Ifenprodil infusion in agranular insular cortex alters social behavior and vocalizations in rats exposed to moderate levels of ethanol during prenatal development

A population of Insula neurons encodes for social preference only after acute social isolation in mice

The Insula functions as a multisensory relay involved in socio-emotional processing with projections to sensory, cognitive, emotional, and motivational regions. Notably, the interhemispheric projection from the Insula to the contralateral Insula is a robust yet underexplored connection. Using viral-based tracing neuroanatomy, ex vivo and in vivo electrophysiology, in vivo fiber photometry along with targeted circuit manipulation, we elucidated the nature and role of InsulaIns communication in social and anxiety processing in mice. In this study, we 1) characterized the anatomical and molecular profile of the InsulaIns neurons, 2) demonstrated that stimulation of this neuronal subpopulation induces excitation in the Insula interhemispheric circuit, 3) revealed that InsulaIns neurons are essential for social discrimination after 24 h of isolation in male mice. In conclusion, our findings highlight InsulaIns neurons as a distinct class of neurons within the insula and offer new insights into the neuronal mechanisms underlying social behavior.

Sex-specific alterations in cognitive control following moderate prenatal alcohol exposure and transient systemic hypoxia ischemia in the rat

BACKGROUND

Prenatal alcohol exposure (PAE) continues to be a worldwide problem. Affected offspring display impaired neurodevelopment, including difficulties with executive control. Although PAE has also been associated with decreased blood flow to fetuses, the relationship between PAE and altered blood flow is not well understood.

METHODS

We used preclinical models of PAE, transient systemic hypoxia ischemia (TSHI), and PAE + TSHI combined to assess the effects on neurodevelopmental outcomes using translationally relevant touchscreen operant platform testing. Twenty-eight Long-Evans (Blue Spruce, Strain HsdBlu:LE) dams were randomly assigned to one of four experimental groups: Saccharin Control (Sham), 5% Ethanol (PAE), TSHI, or 5% Ethanol and TSHI (PAE + TSHI). Dams consumed either saccharin or 5% ethanol during gestation. TSHI was induced on Embryonic Day 19 (E19) during an open laparotomy where the uterine arteries were transiently occluded for 1 h. Pups were born normally and, after weaning, were separated by sex. A total of 80 offspring, 40 males and 40 females, were tested on the 5-Choice Continuous Performance paradigm (5C-CPT).

RESULTS

Female offspring were significantly impacted by TSHI, but not PAE, with an increase in false alarms and a decrease in hit rates, omissions, accuracy, and correct choice latencies. In contrast, male offspring were mildly affected by PAE, but not TSHI, showing decreases in premature responses and increases in accuracy. No significant interactions between PAE and TSHI were detected on any measure.

CONCLUSION

Transient systemic hypoxia ischemia impaired performance on the 5C-CPT in females, leading to a bias toward stimulus responsivity regardless of stimulus type. In contrast, TSHI did not affect male offspring, and only slight effects of PAE were seen. Together, these data suggest that TSHI in females may cause alterations in cortical structures that override alterations caused by moderate PAE.

Social circuits and their dysfunction in autism spectrum disorder

Social behaviors, how individuals act cooperatively and competitively with conspecifics, are widely seen across species. Rodents display various social behaviors, and many different behavioral paradigms have been used for investigating their neural circuit bases. Social behavior is highly vulnerable to brain network dysfunction caused by neurological and neuropsychiatric conditions such as autism spectrum disorders (ASDs). Studying mouse models of ASD provides a promising avenue toward elucidating mechanisms of abnormal social behavior and potential therapeutic targets for treatment. In this review, we outline recent progress and key findings on neural circuit mechanisms underlying social behavior, with particular emphasis on rodent studies that monitor and manipulate the activity of specific circuits using modern systems neuroscience approaches. Social behavior is mediated by a distributed brain-wide network among major cortical (e.g., medial prefrontal cortex (mPFC), anterior cingulate cortex, and insular cortex (IC)) and subcortical (e.g., nucleus accumbens, basolateral amygdala (BLA), and ventral tegmental area) structures, influenced by multiple neuromodulatory systems (e.g., oxytocin, dopamine, and serotonin). We particularly draw special attention to IC as a unique cortical area that mediates multisensory integration, encoding of ongoing social interaction, social decision-making, emotion, and empathy. Additionally, a synthesis of studies investigating ASD mouse models demonstrates that dysfunctions in mPFC-BLA circuitry and neuromodulation are prominent. Pharmacological rescues by local or systemic (e.g., oral) administration of various drugs have provided valuable clues for developing new therapeutic agents for ASD. Future efforts and technological advances will push forward the next frontiers in this field, such as the elucidation of brain-wide network activity and inter-brain neural dynamics during real and virtual social interactions, and the establishment of circuit-based therapy for disorders affecting social functions.

Stress-altering anterior insular cortex activity affects risk decision-making behavior in mice of different sexes

Stress can affect people's judgment and make them take risky decisions. Abnormal decision-making behavior is a core symptom of psychiatric disorders, such as anxiety, depression, and substance abuse. However, the neuronal mechanisms underlying such impairments are largely unknown. The anterior insular cortex (AIC) is a crucial structure to integrate sensory information with emotional and motivational states. These properties suggest that AIC can influence a subjective prediction in decision-making. In this study, we demonstrated that stressed mice prefer to take more risky choices than control mice using a gambling test. Manipulating the neural activity of AIC or selectively inhibiting the AIC-BLA pathway with chemogenetic intervention resulted in alterations in risk decision-making in mice. Different sexes may have different decision-making strategies in risky situations. Endogenous estrogen levels affect emotional cognition by modulating the stress system function in women. We observed decision-making behavior in mice of different sexes with or without stress experience. The result showed that female mice did not change their choice strategy with increasing risk/reward probability and performed a lower risk preference than male mice after stress. Using the pharmacological method, we bilaterally injected an estrogen receptor (ER) antagonist that resulted in more risky behavior and decreased synaptic plasticity in the AIC of female mice. Our study suggested that the AIC is a crucial region involved in stress-induced alteration of decision-making, and estrogen in the AIC may regulate decision-making behavior by regulating synaptic plasticity.

Moderate prenatal alcohol exposure produces sex-specific social impairments and attenuates prelimbic excitability and amygdala-cortex modulation of adult social behaviour

Lifelong social impairments are common in individuals with prenatal alcohol exposure (PAE), and preclinical studies have identified gestational day (G)12 as a vulnerable timepoint for producing social deficits following binge-level PAE. While moderate (m)PAE also produces social impairments, the long-term neuroadaptations underlying them are poorly understood. Activity of the projection from the basolateral amygdala to the prelimbic cortex (BLA → PL) leads to social avoidance, and the PL is implicated in negative social behaviours, making each of these potential candidates for the neuroadaptations underlying mPAE-induced social impairments. To examine this, we first established that G12 mPAE produced sex-specific social impairments lasting into adulthood in Sprague-Dawley rats. We then chemogenetically inhibited the BLA → PL using clozapine N-oxide (CNO) during adult social testing. This revealed that CNO reduced social investigation in control males but had no effect on mPAE males or females of either exposure, indicating that mPAE attenuated the role of this projection in regulating male social behaviour and highlighting one potential mechanism by which mPAE affects male social behaviour more severely. Using whole-cell electrophysiology, we also examined mPAE-induced changes to PL pyramidal cell physiology and determined that mPAE reduced cell excitability, likely due to increased suppression by inhibitory interneurons. Overall, this work identified two mPAE-induced neuroadaptations that last into adulthood and that may underlie the sex-specific vulnerability to mPAE-induced social impairments. Future research is necessary to expand upon how these circuits modulate both normal and pathological social behaviours and to identify sex-specific mechanisms, leading to differential vulnerability in males and females.

Biological and Acoustic Sex Differences in Rat Ultrasonic Vocalization

The rat model is a useful tool for understanding peripheral and central mechanisms of laryngeal biology. Rats produce ultrasonic vocalizations (USVs) that have communicative intent and are altered by experimental conditions such as social environment, stress, diet, drugs, age, and neurological diseases, validating the rat model's utility for studying communication and related deficits. Sex differences are apparent in both the rat larynx and USV acoustics and are differentially affected by experimental conditions. Therefore, the purpose of this review paper is to highlight the known sex differences in rat USV production, acoustics, and laryngeal biology detailed in the literature across the lifespan.

Encoding of social exploration by neural ensembles in the insular cortex

The insular cortex (IC) participates in diverse complex brain functions, including social function, yet their cellular bases remain to be fully understood. Using microendoscopic calcium imaging of the agranular insular cortex (AI) in mice interacting with freely moving and restrained social targets, we identified 2 subsets of AI neurons—a larger fraction of “Social-ON” cells and a smaller fraction of “Social-OFF” cells—that change their activity in opposite directions during social exploration. Social-ON cells included those that represented social investigation independent of location and consisted of multiple subsets, each of which was preferentially active during exploration under a particular behavioral state or with a particular target of physical contact. These results uncover a previously unknown function of AI neurons that may act to monitor the ongoing status of social exploration while an animal interacts with unfamiliar conspecifics.

The insular cortex participates in diverse complex brain functions, including social function, but their cellular basis remains unclear. This study uses microendoscopic calcium imaging in mice interacting with conspecifics to identify “social cells” in the agranular insular cortex; multiple subsets of neurons encode distinct aspects of ongoing social behavior.

Social and olfactory experiences modify neuronal morphology of orbital frontal cortex

Structural modifications in the dendritic morphology of neurons occur following many forms of experience, including exposure to drugs, complex housing, and training in specific behavioral tasks. The present study examined morphological changes in orbitofrontal (OFC) and medial prefrontal cortex (mPFC) neurons of female rats following experience with a variety of social partners or nonsocial olfactory stimuli. We reasoned that experience with various social partners or olfactory stimuli, and the associated behavioral adaptations, would drive structural modifications in prefrontal cortex neurons engaged by these stimuli. Social experience was manipulated by providing rats with a novel cage-mate or housing the animal with the same cage-mate throughout the study. Similarly, olfactory experience was manipulated by introducing novel, nonsocial odors in the home cage or exposing the animals to the same home-cage odor throughout the study. Both forms of experience resulted in altered dendritic morphology in OFC neurons, whereas morphological changes in mPFC were comparatively small and limited to changes in spine density. These observations indicate that OFC and mPFC neurons respond differently to social and nonsocial olfactory stimulation in adulthood and join the growing body of data illustrating differential effects of experience on structural plasticity in OFC and mPFC. (PsycINFO Database Record (c) 2020 APA, all rights reserved).

Aggressive behavior and brain neuronal activation in sexually naïve male Mongolian gerbils

Aggressive behavior plays an important role in animal's survival and reproductive success. Although there has been growing interests in studying neural mechanisms underlying aggressive behavior using traditional laboratory animal models, little is known about mechanisms controlling naturally occurring aggression in sexually naïve animals. In the present study, we characterized aggressive behavior displayed by sexually naïve male Mongolian gerbils (Meriones unguiculatus) and examined the subsequent neuronal activation in the brain measured by Fos-immunoreactive (Fos-ir) staining. We found that resident males initiated attacks and showed intense levels of aggression (including chase, bite, offensive sideway, lunge and on-top) towards a conspecific male intruder. Furthermore, attacks from the resident males towards the intruder produced a nonrandom distribution of bites, with the most on the rump, flank, back and tail and few on the limbs, ventrum and head. In contrast, control males that were exposed to a woodblock (control for novelty) never attacked the woodblock and showed higher levels of object/environmental investigation. Male gerbils exposed to an intruder had significantly higher levels of Fos-ir density in the medial (MeA) and anterior cortical (ACo) subnuclei of the amygdala, principal nucleus (BSTpr) and interfascicular nucleus (BSTif) of the bed nucleus of the stria terminalis, ventrolateral subdivision of the ventromedial hypothalamus (VMHvl), and paraventricular nucleus of the hypothalamus (PVN), compared to control males. Together, our results indicate that sexually naïve, group housed male gerbils naturally display aggression towards conspecific strangers, and such aggressive behavior is associated with special patterns of neuronal activation in the brain.

An insular view of the social decision-making network

Social animals must detect, evaluate and respond to the emotional states of other individuals in their group. A constellation of gestures, vocalizations, and chemosignals enable animals to convey affect and arousal to others in nuanced, multisensory ways. Observers integrate social information with environmental and internal factors to select behavioral responses to others via a process call social decision-making. The Social Decision Making Network (SDMN) is a system of brain structures and neurochemicals that are conserved across species (mammals, reptiles, amphibians, birds) that are the proximal mediators of most social behaviors. However, how sensory information reaches the SDMN to shape behavioral responses during a social encounter is not well known. Here we review the empirical data that demonstrate the necessity of sensory systems in detecting social stimuli, as well as the anatomical connectivity of sensory systems with each node of the SDMN. We conclude that the insular cortex is positioned to link integrated social sensory cues to this network to produce flexible and appropriate behavioral responses to socioemotional cues.

Long-term Reductions in the Population of GABAergic Interneurons in the Mouse Hippocampus following Developmental Ethanol Exposure

Developmental exposure to ethanol leads to a constellation of cognitive and behavioral abnormalities known as Fetal Alcohol Spectrum Disorders (FASDs). Many cell types throughout the central nervous system are negatively impacted by gestational alcohol exposure, including inhibitory, GABAergic interneurons. Little evidence exists, however, describing the long-term impact of fetal alcohol exposure on survival of interneurons within the hippocampal formation, which is critical for learning and memory processes that are impaired in individuals with FASDs. Mice expressing Venus yellow fluorescent protein in inhibitory interneurons were exposed to vaporized ethanol during the third trimester equivalent of human gestation (postnatal days 2-9), and the long-term effects on interneuron numbers were measured using unbiased stereology at P90. In adulthood, interneuron populations were reduced in every hippocampal region examined. Moreover, we found that a single exposure to ethanol at P7 caused robust activation of apoptotic neurodegeneration of interneurons in the hilus, granule cell layer, CA1 and CA3 regions of the hippocampus. These studies demonstrate that developmental ethanol exposure has a long-term impact on hippocampal interneuron survivability, and may provide a mechanism partially explaining deficits in hippocampal function and hippocampus-dependent behaviors in those afflicted with FASDs.

Calcium chloride mimics the effects of acamprosate on cognitive deficits in chronic alcohol-exposed mice

RATIONALE

Acamprosate (calcium-bis N-acetylhomotaurinate) is the leading medication approved for the maintenance of abstinence, shown to reduce craving and relapse in animal models and human alcoholics. Acamprosate can improve executive functions that are impaired by chronic intermittent ethanol (CIE) exposure. Recent work has suggested that acamprosate's effects on relapse prevention are due to its calcium component, which raises the question whether its pro-cognitive effects are similarly mediated by calcium.

OBJECTIVES

This study examined the effects of acamprosate on alcohol-induced behavioral deficits and compared them with the effects of the sodium salt version of N-acetylhomotaurinate or calcium chloride, respectively.

METHODS

We exposed mice to alcohol via three cycles of CIE and measured changes in alcohol consumption in a limited-access paradigm. We then compared the effects of acamprosate and calcium chloride (applied subchronically for 3 days during withdrawal) in a battery of cognitive tasks that have been shown to be affected by chronic alcohol exposure.

RESULTS

CIE-treated animals showed deficits in attentional set-shifting and deficits in novel object recognition. Alcohol-treated animals showed no impairments in social novelty detection and interaction, or delayed spontaneous alternation. Both acamprosate and calcium chloride ameliorated alcohol-induced cognitive deficits to comparable extents. In contrast, the sodium salt version of N-acetylhomotaurinate did not reverse the cognitive deficits.

CONCLUSIONS

These results add evidence to the notion that acamprosate produces its anti-relapse effects through its calcium moiety. Our results also suggest that improved regulation of drug intake by acamprosate after withdrawal might at least in part be related to improved cognitive function.

Social Order: Using The Sequential Structure of Social Interaction to Discriminate Abnormal Social Behavior in the Rat

Social interactions form the basis of a broad range of functions related to survival and mating. The complexity of social behaviors and the flexibility required for normal social interactions make social behavior particularly susceptible to disruption. The consequences of developmental insults in the social domain and the associated neurobiological factors are commonly studied in rodents. Though methods for investigating social interactions in the laboratory are diverse, animals are typically placed together in an apparatus for a brief period (under 30 min) and allowed to interact freely while behavior is recorded for subsequent analysis. A standard approach to the analysis of social behavior involves quantification of the frequency and duration of individual social behaviors. This approach provides information about the allocation of time to particular behaviors within a session, which is typically sufficient for detection of robust alterations in behavior. Virtually all social species, however, display complex sequences of social behavior that are not captured in the quantification of individual behaviors. Sequences of behavior may provide more sensitive indicators of disruptions in social behavior. Sophisticated analysis systems for quantification of behavior sequences have been available for many years; however, the required training and time to complete these analyses represent significant barriers to high-throughput assessments. We present a simple approach to the quantification of behavioral sequences that requires minimal additional analytical steps after individual behaviors are coded. We implement this approach to identify altered social behavior in rats exposed to alcohol during prenatal development, and show that the frequency of several pairwise sequences of behavior discriminate controls from ethanol-exposed rats when the frequency of individual behaviors involved in those sequences does not. Thus, the approach described here may be useful in detecting subtle deficits in the social domain and identifying neural circuits involved in the organization of social behavior.