianus). Day-old bobwhite chicks received 5 min training sessions in which they vocalized to receive contingent playback of a bobwhite maternal call, presented with or without a light that flashed in synchrony with the notes of the call (i.e., bimodal versus unimodal exposure, respectively). Chicks were trained with or without eye patches that allowed them to experience the visual component of the bimodal stimulus with only the left eye (LE), right eye (RE), or both eyes (i.e., binocular; BIN). Finally, the light was placed in various positions relative to the speakers playing the maternal call across three experiments. 24 hrs later chicks were provided a simultaneous choice test between the familiarized and a novel bobwhite maternal call. Given that the right eye and ear typically face outward and are thus unoccluded by the body during late prenatal development, we hypothesized that RE chicks would show facilitated learning under bimodal conditions compared to all other training conditions. This hypothesis was partially confirmed in Experiment 1, when the light was positioned 40 cm above the source of the maternal call. However, we also observed evidence of suppressed learning in chicks provided BIN exposure to the bimodal audio-visual stimulus that was not present during auditory-only training. Experiments 2 and 3 demonstrated that this was likely related to activation of a left-hemisphere dependent fear response when the left eye was exposed to a visual stimulus that loomed above the auditory stimulus. These results indicate that multisensory processing is lateralized in a precocial bird and that these species may thus provide a unique model for studying experience-dependent plasticity of intersensory perception.

Interleukin-1ß injection causes loss of tail tips in neonatal mice.

Early-life immune challenges and inflammation are risk factors for a range of developmental disorders. During the course of a study examining interactions between the common antipyretic acetaminophen (APAP; paracetamol) and interleukin-1ß (IL-1ß)-induced inflammation in neonatal mice we observed that subcutaneous (s.c.) injection of IL-1ß often leads to significantly shorter, blunt-tipped tails. Three times during early development, on postnatal day 5 (P5), P8, and P11, C57BL/6J pups were given s.c. injection of either .2 µg/kg IL-1ß or 5 cc/kg injection of saline vehicle followed, after a 45 min delay, by a second injection, of either 103.9 mg/kg APAP or saline. IL-1ß was observed to reduce tail length-via a blunting of the tail tip-in treated vs. untreated mice, an effect that was significant as early as P11 and persisted through the end of the study (~P74). Interestingly, IL-1ß-induced tail blunting was significantly lessened by APAP, an interaction that may have occurred as a result of the opposing actions of APAP and IL-1ß on cyclooxygenase-2. Although this specific hypothesis and the mechanisms underlying the effects of IL-1ß on tail length require further study, they add to the literature suggesting that IL-1ß may be a critical mediator of specific adverse effects of early-life inflammation.

Oxytocin and the warm outer glow: Thermoregulatory deficits cause huddling abnormalities in oxytocin-deficient mouse pups.

Oxytocin is a social and reproductive hormone that also plays critical roles in a range of homeostatic processes, including thermoregulation. Here, we examine the role of oxytocin (OT) as a mediator of brown adipose tissue (BAT) thermogenesis, cold-induced huddling, and thermotaxis in eight-day-old (PD8) OT 'knock out' (OTKO) mouse pups. We tested OTKO and wildtype (WT) pups in single- and mixed-genotype groups of six, exposing these to a period of ambient warmth (~35°C) followed by a period of cold (~21.5°C). Whether huddling exclusively with other OTKO or alongside WT pups, OTKO pups showed reduced BAT thermogenesis and were significantly cooler when cold-challenged. Huddles of OTKO pups were also significantly less cohesive than WT huddles during cooling, suggesting that thermoregulatory deficits contribute to contact abnormalities in OTKO pups. To further explore this issue, we examined thermotaxis in individuals and groups of four OTKO or WT pups placed on the cool end of a thermocline and permitted to freely locomote for 2h. When tested individually, male OTKO pups displayed abnormal thermotaxis, taking significantly longer to move up the thermocline and settling upon significantly lower temperatures than WT pups during the 2h test. OTKO mouse pups thus appear to have deficits in both thermogenesis and thermotaxis-the latter deficit being specific to males. Our results add to a growing body of work indicating that OT plays critical roles in thermoregulation and also highlight the entanglement of social and thermoregulatory processes in small mammals such as mice.

ANIMAL COGNITION. Comment on "Number-space mapping in the newborn chick resembles humans' mental number line".

Rugani et al. (Reports, 30 January 2015, p. 534) presented evidence that domestic chicks employ a "mental number line." I argue that the hypothesis testing used to support this claim unjustifiably assumes that domestic chicks are unbiased when choosing between identical stimuli presented to their left and right.

Interoceptive dysfunction: toward an integrated framework for understanding somatic and affective disturbance in depression.

Depression is characterized by disturbed sleep and eating, a variety of other nonspecific somatic symptoms, and significant somatic comorbidities. Why there is such close association between cognitive and somatic dysfunction in depression is nonetheless poorly understood. An explosion of research in the area of interoception-the perception and interpretation of bodily signals-over the last decade nonetheless holds promise for illuminating what have until now been obscure links between the social, cognitive-affective, and somatic features of depression. This article reviews rapidly accumulating evidence that both somatic signaling and interoception are frequently altered in depression. This includes comparative studies showing vagus-mediated effects on depression-like behaviors in rodent models as well as studies in humans indicating both dysfunction in the neural substrates for interoception (e.g., vagus, insula, anterior cingulate cortex) and reduced sensitivity to bodily stimuli in depression. An integrative framework for organizing and interpreting this evidence is put forward which incorporates (a) multiple potential pathways to interoceptive dysfunction; (b) interaction with individual, gender, and cultural differences in interoception; and (c) a developmental psychobiological systems perspective, emphasizing likely differential susceptibility to somatic and interoceptive dysfunction across the lifespan. Combined with current theory and evidence, it is suggested that core symptoms of depression (e.g., anhedonia, social deficits) may be products of disturbed interoceptive-exteroceptive integration. More research is nonetheless needed to fully elucidate the relationship between mind, body, and social context in depression.

Sex differences in thermogenesis structure behavior and contact within huddles of infant mice.

Brown adipose tissue (BAT) is a thermogenic effector abundant in most mammalian infants. For multiparous species such as rats and mice, the interscapular BAT deposit provides both an emergency "thermal blanket" and a target for nestmates seeking warmth, thereby increasing the cohesiveness of huddling groups. Sex differences in BAT regulation and thermogenesis have been documented in a number of species, including mice (Mus musculus)--with females generally exhibiting relative upregulation of BAT. It is nonetheless unknown whether this difference affects the behavioral dynamics occurring within huddles of infant rodents. We investigated sex differences in BAT thermogenesis and its relation to contact while huddling in eight-day-old C57BL/6 mouse pups using infrared thermography, scoring of contact, and causal modeling of the relation between interscapular temperature relative to other pups in the huddle (T IS (rel)) and contacts while huddling. We found that females were warmer than their male siblings during cold challenge, under conditions both in which pups were isolated and in which pups could actively huddle in groups of six (3 male, 3 female). This difference garnered females significantly more contacts from other pups than males during cold-induced huddling. Granger analyses revealed a significant negative feedback relationship between contacts with males and T IS (rel) for females, and positive feedback between contacts with females and T IS (rel) for males, indicating that male pups drained heat from female siblings while huddling. Significant sex assortment nonetheless occurred, such that females made more contacts with other females than expected by chance, apparently outcompeting males for access to each other. These results provide further evidence of enhanced BAT thermogenesis in female mice. Slight differences in BAT can significantly structure the behavioral dynamics occurring in huddles, resulting in differences in the quantity and quality of contacts obtained by the individuals therein, creating sex differences in behavioral interactions beginning in early infancy.

Group and individual regulation of physiology and behavior: a behavioral, thermographic, and acoustic study of mouse development.

The traditional approach to the study of thermoregulation in young animals focuses on the regulatory capacities of individuals, which, for multiparous species, risks ignoring critical aspects of the early developmental niche. Here, we examined the ontogeny of regulatory behavior in C57BL/6 mice, employing simultaneous behavioral, thermographic, and acoustic measures of groups and individual pups. Litters of mice were placed in a chamber on Postnatal Day (PND) 2, 4, or 8, in which the ambient temperature (T(a)) gradually cycled (over 50 min) from warm (36.5°C) to cool (20°C) and back (to 36.5°C). Litters of all three ages displayed "group regulatory behavior," whereby group size varied with changes in T(a). This coupling, moreover, improved with age. Infrared thermography was used to monitor skin temperature of pups' interscapular (T(IS)) and rump (T(rump)) areas, and to estimate brown adipose tissue (BAT) thermogenesis (T(IS)-T(rump)) in PND4 and PND8 individuals and huddles. Huddling was found to significantly reduce heat loss in pups subject to thermal challenge as groups, compared to pups challenged as individuals. Additionally, females were found to display significantly warmer T(IS) and T(rump) values than male huddlemates. Huddling did not have a consistent effect on emissions of ultrasonic vocalizations, which were generally correlated with ambient temperature and BAT activation. Our results indicate that simultaneous measures of behavioral and physiological response to cooling may prove useful for a variety of applications, including the phenotyping of social dysfunction.

Biased embryos: Prenatal experience alters the postnatal malleability of auditory preferences in bobwhite quail.

Many precocial birds show a robust preference for the maternal call of their own species before and after hatching. This differential responsiveness to species-specific auditory stimuli by embryos and neonates has been the subject of study for more than four decades, but much remains unknown about the dynamics of this ability. Gottlieb [Gottlieb [1971]. Development of species identification in birds: An enquiry into the prenatal determinants of perception. Chicago/London: University of Chicago Press.] demonstrated that prenatal exposure to embryonic vocalizations serves to canalize the formation of species-specific preferences in ducklings. Apart from this, little is known about the features of the developmental system that serve to canalize such species-typical preferences, on the one hand, and generate novel behavioral phenotypes, on the other. In the current study, we show that briefly exposing bobwhite quail embryos to a heterospecific Japanese quail (JQ) maternal call significantly enhanced their acquisition of a preference for that call when chicks were provided with subsequent postnatal exposure to the same call. This was true whether postnatal exposure involved playback of the maternal call contingent upon chick contact vocalizations or yoked, non-contingent exposure to the call. Chicks that received both passive prenatal and contingent postnatal exposure to the JQ maternal call redirected their species-typical auditory preference, showing a significant preference for JQ call over the call of their own species. In contrast, chicks receiving only prenatal or only postnatal exposure to the JQ call did not show this redirection of their auditory preference. Our results indicate that prenatal sensory stimulation can significantly bias postnatal responsiveness to social stimuli, thereby altering the course of early learning and memory.

Stimulus contingency and the malleability of species-typical auditory preferences in Northern bobwhite (Colinus virginianus) hatchlings.

Precocial avian hatchlings are typically highly social and show strong species-typical preferences for the maternal calls of their own species. The influence of social contingencies on the acquisition of species-specific preferences has, however, largely been neglected. We found that exposing bobwhite (BW) quail chicks to a Japanese quail (JQ) call contingent on their own vocalizations for 5 min was sufficient to eliminate their species-typical preference for the BW maternal call. Yoked, noncontingent exposure had no such effect. The introduction of variability to the contingency, but not a lengthening of the training session, was found to engender even higher preferences for the JQ call. Chicks provided with contingent exposure to the JQ call on a variable ratio schedule showed a significant preference for the JQ over the BW maternal call, whereas chicks provided with equivalent fixed ratio exposure did not. These results highlight the role that social interaction and contingency can play in the acquisition and maintenance of species-specific auditory preferences in precocial avian species.

Alimentary Epigenetics: A Developmental Psychobiological Systems View of the Perception of Hunger, Thirst and Satiety.

Hunger, thirst and satiety have an enormous influence on cognition, behavior and development, yet we often take for granted that they are simply inborn or innate. Converging data and theory from both comparative and human domains, however, supports the conclusion that the phenomena hunger, thirst and satiety are not innate but rather emerge probabilistically as a function of experience during individual development. The metatheoretical perspective provided by developmental psychobiological systems theory provides a useful framework for organizing and synthesizing findings related to the development of the perception of hunger, thirst and satiety, or alimentary interoception. It is argued that neither developmental psychology nor the psychology of eating and drinking have adequately dealt with the ontogeny of alimentary interoception and that a more serious consideration of the species-typical developmental system of food and fluid intake and the many modifications that have been made therein is likely necessary for a full understanding of both alimentary and emotional development.

Interactive and vicarious acquisition of auditory preferences in Northern bobwhite (Colinus virginianus) chicks.

Studies examining the effects of stimulus contingency on filial imprinting have produced inconsistent findings. In the current study, day-old bobwhite chicks (Colinus virginianus) received individual 5-min sessions in which they were provided contingent, noncontingent, or vicarious exposure to a variant of a bobwhite maternal assembly call. Chicks given contingent exposure to the call showed a significant preference for the familiar call 24 hr following exposure and significantly greater preferences than chicks given noncontingent exposure. Chicks given vicarious exposure to recordings of another chick interacting with the maternal call showed significant deviations from chance responding; however, the direction of chick preference (toward the familiar or unfamiliar) depended on the particular call used. These results indicate that both direct and indirect (vicarious) exposure to stimulus contingency can enhance the acquisition of auditory preferences in precocial avian hatchlings. Precocial avian hatchlings thus likely play a more active role in directing their own perceptual and behavioral development than has typically been thought.