Basolateral amygdala and stress-induced hyperexcitability affect motivated behaviors and addiction

Glutamatergic CYLD deletion leads to aberrant excitatory activity in the basolateral amygdala: association with enhanced cued fear expression

JOURNAL/nrgr/04.03/01300535-202511000-00029/figure1/v/2024-12-20T164640Z/r/image-tiff Neuronal activity, synaptic transmission, and molecular changes in the basolateral amygdala play critical roles in fear memory. Cylindromatosis (CYLD) is a deubiquitinase that negatively regulates the nuclear factor kappa-B pathway. CYLD is well studied in non-neuronal cells, yet under-investigated in the brain, where it is highly expressed. Emerging studies have shown involvement of CYLD in the remodeling of glutamatergic synapses, neuroinflammation, fear memory, and anxiety- and autism-like behaviors. However, the precise role of CYLD in glutamatergic neurons is largely unknown. Here, we first proposed involvement of CYLD in cued fear expression. We next constructed transgenic model mice with specific deletion of Cyld from glutamatergic neurons. Our results show that glutamatergic CYLD deficiency exaggerated the expression of cued fear in only male mice. Further, loss of CYLD in glutamatergic neurons resulted in enhanced neuronal activation, impaired excitatory synaptic transmission, and altered levels of glutamate receptors accompanied by over-activation of microglia in the basolateral amygdala of male mice. Altogether, our study suggests a critical role of glutamatergic CYLD in maintaining normal neuronal, synaptic, and microglial activation. This may contribute, at least in part, to cued fear expression.

Adiponectin receptor 1-mediated basolateral amygdala-prelimbic cortex circuit regulates methamphetamine-associated memory

The association between drug-induced rewards and environmental cues represents a promising strategy to address addiction. However, the neural networks and molecular mechanisms orchestrating methamphetamine (MA)-associated memories remain incompletely characterized. In this study, we demonstrated that AdipoRon (AR), a specific adiponectin receptor (AdipoR) agonist, inhibits the formation of MA-induced conditioned place preference (CPP) in MA-conditioned mice, accompanied by suppression of basolateral amygdala (BLA) CaMKIIα neuron activity. Furthermore, we identified an association between the excitatory circuit from the BLA to the prelimbic cortex (PrL) and the integration of MA-induced rewards with environmental cues. We also determined that the phosphorylated AMPK (p-AMPK)/Cav1.3 signaling pathway mediates the modulatory effects of AdipoR1 in PrL-projecting BLA CaMKIIα neurons on the formation of MA reward memories, a process influenced by physical exercise. These findings highlight the critical function of AdipoR1 in the BLACaMKIIα→PrLCaMKIIα circuit in regulating MA-related memory formation, suggesting a potential target for managing MA use disorders.

Sex-specific fear acquisition following early life stress is linked to amygdala and hippocampal purine and glutamate metabolism

Early life stress (ELS) can negatively impact health, increasing the risk of stress-related disorders, such as post-traumatic stress disorder (PTSD). Importantly, PTSD disproportionately affects women, emphasizing the critical need to explore how sex differences influence the genetic and metabolic neurobiological pathways underlying trauma-related behaviors. This study uses the limited bedding and nesting (LBN) paradigm to model ELS and investigate its sex-specific effects on fear memory formation. Employing innovative unsupervised behavioral classification, the current study reveals distinct behavioral patterns associated with fear acquisition and retrieval in male and female mice following ELS. Females exposed to LBN display heightened active fear responses, contrasting with males. Furthermore, the study examined the crucial link between behavioral regulation and cellular metabolism in key brain regions involved in fear and stress processing. Sex-specific and stress-dependent alterations were observed in purine, pyrimidine, and glutamate metabolism within the basolateral amygdala, the dorsal hippocampus, and the ventral hippocampus. These findings provide crucial insights into the complex interplay between metabolic pathways, the neurobiological underpinnings of fear memory, and stress responses. Importantly, they emphasize the significance of considering sex-specific metabolic alterations when investigating stress-related disorders, opening potential avenues for the development of targeted interventions.

The regulative role and mechanism of BNST in anxiety disorder

Anxiety disorders, common yet impactful emotional disturbances, significantly affect physical and mental health globally. Many neuron circuits are associated with anxiety regulation like septo-hippocampal loop, amygdala(AMYG), bed nucleus of the stria terminalis (BNST), ventral hippocampus (vHPC), and brain regions like medial prefrontal cortex (mPFC). However, the concrete mechanism of anxiety disorder in BNST is relatively unknown. Recent research showed BNST plays a critical role in modulating anxiety owing to its anatomical location and special circuit characteristics, which are considered to be a hub in the limbic system regulating anxiety. BNST consists with multiple subregions, which can project separately into different brain regions and exert projecting independently to various brain regions with distinct regulatory effects. Moreover, multiple signal pathways in BNST are reported to play significant roles in regulating anxiety and stress behavior. This review briefly describes anxiety disorders and subdivisions and functions of BNST, focusing on the main neural circuits that serve as fundamental pathways in both the genesis and potential treatment of anxiety disorders and the molecular mechanism of BNST on anxiety. The complexity of structures and mechanisms has facilitated the development of imaging techniques. Innovative multimodal imaging techniques, such as functional magnetic resonance imaging (fMRI) and positron emission tomography (PET), have non-invasively illuminated BNST activities and their functional connections with other brain areas. These methodologies provide a deeper understanding of how BNST responds to anxiety-inducing stimuli, offering invaluable insights into its complex role in anxiety regulation. The continued exploration of BNST in anxiety research promises not only to elucidate fundamental neurobiological mechanisms but also to foster advancements in clinical treatments for anxiety disorders.

The impact of limited sucrose intake on perineuronal nets of parvalbumin interneurons in the basolateral amygdala: A potential role in stress resilience

Natural rewards like regular sucrose consumption can buffer physiological and behavioral stress responses, likely mediated, at least in part, by increased plasticity in parvalbumin-positive (PV+) interneurons in the basolateral amygdala (BLA). As PV+ interneuron plasticity is tightly regulated by specialized extracellular matrix structures called perineuronal nets (PNNs), this study investigated the impact of regular sucrose consumption vs. repetitive stress on the PNNs that surround PV+ interneurons in the BLA, as well as the number of glutamatergic (vGLUT1) and GABAergic (vGAT) appositions that PV+ cells receive. Male rats were given an established limited sucrose intake (LSI) feeding paradigm (vs. water-fed controls) and were co-exposed to a brief restraint stress (vs. no stress controls), daily for 14 days. Sucrose consumption increased the proportion of PV+ cells that were surrounded by PNNs, independent of stress exposure. PV+ cells with PNNs had more vGLUT1-positive and fewer vGAT-positive appositions compared to those lacking PNNs. Additionally, sucrose consumption increased the ratio of excitatory/inhibitory appositions onto PV+ cells, suggesting the possibility of elevated PV+ interneuron tone, leading to greater inhibition of the BLA's stress-excitatory output. These findings indicate that sucrose consumption influences PNN formation and structural plasticity on PV+ interneurons in the BLA, which has implications for understanding the neurological mechanisms underlying stress resilience by natural rewards.

The administration of a phentolamine infusion into the basolateral amygdala enhances long-term memory and diminishes anxiety-like behavior in stressed rats

The basolateral amygdala (BLA) contains adrenergic receptors, which are known to be involved in stress, anxiety, and memory. The objective of this study was to explore whether inhibition of α-adrenergic receptors (by phentolamine, an α-adrenergic receptor antagonist) in the BLA can reduce foot-shock stress-induced anxiety-like behavior, memory deficits, and long-term potentiation (LTP) deficits within the CA1 region of the rat hippocampus. Forty male Wistar rats were assigned to the intact, control, stress (Str), Phent (phentolamine), and Phent + Str groups. Animals were subjected to six shocks on 4 consecutive days, and phentolamine was injected into BLA 20 min before the animals were placed in the foot-shock stress apparatus. Results from the elevated plus maze test (EPM) revealed a reduction in anxiety-like behaviors (by an increased number of entries into the open arm, percentage of time spent in the open arm, and rearing and freezing) among stressed animals upon receiving injections of phentolamine into the BLA. The open-field test results (increased rearing, grooming, and freezing behaviors) were consistent with the EPM test results. Phentolamine infusion into the BLA enhanced spatial memory, reducing errors in finding the target hole and decreasing latency time in the Barnes maze test for stress and nonstress conditions. Injecting phentolamine into the BLA on both sides effectively prevented LTP impairment in hippocampal CA1 neurons after being subjected to foot-shock stress. It has been suggested that phentolamine in the BLA can effectively improve anxiety-like behaviors and memory deficits induced by foot-shock stress.

Oral fentanyl consumption and withdrawal impairs fear extinction learning and enhances basolateral amygdala principal neuron excitatory-inhibitory balance in male and female mice

The number of opioid overdose deaths has increased over the past several years, mainly driven by an increase in the availability of highly potent synthetic opioids, like fentanyl, in the un-regulated drug supply. Over the last few years, changes in the drug supply, and in particular the availability of counterfeit pills containing fentanyl, have made oral use of opioids a more common route of administration. Here, we used a drinking in the dark (DiD) paradigm to model oral fentanyl self-administration using increasing fentanyl concentrations in male and female mice over 5 weeks. Fentanyl consumption peaked in both female and male mice at the 30 μg/mL dose, with female mice consuming significantly more fentanyl than male mice. Mice consumed sufficient fentanyl such that withdrawal was precipitated with naloxone, with males having increased withdrawal symptoms as compared to females, despite lower pharmacological exposure. We also performed behavioral assays to measure avoidance behavior and reward-seeking during fentanyl abstinence. Female mice displayed reduced avoidance behaviors in the open field assay, whereas male mice showed increased avoidance in the light/dark box assay. Female mice also exhibited increased reward-seeking in the sucrose preference test. Fentanyl-consuming mice of both sexes showed impaired cued fear extinction learning following fear conditioning and increased excitatory synaptic drive and increased excitability of BLA principal neurons. Our experiments demonstrate that long-term oral fentanyl consumption results in wide-ranging physiological and behavioral disruptions. This model could be useful to further study fentanyl withdrawal syndrome and behaviors and neuroplasticity associated with protracted fentanyl withdrawal.

The therapeutic potential of low-intensity focused ultrasound for treating substance use disorder

Substance use disorder (SUD) is a persistent public health issue that necessitates the exploration of novel therapeutic interventions. Low-intensity focused ultrasound (LIFU) is a promising modality for precise and invasive modulation of brain activity, capable of redefining the landscape of SUD treatment. The review overviews effective LIFU neuromodulatory parameters and molecular mechanisms, focusing on the modulation of reward pathways in key brain regions in animal and human models. Integration of LIFU with established therapeutics holds promise for augmenting treatment outcomes in SUD. The current research examines LIFU's efficacy in reducing cravings and withdrawal symptoms. LIFU shows promise for reducing cravings, modulating reward circuitry, and addressing interoceptive dysregulation and emotional distress. Selecting optimal parameters, encompassing frequency, burst patterns, and intensity, is pivotal for balancing therapeutic efficacy and safety. However, inconsistencies in empirical findings warrant further research on optimal treatment parameters, physiological action mechanisms, and long-term effects. Collaborative interdisciplinary investigations are imperative to fully realize LIFU's potential in revolutionizing SUD treatment paradigms and enhancing patient outcomes.

Neuroprotective actions of norepinephrine in neurological diseases

Precise control of norepinephrine (NE) levels and NE-receptor interaction is crucial for proper function of the brain. Much evidence for this view comes from experimental studies that indicate an important role for NE in the pathophysiology and treatment of various conditions, including cognitive dysfunction, Alzheimer's disease, Parkinson's disease, multiple sclerosis, and sleep disorders. NE provides neuroprotection against several types of insults in multiple ways. It abrogates oxidative stress, attenuates neuroinflammatory responses in neurons and glial cells, reduces neuronal and glial cell activity, promotes autophagy, and ameliorates apoptotic responses to a variety of insults. It is beneficial for the treatment of neurodegenerative diseases because it improves the generation of neurotrophic factors, promotes neuronal survival, and plays an important role in the regulation of adult neurogenesis. This review aims to present the evidence supporting a principal role for NE in neuroprotection, and molecular mechanisms of neuroprotection.

Alterations in GABAA receptor-mediated inhibition triggered by status epilepticus and their role in epileptogenesis and increased anxiety

The triggers of status epilepticus (SE) in non-epileptic patients can vary widely, from idiopathic causes to exposure to chemoconvulsants. Regardless of its etiology, prolonged SE can cause significant brain damage, commonly resulting in the development of epilepsy, which is often accompanied by increased anxiety. GABAA receptor (GABAAR)-mediated inhibition has a central role among the mechanisms underlying brain damage and the ensuing epilepsy and anxiety. During SE, calcium influx primarily via ionotropic glutamate receptors activates signaling cascades which trigger a rapid internalization of synaptic GABAARs; this weakens inhibition, exacerbating seizures and excitotoxicity. GABAergic interneurons are more susceptible to excitotoxic death than principal neurons. During the latent period of epileptogenesis, the aberrant reorganization in synaptic interactions that follow interneuronal loss in injured brain regions, leads to the formation of hyperexcitable, seizurogenic neuronal circuits, along with disturbances in brain oscillatory rhythms. Reduction in the spontaneous, rhythmic "bursts" of IPSCs in basolateral amygdala neurons is likely to play a central role in anxiogenesis. Protecting interneurons during SE is key to preventing both epilepsy and anxiety. Antiglutamatergic treatments, including antagonism of calcium-permeable AMPA receptors, can be expected to control seizures and reduce excitotoxicity not only by directly suppressing hyperexcitation, but also by counteracting the internalization of synaptic GABAARs. Benzodiazepines, as delayed treatment of SE, have low efficacy due to the reduction and dispersion of their targets (the synaptic GABAARs), but also because themselves contribute to further reduction of available GABAARs at the synapse; furthermore, benzodiazepines may be completely ineffective in the immature brain.

A dual-pathway architecture enables chronic stress to disrupt agency and promote habit formation

Chronic stress can change how we learn and, thus, how we make decisions. Here we investigated the neuronal circuit mechanisms that enable this. Using a multifaceted systems neuroscience approach in male and female mice, we reveal a dual pathway, amygdala-striatal neuronal circuit architecture by which a recent history of chronic stress disrupts the action-outcome learning underlying adaptive agency and promotes the formation of inflexible habits. We found that the basolateral amygdala projection to the dorsomedial striatum is activated by rewarding events to support the action-outcome learning needed for flexible, goal-directed decision making. Chronic stress attenuates this to disrupt action-outcome learning and, therefore, agency. Conversely, the central amygdala projection to the dorsomedial striatum mediates habit formation. Following stress this pathway is progressively recruited to learning to promote the premature formation of inflexible habits. Thus, stress exerts opposing effects on two amygdala-striatal pathways to disrupt agency and promote habit. These data provide neuronal circuit insights into how chronic stress shapes learning and decision making, and help understand how stress can lead to the disrupted decision making and pathological habits that characterize substance use disorders and mental health conditions.

Subregion-specific transcriptomic profiling of rat brain reveals sex-distinct gene expression impacted by adolescent stress

Stress during adolescence clearly impacts brain development and function. Sex differences in adolescent stress-induced or exacerbated emotional and metabolic vulnerabilities could be due to sex-distinct gene expression in hypothalamic, limbic, and prefrontal brain regions. However, adolescent stress-induced whole-genome expression changes in key subregions of these brain regions were unclear. In this study, female and male adolescent Sprague Dawley rats received one-hour restraint stress daily from postnatal day (PD) 32 to PD44. Corticosterone levels, body weights, food intake, body composition, and circulating adiposity and sex hormones were measured. On PD44, brain and blood samples were collected. Using RNA-sequencing, sex-specific differences in stress-induced differentially expressed (DE) genes were identified in subregions of the hypothalamus, limbic system, and prefrontal cortex. Canonical pathways reflected well-known sex-distinct maladies and diseases, substantiating the therapeutic potential of the DE genes found in the current study. Thus, we proposed specific sex distinct, adolescent stress-induced transcriptional changes found in the current study as examples of the molecular bases for sex differences witnessed in stress induced or exacerbated emotional and metabolic disorders. Future behavioral studies and single-cell studies are warranted to test the implications of the DE genes identified in this study in sex-distinct stress-induced susceptibilities.

Formation of chronic morphine withdrawal memories requires C1QL3-mediated regulation of PSD95 in the mouse basolateral amygdala

Chronic morphine withdrawal memory formation is a complex process influenced by various molecular mechanisms. In this study, we aimed to investigate the contributions of the basolateral amygdala (BLA) and complement component 1, q subcomponent-like 3 (C1QL3), a secreted and presynaptically targeted protein, to the formation of chronic morphine (repeat dosing of morphine) withdrawal memory using conditioned place aversion (CPA) and chemogenetic methods. We conducted experiments involving the inhibition of the BLA during naloxone-induced withdrawal to assess its impact on CPA scores, providing insights into the significance of the BLA in the chronic morphine memory formation process. We also examined changes in C1ql3/C1QL3 expression within the BLA following conditioning. Immunofluorescence analysis revealed the colocalization of C1QL3 and the G protein-coupled receptor, brain-specific angiogenesis inhibitor 3 (BAI3) in the BLA, supporting their involvement in synaptic development. Moreover, we downregulated C1QL3 expression in the BLA to investigate its role in chronic morphine withdrawal memory formation. Our findings revealed that BLA inhibition during naloxone-induced withdrawal led to a significant reduction in CPA scores, confirming the critical role of the BLA in this memory process. Additionally, the upregulation of C1ql3 expression within the BLA postconditioning suggested its participation in withdrawal memory formation. The colocalization of C1QL3 and BAI3 in the BLA further supported their involvement in synaptic development. Furthermore, downregulation of C1QL3 in the BLA effectively hindered chronic morphine withdrawal memory formation, emphasizing its pivotal role in this process. Notably, we identified postsynaptic density protein 95 (PSD95) as a potential downstream effector of C1QL3 during chronic morphine withdrawal memory formation. Blocking PSD95 led to a significant reduction in the CPA score, and it appeared that C1QL3 modulated the ubiquitination-mediated degradation of PSD95, resulting in decreased PSD95 protein levels. This study underscores the importance of the BLA, C1QL3 and PSD95 in chronic morphine withdrawal memory formation. It provides valuable insights into the underlying molecular mechanisms, emphasizing their significance in this intricate process.

Daily fat intake is associated with basolateral amygdala response to high-calorie food cues and appetite for high-calorie food

OBJECTIVES

Animal studies have indicated that fat intake mediates amygdala activation, which in turn promotes fat intake, while amygdala activation increases the preference for fat and leads to increased fat intake. However, the association among fat intake, amygdala activation, and appetite for high-calorie foods in humans remains unclear. Thus, to examine this association, we conducted a functional magnetic resonance imaging (fMRI) experiment.

METHODS

Fifty healthy-weight adults (18 females; mean age: 22.9 ± 3.02 years) were included. Participants were shown images of high-calorie and low-calorie foods and were instructed to rate their desire to eat the food items during fMRI. All participants provided information on their daily fat intake using a self-reported questionnaire. Associations among fat intake, the desire to eat high-calorie or low-calorie food items, and amygdala responses to food items were examined.

RESULTS

The basolateral amygdala (BLA) response was positively associated with fat intake ([x, y, z] = [24, -6, -16], z = 3.91, pFWE-corrected = 0.007) and the desire to eat high-calorie food items ([26, -4, -16], z = 3.75, pFWE-corrected = 0.010). Structural equation modeling showed that the desire for high-calorie food items was predicted by BLA response to high-calorie food items (p = 0.013, β = 3.176), and BLA response was predicted by fat intake (p < 0.001, β = 0.026).

DISCUSSION

Fat intake influences BLA response to high-fat food, which in turn increases the desire to eat palatable high-fat food. This may lead to additional fat intake and increase the risk of weight gain.

BLA-involved circuits in neuropsychiatric disorders

The basolateral amygdala (BLA) is the subregion of the amygdala located in the medial of the temporal lobe, which is connected with a wide range of brain regions to achieve diverse functions. Recently, an increasing number of studies have focused on the participation of the BLA in many neuropsychiatric disorders from the neural circuit perspective, aided by the rapid development of viral tracing methods and increasingly specific neural modulation technologies. However, how to translate this circuit-level preclinical intervention into clinical treatment using noninvasive or minor invasive manipulations to benefit patients struggling with neuropsychiatric disorders is still an inevitable question to be considered. In this review, we summarized the role of BLA-involved circuits in neuropsychiatric disorders including Alzheimer's disease, perioperative neurocognitive disorders, schizophrenia, anxiety disorders, depressive disorders, posttraumatic stress disorders, autism spectrum disorders, and pain-associative affective states and cognitive dysfunctions. Additionally, we provide insights into future directions and challenges for clinical translation.

Immune and neural response to acute social stress in adolescent humans and rodents

Studies in adults have linked stress-related activation of the immune system to the manifestation of psychiatric conditions. Using a translational design, this study aimed to examine the impact of social stress on immune activity in adolescents and on neuronal activity in a preclinical mouse model. Participants were 31 adolescents (ages 12-19), including 25 with mood and anxiety symptoms. Whole-blood samples were collected before and after the Trier Social Stress Test (TSST), a stress-inducing public speaking task, then cultured for 6 hours in the presence and absence of the inflammatory endotoxin lipopolysaccharide (LPS). Effects of TSST and LPS on 41 immune biomarkers were examined using repeated-measures analysis of variance. Separately, juvenile (8-week-old) male mice were non-stressed or exposed to reminder social defeat then intraperitoneally injected with saline or LPS (n = 6/group). Brains were perfused and collected for immunohistochemistry and confocal microscopy at 0, 1, 6, and 24 hours post-injection. The activity was determined by the density of cFos-positive neurons in the paraventricular hypothalamus, paraventricular thalamus, and basolateral amygdala, regions known to show sustained activation to immunological challenge. Analyses in the adolescent study indicated a strong effect of LPS but no effects of TSST or TSST×LPS interaction on immune biomarkers. Similarly, reminder social defeat did not induce sustained neuronal activity changes comparable to LPS immunological challenge in juvenile mice. Our convergent findings across species suggest that the acute immune response to stress documented in adults is not present in youth. Thus, aging and chronicity effects may play an important role in the inflammatory response to acute psychosocial stress.

Cell- and Pathway-Specific Disruptions in the Accumbens of Fragile X Mouse

Fragile X syndrome (FXS) is a genetic cause of intellectual disability and autism spectrum disorder. The mesocorticolimbic system, which includes the prefrontal cortex (PFC), basolateral amygdala (BLA), and nucleus accumbens core (NAcC), is essential for regulating socioemotional behaviors. We employed optogenetics to compare the functional properties of the BLA→NAcC, PFC→NAcC, and reciprocal PFC↔BLA pathways in Fmr1-/y::Drd1a-tdTomato male mice. In FXS mice, the PFC↔BLA reciprocal pathway was unaffected, while significant synaptic modifications occurred in the BLA/PFC→NAcC pathways. We observed distinct changes in D1 striatal projection neurons (SPNs) and separate modifications in D2 SPNs. In FXS mice, the BLA/PFC→NAcC-D2 SPN pathways demonstrated heightened synaptic strength. Focusing on the BLA→NAcC pathway, linked to autistic symptoms, we found increased AMPAR and NMDAR currents and elevated spine density in D2 SPNs. Conversely, the amplified firing probability of BLA→NAcC-D1 SPNs was not accompanied by increased synaptic strength, AMPAR and NMDAR currents, or spine density. These pathway-specific alterations resulted in an overall enhancement of excitatory-to-spike coupling, a physiologically relevant index of how efficiently excitatory inputs drive neuronal firing, in both BLA→NAcC-D1 and BLA→NAcC-D2 pathways. Finally, the absence of fragile X messenger ribonucleoprotein 1 (FMRP) led to impaired long-term depression specifically in BLA→D1 SPNs. These distinct alterations in synaptic transmission and plasticity within circuits targeting the NAcC highlight the potential role of postsynaptic mechanisms in selected SPNs in the observed circuit-level changes. This research underscores the heightened vulnerability of the NAcC in the context of FMRP deficiency, emphasizing its pivotal role in the pathophysiology of FXS.

Dopamine Dysregulation in Reward and Autism Spectrum Disorder

Autism spectrum disorder (ASD) is primarily characterized by core deficits in social skills, communication, and cognition and by repetitive stereotyped behaviors. These manifestations are variable between individuals, and ASD pathogenesis is complex, with over a thousand implicated genes, many epigenetic factors, and multiple environmental influences. The mesolimbic dopamine (DA) mediated brain reward system is held to play a key role, but the rapidly expanding literature reveals intricate, nuanced signaling involving a wide array of mesolimbic loci, neurotransmitters and receptor subtypes, and neuronal variants. How altered DA signaling may constitute a downstream convergence of the manifold causal origins of ASD is not well understood. A clear working framework of ASD pathogenesis may help delineate common stages and potential diagnostic and interventional opportunities. Hence, we summarize the known natural history of ASD in the context of emerging data and perspectives to update ASD reward signaling. Then, against this backdrop, we proffer a provisional framework that organizes ASD pathogenesis into successive levels, including (1) genetic and epigenetic changes, (2) disrupted mesolimbic reward signaling pathways, (3) dysregulated neurotransmitter/DA signaling, and finally, (4) altered neurocognitive and social behavior and possible antagonist/agonist based ASD interventions. This subdivision of ASD into a logical progression of potentially addressable parts may help facilitate the rational formulation of diagnostics and targeted treatments.

Oral Fentanyl Consumption and Withdrawal Impairs Fear Extinction Learning and Enhances Basolateral Amygdala Principal Neuron Excitatory-Inhibitory Balance in Male and Female Mice

The number of opioid overdose deaths has increased over the past several years, mainly driven by an increase in the availability of highly potent synthetic opioids, like fentanyl, in the un-regulated drug supply. Over the last few years, changes in the drug supply, and in particular the availability of counterfeit pills containing fentanyl, have made oral use of opioids a more common route of administration. Here, we used a drinking in the dark (DiD) paradigm to model oral fentanyl self-administration using increasing fentanyl concentrations in male and female mice over 5 weeks. Fentanyl consumption peaked in both female and male mice at the 30 µg/mL dose, with female mice consuming significantly more fentanyl than male mice. Mice consumed sufficient fentanyl such that withdrawal was precipitated with naloxone, with males having more withdrawal symptoms, despite lower pharmacological exposure. We also performed behavioral assays to measure avoidance behavior and reward-seeking during fentanyl abstinence. Female mice displayed reduced avoidance behaviors in the open field assay, whereas male mice showed increased avoidance in the light/dark box assay. Female mice also exhibited increased reward-seeking in the sucrose preference test. Fentanyl-consuming mice of both sexes showed impaired cued fear extinction learning following fear conditioning and increased excitatory synaptic drive and increased excitability of BLA principal neurons. Our experiments demonstrate that long-term oral fentanyl consumption results in wide-ranging physiological and behavioral disruptions. This model could be useful to further study fentanyl withdrawal syndrome and behaviors and neuroplasticity associated with protracted fentanyl withdrawal.

Sex differences in acute early life stress-enhanced fear learning in adult rats

Patients diagnosed with posttraumatic stress disorder (PTSD) present with a spectrum of debilitating anxiety symptoms resulting from exposure to trauma. Women are twice as likely to be diagnosed with anxiety and PTSD compared to men; however, the reason for this vulnerability remains unknown. We conducted four experiments where we first demonstrated a female vulnerability to stress-enhanced fear learning (SEFL) with a moderate, acute early life stress (aELS) exposure (4 footshocks in a single session), compared to a more intense aELS exposure (15 footshocks in a single session) where males and females demonstrated comparable SEFL. Next, we demonstrated that this female vulnerability does not result from differences in footshock reactivity or contextual fear conditioning during the aELS exposure. Finally, using gonadectomy or sham surgeries in adult male and female rats, we showed that circulating levels of gonadal steroid hormones at the time of adult fear conditioning do not explain the female vulnerability to SEFL. Additional research is needed to determine whether this vulnerability can be explained by organizational effects of gonadal steroid hormones or differences in sex chromosome gene expression. Doing so is critical for a better understanding of increased female vulnerability to certain psychiatric diseases.

Inhibition of Protein Synthesis Attenuates Formation of Traumatic Memory and Normalizes Fear-Induced c-Fos Expression in a Mouse Model of Posttraumatic Stress Disorder

Posttraumatic stress disorder (PTSD) is a debilitating psychosomatic condition characterized by impairment of brain fear circuits and persistence of exceptionally strong associative memories resistant to extinction. In this study, we investigated the neural and behavioral consequences of inhibiting protein synthesis, a process known to suppress the formation of conventional aversive memories, in an established PTSD animal model based on contextual fear conditioning in mice. Control animals were subjected to the conventional fear conditioning task. Utilizing c-Fos neural activity mapping, we found that the retrieval of PTSD and normal aversive memories produced activation of an overlapping set of brain structures. However, several specific areas, such as the infralimbic cortex and the paraventricular thalamic nucleus, showed an increase in the PTSD group compared to the normal aversive memory group. Administration of protein synthesis inhibitor before PTSD induction disrupted the formation of traumatic memories, resulting in behavior that matched the behavior of mice with usual aversive memory. Concomitant with this behavioral shift was a normalization of brain c-Fos activation pattern matching the one observed in usual fear memory. Our findings demonstrate that inhibiting protein synthesis during traumatic experiences significantly impairs the development of PTSD in a mouse model. These data provide insights into the neural underpinnings of protein synthesis-dependent traumatic memory formation and open prospects for the development of new therapeutic strategies for PTSD prevention.

Exercise Influences the Brain's Metabolic Response to Chronic Cocaine Exposure in Male Rats

Cocaine use is associated with negative health outcomes: cocaine use disorders, speedballing, and overdose deaths. Currently, treatments for cocaine use disorders and overdose are non-existent when compared to opioid use disorders, and current standard cocaine use disorder treatments have high dropout and recidivism rates. Physical exercise has been shown to attenuate addiction behavior as well as modulate brain activity. This study examined the differential effects of chronic cocaine use between exercised and sedentary rats. The effects of exercise on brain glucose metabolism (BGluM) following chronic cocaine exposure were assessed using Positron Emission Tomography (PET) and [18F]-Fluorodeoxyglucose (FDG). Compared to sedentary animals, exercise decreased metabolism in the SIBF primary somatosensory cortex. Activation occurred in the amygdalopiriform and piriform cortex, trigeminothalamic tract, rhinal and perirhinal cortex, and visual cortex. BGluM changes may help ameliorate various aspects of cocaine abuse and reinstatement. Further investigation is needed into the underlying neuronal circuits involved in BGluM changes and their association with addiction behaviors.

Social isolation recruits amygdala-cortical circuitry to escalate alcohol drinking

How do social factors impact the brain and contribute to increased alcohol drinking? We found that social rank predicts alcohol drinking, where subordinates drink more than dominants. Furthermore, social isolation escalates alcohol drinking, particularly impacting subordinates who display a greater increase in alcohol drinking compared to dominants. Using cellular resolution calcium imaging, we show that the basolateral amygdala-medial prefrontal cortex (BLA-mPFC) circuit predicts alcohol drinking in a rank-dependent manner, unlike non-specific BLA activity. The BLA-mPFC circuit becomes hyperexcitable during social isolation, detecting social isolation states. Mimicking the observed increases in BLA-mPFC activity using optogenetics was sufficient to increase alcohol drinking, suggesting the BLA-mPFC circuit may be a neural substrate for the negative impact of social isolation. To test the hypothesis that the BLA-mPFC circuit conveys a signal induced by social isolation to motivate alcohol consumption, we first determined if this circuit detects social information. Leveraging optogenetics in combination with calcium imaging and computer vision pose tracking, we found that BLA-mPFC circuitry governs social behavior and neural representation of social contact. We further show that BLA-mPFC stimulation mimics social isolation-induced mPFC encoding of sucrose and alcohol, and inhibition of the BLA-mPFC circuit decreases alcohol drinking following social isolation. Collectively, these data suggest the amygdala-cortical circuit mirrors a neural encoding state similar to social isolation and underlies social isolation-associated alcohol drinking.

Potentiated GABAergic neuronal activities in the basolateral amygdala alleviate stress-induced depressive behaviors

AIMS

Major depressive disorder is a severe psychiatric disorder that afflicts ~17% of the world population. Neuroimaging investigations of depressed patients have consistently reported the dysfunction of the basolateral amygdala in the pathophysiology of depression. However, how the BLA and related circuits are implicated in the pathogenesis of depression is poorly understood.

METHODS

Here, we combined fiber photometry, immediate early gene expression (c-fos), optogenetics, chemogenetics, behavioral analysis, and viral tracing techniques to provide multiple lines of evidence of how the BLA neurons mediate depressive-like behavior.

RESULTS

We demonstrated that the aversive stimuli elevated the neuronal activity of the excitatory BLA neurons (BLACAMKII neurons). Optogenetic activation of CAMKII neurons facilitates the induction of depressive-like behavior while inhibition of these neurons alleviates the depressive-like behavior. Next, we found that the chemogenetic inhibition of GABAergic neurons in the BLA (BLAGABA ) increased the firing frequency of CAMKII neurons and mediates the depressive-like phenotypes. Finally, through fiber photometry recording and chemogenetic manipulation, we proved that the activation of BLAGABA neurons inhibits BLACAMKII neuronal activity and alleviates depressive-like behavior in the mice.

CONCLUSION

Thus, through evaluating BLAGABA and BLACAMKII neurons by distinct interaction, the BLA regulates depressive-like behavior.

Long-term calorie restriction prevented memory impairment in middle-aged male mice and increased a marker of DNA oxidative stress in hippocampal dentate gyrus

Calorie restriction (CR) is a non-invasive and economic approachknown to increase healthspan and life expectancy, through a decrease in oxidative stress, an increase in neurotrophins, among other benefits. However, it is not clear whether its benefit could be noted earlier, as at the beginning of middle-age. Hence, weaimed to determine whether six months of long-term CR, from early adulthood to the beginning of middle age (10 months of age) could positively affect cognitive, neurochemical, and behavioral parameters. Male C57BL6/J mice were randomly distributed into Young Control (YC, ad libitum food), Old Control (OC, ad libitum food), and Old Restricted (OR, 30 % of caloric restriction) groups. To analyze the cognitive and behavioral aspects, the novel object recognition task (NOR), open field, and elevated plus maze tests were performed. In addition, immunohistochemistry targetingΔFosB (neuronal activity), brain-derived neurotrophic factor (BDNF) and the DNA oxidative damage (8OHdG) in hippocampal subfields CA1, CA2, CA3, and dentate gyrus (DG), and in basolateral amygdala and striatum were performed. Our results showed that long-term CR prevented short-term memory impairment related to aging and increased 8OHdG in hippocampal DG. BDNF was not involved in the effects of either age or CR on memory at middle-age, as it increased in CA3 of the OC group but was not altered in OR. Regarding anxiety-type behavior, no parameter showed differences between the groups. In conclusion, while the effects of long-term CR on anxiety-type behavior were inconclusive, it mitigated the memory deficit related to aging, which was accompanied by an increase in hippocampal 8OHdG in DG. Future studies should investigate whether the benefits of CR would remain if the restriction were interrupted after this long-term protocol.

Neurometabolic profile of the amygdala in smokers assessed with 1H-magnetic resonance spectroscopy

Tobacco smoking is one of the main causes of premature death worldwide and quitting success remains low, highlighting the need to understand the neurobiological mechanisms underlying relapse. Preclinical models have shown that the amygdala and glutamate play an important role in nicotine addiction. The aims of this study were to compare glutamate and other metabolites in the amygdala between smokers and controls, and between different smoking states. Furthermore, associations between amygdalar metabolite levels and smoking characteristics were explored. A novel non-water-suppressed proton magnetic resonance spectroscopy protocol was applied to quantify neurometabolites in 28 male smokers (≥15 cigarettes/day) and 21 non-smoking controls, matched in age, education, verbal IQ, and weekly alcohol consumption. Controls were measured once (baseline) and smokers were measured in a baseline state (1-3 h abstinence), during withdrawal (24 h abstinence) and in a satiation state (directly after smoking). Baseline spectroscopy data were compared between groups by independent t-tests or Mann-Whitney-U tests. Smoking state differences were investigated by repeated-measures analyses of variance (ANOVAs). Associations between spectroscopy data and smoking characteristics were explored using Spearman correlations. Good spectral quality, high anatomical specificity (98% mean gray matter) and reliable quantification of most metabolites of interest were achieved in the amygdala. Metabolite levels did not differ between groups, but smokers showed significantly higher glutamine levels at baseline than satiation. Glx levels were negatively associated with pack-years and smoking duration. In summary, this study provides first insights into the neurometabolic profile of the amygdala in smokers with high anatomical specificity. By applying proton magnetic resonance spectroscopy, neurometabolites in smokers during different smoking states and non-smoking controls were quantified reliably. A significant shift in glutamine levels between smoking states was detected, with lower concentrations in satiation than baseline. The negative association between Glx levels and smoking quantity and duration may imply altered glutamate homeostasis with more severe nicotine addiction.

Lateralization of the 5-HT1A receptors in the basolateral amygdala in metabolic and anxiety responses to chronic restraint stress

Behavioral and functional studies describe hemispheric asymmetry in anxiety and metabolic behaviors in responses to stress. However, no study has reported serotonergic receptor (the 5-HT1A receptor) lateralization in the basolateral amygdala (BLA) in vivo on anxiety and metabolic behaviors under stress. In the present study, the effect of unilateral and bilateral suppression of the 5-HT1A receptor in the BLA on anxiety, and metabolic responses to chronic restraint stress was assessed. Male Wistar rats 7 days after cannulation into the BLA received chronic restraint stress for 14 consecutive days. 20 minutes before induction of stress, WAY-100-635 (selective 5-HT1A antagonist) or sterile saline (vehicle) was administered either uni- or bi-laterally into the BLA. Behavioral (elevated plus maze; EPM, and open field test), and metabolic parameter studies were performed. Results showed that stress causes a significant increase in weight gain compared to control. In the non-stress condition, the left and bilaterally, and in the stress condition the right, left, and both sides, inhibition of 5-HT1A in the BLA reduced weight gain. In the restraint stress condition, only inhibition of the 5-HT1A receptor in the left BLA led to decreased food intake compared to the control group. In stress conditions, inhibition of the 5-HT1A receptor on the right, left, and bilateral BLA increased water intake compared to the stress group. Inhibition of the 5-HT1A receptor on the left side of the BLA by WAY-100-635 induced anxiety-like behaviors in stressed rats. Similarly, WAY-100-635 on the left BLA effectively caused anxiety-like behaviors in both EPM and open field tests in the control animals. In conclusion, it seems that 5-HT1A receptors in the left BLA are more responsible for anxiety-like behaviors and metabolic changes in responses to stress.

Immune and Neural Response to Acute Social Stress in Adolescent Humans and Rodents

Studies in adults have linked stress-related activation of the immune system to the manifestation of psychiatric conditions. Using a translational design, this study aimed to examine the impact of social stress on immune activity in adolescents and on neuronal activity in a preclinical mouse model. Participants were 31 adolescents (ages 12-19), including 25 with mood and anxiety symptoms. Whole-blood samples were collected before and after the Trier Social Stress Test (TSST), a stress-inducing public speaking task, then cultured for 6 hours in the presence and absence of the inflammatory endotoxin lipopolysaccharide (LPS). Effects of TSST and LPS on 41 immune biomarkers were examined using repeated-measures analysis of variance. Separately, juvenile (8-week-old) male mice were non-stressed or exposed to reminder social defeat then intraperitoneally injected with saline or LPS (n = 6/group). Brains were perfused and collected for immunohistochemistry and confocal microscopy at 0, 1, 6, and 24 hours post-injection. Activity was determined by the density of cFos-positive neurons in the paraventricular hypothalamus, paraventricular thalamus, and basolateral amygdala, regions known to show sustained activation to immunological challenge. Analyses in the adolescent study indicated a strong effect of LPS but no effects of TSST or TSST×LPS interaction on immune biomarkers. Similarly, reminder social defeat did not induce sustained neuronal activity changes comparable to LPS immunological challenge in juvenile mice. Our convergent findings across species suggest that the acute immune response to stress documented in adults is not present in youth. Thus, aging and chronicity effects may play an important role in the inflammatory response to acute psychosocial stress.

Early life adversity drives sex-dependent changes in 5-mC DNA methylation of parvalbumin cells in the prefrontal cortex in rats

Early life adversity (ELA) can result in increased risk for developing affective disorders, such as anxiety or depression, later in life, with women showing increased risk. Interactions between an individual's genes and their environment play key roles in producing, as well as mitigating, later life neuropathology. Our current understanding of the underlying epigenomic drivers of ELA associated anxiety and depression are limited, and this stems in part from the complexity of underlying biochemical processes associated with how early experiences shapes later life behavior. Epigenetic alterations, or experience-driven modifications to DNA, can be leveraged to understand the interplay between genes and the environment. The present study characterized DNA methylation patterning, assessed via evaluation of 5-methylcytosine (5-mC), following ELA in a Sprague Dawley rat model of ELA induced by early caregiver deprivation. This study utilized maternal separation to investigate sex- and age-specific outcomes of ELA on epigenetic patterning in parvalbumin (PV)-containing interneurons in the prefrontal cortex (PFC), a subpopulation of inhibitory neurons which are associated with ELA and affective dysfunction. While global analysis of 5-mC methylation and CpG site specific pyrosequencing of the PV promoter, Pvalb, showed no obvious effects of ELA, when analyses were restricted to assessing 5-mC intensity in colocalized PV cells, there were significant sex and age dependent effects. We found that ELA leads sex-specific changes in PV cell counts, and that cell counts can be predicted by 5-mC intensity, with males and females showing distinct patterns of methylation and PV outcomes. ELA also produced sex-specific effects in corticosterone reactivity, with juvenile females showing a blunted stress hormone response compared to controls. Overall, ELA led to a sex-specific developmental shift in PV profile, which is comparable to profiles that are seen at a later developmental timepoint, and this shift may be mediated in part by epigenomic alterations driven by altered DNA methylation.

Overexpression of EphB2 in the basolateral amygdala is crucial for inducing visceral pain sensitization in rats subjected to water avoidance stress

AIMS

Basolateral amygdala (BLA), as a center for stress responses and emotional regulation, is involved in visceral hypersensitivity of irritable bowel syndrome (IBS) induced by stress. In the present study, we aimed to investigate the role of EphB2 receptor (EphB2) in BLA and explore the underlying mechanisms in this process.

METHODS

Visceral hypersensitivity was induced by water avoidance stress (WAS). Elevated plus maze test, forced swimming test, and sucrose preference test were applied to assess anxiety- and depression-like behaviors. Ibotenic acid or lentivirus was used to inactivate BLA in either the induction or maintenance stage of visceral hypersensitivity. The expression of protein was determined by quantitative PCR, immunofluorescence, and western blot.

RESULTS

EphB2 expression was increased in BLA in WAS rats. Inactivation of BLA or downregulation of EphB2 in BLA failed to induce visceral hypersensitivity as well as anxiety-like behaviors. However, during the maintenance stage of visceral pain, visceral hypersensitivity was only partially relieved but anxiety-like behaviors were abolished by inactivation of BLA or downregulation of EphB2 in BLA. Chronic WAS increased the expression of EphB2, N-methyl-D-aspartate receptors (NMDARs), and postsynaptic density protein (PSD95) in BLA. Downregulation of EphB2 in BLA reduced NMDARs and PSD95 expression in WAS rats. However, activation of NMDARs after the knockdown of EphB2 expression still triggered visceral hypersensitivity and anxiety-like behaviors.

CONCLUSIONS

Taken together, the results suggest that EphB2 in BLA plays an essential role in inducing visceral hypersensitivity. In the maintenance stage, the involvement of EphB2 is crucial but not sufficient. The increase in EphB2 induced by WAS may enhance synaptic plasticity in BLA through upregulating NMDARs, which results in IBS-like symptoms. These findings may give insight into the treatment of IBS and related psychological distress.

Oxytocin neurons mediate stress-induced social memory impairment

Oxytocin has long been thought to play a substantial role in social behaviors, such as social attachment and parenting behavior. However, how oxytocin neurons respond to social and non-social stimuli is largely unknown, especially in high temporal resolution. Here, we recorded the in vivo real-time responses of oxytocin neurons in the paraventricular nucleus of the hypothalamus (PVN) in freely behaving mice. Our results revealed that oxytocin neurons were activated more significantly by stressors than social stimuli. The activation of oxytocin neurons was precisely correlated with struggling behavior during stress. Furthermore, we found that oxytocin mediated stress-induced social memory impairment. Our results reveal an important role of PVN oxytocin neurons in stress-induced social amnesia.

Altered amygdala volumes and microstructure in focal epilepsy patients with tonic-clonic seizures, ictal, and post-convulsive central apnea

OBJECTIVES

Sudden unexpected death in epilepsy (SUDEP) is a leading cause of death for patients with epilepsy; however, the pathophysiology remains unclear. Focal-to-bilateral tonic-clonic seizures (FBTCS) are a major risk factor, and centrally-mediated respiratory depression may increase the risk further. Here, we determined the volume and microstructure of the amygdala, a key structure that can trigger apnea in people with focal epilepsy, stratified by the presence or absence of FBTCS, ictal central apnea (ICA), and post-convulsive central apnea (PCCA).

METHODS

Seventy-three patients with focal impaired awareness seizures without FBTC seizures (FBTCneg group) and 30 with FBTCS (FBTCpos group) recorded during video electroencephalography (VEEG) with respiratory monitoring were recruited prospectively during presurgical investigations. We acquired high-resolution T1-weighted anatomic and multi-shell diffusion images, and computed neurite orientation dispersion and density imaging (NODDI) metrics in all patients with epilepsy and 69 healthy controls. Amygdala volumetric and microstructure alterations were compared between three groups: healthy subjects, FBTCneg and FBTCpos groups. The FBTCpos group was further subdivided by the presence of ICA and PCCA, verified by VEEG.

RESULTS

Bilateral amygdala volumes were significantly increased in the FBTCpos cohort compared to healthy controls and the FBTCneg group. Patients with recorded PCCA had the highest increase in bilateral amygdala volume of the FBTCpos cohort. Amygdala neurite density index (NDI) values were decreased significantly in both the FBTCneg and FBTCpos groups relative to healthy controls, with values in the FBTCpos group being the lowest of the two. The presence of PCCA was associated with significantly lower NDI values vs the non-apnea FBTCpos group (p = 0.004).

SIGNIFICANCE

Individuals with FBTCpos and PCCA show significantly increased amygdala volumes and disrupted architecture bilaterally, with greater changes on the left side. The structural alterations reflected by NODDI and volume differences may be associated with inappropriate cardiorespiratory patterns mediated by the amygdala, particularly after FBTCS. Determination of amygdala volumetric and architectural changes may assist identification of individuals at risk.

Emotion in action: When emotions meet motor circuits

The brain is a remarkably complex organ responsible for a wide range of functions, including the modulation of emotional states and movement. Neuronal circuits are believed to play a crucial role in integrating sensory, cognitive, and emotional information to ultimately guide motor behavior. Over the years, numerous studies employing diverse techniques such as electrophysiology, imaging, and optogenetics have revealed a complex network of neural circuits involved in the regulation of emotional or motor processes. Emotions can exert a substantial influence on motor performance, encompassing both everyday activities and pathological conditions. The aim of this review is to explore how emotional states can shape movements by connecting the neural circuits for emotional processing to motor neural circuits. We first provide a comprehensive overview of the impact of different emotional states on motor control in humans and rodents. In line with behavioral studies, we set out to identify emotion-related structures capable of modulating motor output, behaviorally and anatomically. Neuronal circuits involved in emotional processing are extensively connected to the motor system. These circuits can drive emotional behavior, essential for survival, but can also continuously shape ongoing movement. In summary, the investigation of the intricate relationship between emotion and movement offers valuable insights into human behavior, including opportunities to enhance performance, and holds promise for improving mental and physical health. This review integrates findings from multiple scientific approaches, including anatomical tracing, circuit-based dissection, and behavioral studies, conducted in both animal and human subjects. By incorporating these different methodologies, we aim to present a comprehensive overview of the current understanding of the emotional modulation of movement in both physiological and pathological conditions.

Recent advances in anxiety disorders: Focus on animal models and pathological mechanisms

Anxiety disorders have become one of the most severe psychiatric disorders, and the incidence is increasing every year. They impose an extraordinary personal and socioeconomic burden. Anxiety disorders are influenced by multiple complex and interacting genetic, psychological, social, and environmental factors, which contribute to disruption or imbalance in homeostasis and eventually cause pathologic anxiety. The selection of a suitable animal model is important for the exploration of disease etiology and pathophysiology, and the development of new drugs. Therefore, a more comprehensive understanding of the advantages and limitations of existing animal models of anxiety disorders is helpful to further study the underlying pathological mechanisms of the disease. This review summarizes animal models and the pathogenesis of anxiety disorders, and discusses the current research status to provide insights for further study of anxiety disorders.

Neurogenetics and Epigenetics of Loneliness

Loneliness, an established risk factor for both, mental and physical morbidity, is a mounting public health concern. However, the neurobiological mechanisms underlying loneliness-related morbidity are not yet well defined. Here we examined the role of genes and associated DNA risk polymorphic variants that are implicated in loneliness via genetic and epigenetic mechanisms and may thus point to specific therapeutic targets. Searches were conducted on PubMed, Medline, and EMBASE databases using specific Medical Subject Headings terms such as loneliness and genes, neuro- and epigenetics, addiction, affective disorders, alcohol, anti-reward, anxiety, depression, dopamine, cancer, cardiovascular, cognitive, hypodopaminergia, medical, motivation, (neuro)psychopathology, social isolation, and reward deficiency. The narrative literature review yielded recursive collections of scientific and clinical evidence, which were subsequently condensed and summarized in the following key areas: (1) Genetic Antecedents: Exploration of multiple genes mediating reward, stress, immunity and other important vital functions; (2) Genes and Mental Health: Examination of genes linked to personality traits and mental illnesses providing insights into the intricate network of interaction converging on the experience of loneliness; (3) Epigenetic Effects: Inquiry into instances of loneliness and social isolation that are driven by epigenetic methylations associated with negative childhood experiences; and (4) Neural Correlates: Analysis of loneliness-related affective states and cognitions with a focus on hypodopaminergic reward deficiency arising in the context of early life stress, eg, maternal separation, underscoring the importance of parental support early in life. Identification of the individual contributions by various (epi)genetic factors presents opportunities for the creation of innovative preventive, diagnostic, and therapeutic approaches for individuals who cope with persistent feelings of loneliness. The clinical facets and therapeutic prospects associated with the current understanding of loneliness, are discussed emphasizing the relevance of genes and DNA risk polymorphic variants in the context of loneliness-related morbidity.

Nature-based biopsychosocial resilience: An integrative theoretical framework for research on nature and health

Nature-based solutions including urban forests and wetlands can help communities cope better with climate change and other environmental stressors by enhancing social-ecological resilience. Natural ecosystems, settings, elements and affordances can also help individuals become more personally resilient to a variety of stressors, although the mechanisms underpinning individual-level nature-based resilience, and their relations to social-ecological resilience, are not well articulated. We propose 'nature-based biopsychosocial resilience theory' (NBRT) to address these gaps. Our framework begins by suggesting that individual-level resilience can refer to both: a) a person's set of adaptive resources; and b) the processes by which these resources are deployed. Drawing on existing nature-health perspectives, we argue that nature contact can support individuals build and maintain biological, psychological, and social (i.e. biopsychosocial) resilience-related resources. Together with nature-based social-ecological resilience, these biopsychosocial resilience resources can: i) reduce the risk of various stressors (preventive resilience); ii) enhance adaptive reactions to stressful circumstances (response resilience), and/or iii) facilitate more rapid and/or complete recovery from stress (recovery resilience). Reference to these three resilience processes supports integration across more familiar pathways involving harm reduction, capacity building, and restoration. Evidence in support of the theory, potential interventions to promote nature-based biopsychosocial resilience, and issues that require further consideration are discussed.

Gestational intermittent hypoxia increases FosB-immunoreactive perikaryas in the paraventricular nucleus of the hypothalamus of adult male (but not female) rats

Sleep-disordered breathing is a respiratory disorder commonly experienced by pregnant women. The recurrent hypoxaemic events associated with sleep-disordered breathing have deleterious consequences for the mother and fetus. Adult male (but not female) rats born to dams subjected to gestational intermittent hypoxia (GIH) have a higher resting blood pressure than control animals and show behavioural/neurodevelopmental disorders. The origin of this persistent, sex-specific effect of GIH in offspring is unknown, but disruption of the neuroendocrine stress pathways is a key mechanism by which gestational stress increases disease risk in progeny. Using FosB immunolabelling as a chronic marker of neuronal activation, we determined whether GIH augments basal expression of FosB in the perikaryas of cells in the paraventricular nucleus of the hypothalamus (PVN), a key structure in the regulation of the stress response and blood pressure. From gestational day 10, female rats were subjected to GIH for 8 h/day (light phase) until the day before delivery (gestational day 21); GIH consisted of 2 min hypoxic bouts (10.5% O2 ) alternating with normoxia. Control rats were exposed to intermittent normoxia over the same period (GNX). At adulthood (10-15 weeks), the brains of male and female rats were harvested for FosB immunohistochemistry. In males, GIH augmented PVN FosB labelling density by 30%. Conversely, PVN FosB density in GIH females was 28% lower than that of GNX females. We conclude that GIH has persistent and sex-specific impacts on the development of stress pathways, thereby offering a plausible mechanism by which GIH can disturb neural development and blood pressure homeostasis in adulthood. NEW FINDINGS: What is the central question of this study? In pregnant women, sleep apnoea increases the risk of disease for the offspring at various life stages. Given that gestational stress disrupts the programming of the stress pathways, we determined whether exposing female rats to gestational intermittent hypoxia (GIH) activates hypothalamic neurons regulating the stress response in adult rats. What is the main finding and its importance? Using FosB immunolabelling as a marker of marker of neuronal activation, we showed that GIH augmented basal activation of the paraventricular nucleus of the hypothalamus in males, but not females. Disruption of the stress pathways is a new hypothesis to explain the persistent and sex-specific impacts of GIH on offspring health.

Disrupting astrocyte-neuron lactate transport prevents cocaine seeking after prolonged withdrawal

Energy supply, especially the transfer of lactate from astrocytes to neurons, is critical for neuronal plasticity. However, its role in the incubation of cocaine craving remains largely unknown. Using an extended-access self-administration model and in vivo 1H-magnetic resonance spectroscopy, we found that lactate synthesis in the central amygdala (CeA) is required for the intensified cocaine craving after prolonged withdrawal. Furthermore, incubated cocaine seeking was associated with a selective increase in monocarboxylate transporter 2 (MCT2) and MCT4 expression levels. Down-regulation of astrocytic MCT4 or neuronal MCT2 using targeted antisense oligonucleotides or cell type-specific shRNA attenuated cocaine craving and reduced the expression of plasticity-related proteins and excitatory synaptic transmission. Meanwhile, lactate administration rescued MCT4 but not MCT2 disruption-induced behavioral changes due to the inability of lactate to be transported into neurons. Together, our study highlights the critical role of astrocyte-neuron lactate transport in the CeA in the incubation of cocaine craving and suggests a potential therapeutic target for drug addiction.

Physiological and cognitive changes after treatments of cyclophosphamide, methotrexate, and fluorouracil: implications of the gut microbiome and depressive-like behavior

Introduction

Chemotherapy-induced cognitive impairment colloquially referred to as chemobrain is a poorly understood phenomenon affecting a highly variable proportion of patients with breast cancer. Here we investigate the association between anxiety and despair-like behaviors in mice treated with cyclophosphamide, methotrexate, and fluorouracil (CMF) along with host histological, proteomic, gene expression, and gut microbial responses.

Methods

Forced swim and sociability tests were used to evaluate depression and despair-like behaviors. The tandem mass tag (TMT) proteomics approach was used to assess changes in the neural protein network of the amygdala and hippocampus. The composition of gut microbiota was assessed through 16S rRNA gene sequencing. Finally, quantitative reverse transcription polymerase chain reaction (qRT-PCR) was used to evaluate changes in intestinal gap junction markers.

Results and discussion

We observed that CMF induced social and despair-like behavior in mice 96 hours following treatment. Proteomic analysis identified changes in various proteins related to progressive neurological disease, working memory deficit, primary anxiety disorder, and gene expression revealing increases in NMDA and AMPA receptors in both the hippocampus and the amygdala because of CMF treatment. These changes finally, we observed immediate changes in the microbial population after chemotherapy treatment, with a notable abundance of Muribaculaceae and Romboutsia which may contribute to changes seen in the gut.

Brain responses to positive and negative events in individuals with internet gaming disorder during real gaming

Objective

This study sought to investigate brain responses to positive and negative events in individuals with internet gaming disorder (IGD) during real gaming as a direct assessment of the neural features of IGD. This investigation reflects the neural deficits in individuals with IGD while playing games, providing direct and effective targets for prevention and treatment of IGD.

Methods

Thirty subjects with IGD and fifty-two matched recreational game use (RGU) subjects were scanned while playing an online game. Abnormal brain activities during positive and negative events were detected using a general linear model. Functional connectivity (FC) and correlation analyses between neural features and addiction severity were conducted to provide additional support for the underlying neural features.

Results

Compared to the RGU subjects, the IGD subjects exhibited decreased activation in the dorsolateral prefrontal cortex (DLPFC) during positive events and decreased activation in the middle frontal gyrus (MFG), precentral gyrus and postcentral gyrus during negative events. Decreased FC between the DLPFC and putamen during positive events and between the MFG and amygdala during negative events were observed among the IGD subjects. Neural features and addiction severity were significantly correlated.

Conclusions

Individuals with IGD exhibited deficits in regulating game craving, maladaptive habitual gaming behaviors and negative emotions when experiencing positive and negative events during real game-playing compared to RGU gamers. These abnormalities in neural substrates during real gaming provide direct evidence for explaining why individuals with IGD uncontrollably and continuously engage in game playing, despite negative consequences.

Early life stress impairs VTA coordination of BLA network and behavioral states

Motivated behaviors, such as social interactions, are governed by the interplay between mesocorticolimbic structures, such as the ventral tegmental area (VTA), basolateral amygdala (BLA), and medial prefrontal cortex (mPFC). Adverse childhood experiences and early life stress (ELS) can impact these networks and behaviors, which is associated with increased risk for psychiatric illnesses. While it is known that the VTA projects to both the BLA and mPFC, the influence of these inputs on local network activity which govern behavioral states - and whether ELS impacts VTA-mediated network communication - remains unknown. Our study demonstrates that VTA inputs influence BLA oscillations and mPFC activity, and that ELS weakens the ability of the VTA to coordinate BLA network states, likely due to ELS-induced impairments in dopamine signaling between the VTA and BLA. Consequently, ELS mice exhibit increased social avoidance, which can be recapitulated in control mice by inhibiting VTA-BLA communication. These data suggest that ELS impacts social reward via the VTA-BLA dopamine network.

Pharmacological activation of the amygdala, but not single prolonged footshock-induced acute stress, interferes with cue-induced motivation toward food rewards in rats

In the face of threats, animals adapt their behaviors to cope with the situation. Under such circumstances, irrelevant behaviors are usually suppressed. In this study, we examined whether food-seeking motivation would decrease under activation of the amygdala, an important nucleus in the regulation of stress response in the central nervous system, or after a physical acute stress session. In Experiment 1, we pharmacologically activated the basolateral nucleus (BLA) or the central nucleus of the amygdala (CeA) before a cue-induced reinstatement test in rats. Our results showed that activation of the BLA or the CeA abolished cue-induced motivation toward food rewards, while locomotor activity and free food intake were not affected. In Experiments 2 and 3, we further assessed anxiety and despair levels, as well as cue-induced reinstatement, after a single prolonged footshock-induced acute stress in rats. Behaviorally, acute stress did not affect anxiety level, despair level, or cue-induced motivation toward food rewards. Physiologically, there was no difference in cellular activities of the amygdala immediately after acute stress. To conclude, our results suggested that pharmacological activation of the amygdala decreased cue-induced motivation toward food reward. However, physiological acute stress did not immediately interfere with the negative emotions, motivation, or amygdala activities of the animals.

The excitatory transmission from basolateral nuclues of amygdala to nucleus accumbens shell regulates propofol self-administration through AMPA receptors

Propofol addictive properties have been demonstrated in humans and rats. The glutamatergic transmission from basolateral nucleus of amygdala (BLA) to the nucleus accumbens (NAc) modulates reward-seeking behaviour; especially, NAc shell (NAsh) is implicated in reward-seeking response. Previous studies indicated the interactions between AMPA receptors (AMPARs) and dopamine D1 receptor (D1R) in NAc mediated drug addiction, but whether the circuit of BLA-to-NAsh and AMPARs regulate propofol addiction remains unclear. We trained adult male Sprague-Dawley rats for propofol self-administration to examine the changes of action potentials (APs) and spontaneous excitatory postsynaptic currents (sEPSCs) in the NAsh. Thereafter, optogenetic stimulation with adeno-associated viral vectors microinjections in BLA was used to explore the effect of BLA-to-NAsh on propofol self-administration behaviour (1.7 mg/kg/injection). The pretreatment effects with NBQX (0.25-1.0 μg/0.3 μl/site) or vehicle in the NAsh on propofol self-administration behaviour, the expressions of AMPARs subunits and D1R/ERK/CREB signalling pathway in the NAc were detected. The results showed that the number of APs, amplitude and frequency of sEPSCs were enhanced in propofol self-administrated rats. Propofol self-administration was inhibited in the NpHR3.0-EYFP group, but in the ChR2-EYFP group, there was a promoting effect, which could be weakened by NBQX pretreatment. NBQX pretreatment also significantly decreased the expressions of GluA2 subunit and D1R in the NAc but did not change the expressions of GluA1 and ERK/CREB signalling pathway. The evidence supports a vital role of BLA-to-NAsh circuit in regulating propofol self-administration and suggests this central reward processing may function through the interaction between AMPARs and D1R in the NAsh.

A prolonged stress rat model recapitulates some PTSD-like changes in sleep and neuronal connectivity

Chronic post-traumatic stress disorder (PTSD) exhibits psychological abnormalities during fear memory processing in rodent models. To simulate long-term impaired fear extinction in PTSD patients, we constructed a seven-day model with multiple prolonged stress (MPS) by modifying manipulation repetitions, intensity, and unpredictability of stressors. Behavioral and neural changes following MPS conveyed longitudinal PTSD-like effects in rats for 6 weeks. Extended fear memory was estimated through fear retrieval induced-freezing behavior and increased long-term serum corticosterone concentrations after MPS manipulation. Additionally, memory retrieval and behavioral anxiety tasks continued enhancing theta oscillation activity in the prefrontal cortex-basal lateral amygdala-ventral hippocampus pathway for an extended period. Moreover, MPS and remote fear retrieval stimuli disrupted sleep-wake activities to consolidate fear memory. Our prolonged fear memory, neuronal connectivity, anxiety, and sleep alteration results demonstrated integrated chronic PTSD symptoms in an MPS-induced rodent model.

[Anxiety and substance abuse disorders-Focus on alcohol and cannabis]

Anxiety disorders are frequent, with a 12-month prevalence of 14%, tend to be chronic, and display a high comorbidity with substance abuse disorders. Anxiety and substance abuse disorders are associated with a pronounced individual as well as socioeconomic burden. This article reviews the epidemiological, etiological, and clinical aspects of the dual diagnosis of anxiety and substance abuse disorders, with a particular focus on alcohol and cannabis. The treatment comprises nonpharmacological strategies, mainly cognitive behavioral therapy combined with elements of motivational interviewing (MI) and pharmacological management with antidepressants; however, the use of selective serotonin reuptake inhibitors (SSRI)/serotonin and noradrenaline reuptake inhibitors (SNRI) is not unreservedly recommended. The use of gabapentinoids requires careful risk-benefit consideration because of their potential for abuse and dependence in substance abuse disorders. Benzodiazepines are reserved exclusively for crisis management. Rapid diagnosis and treatment initiation targeting both disorders are essential for successful treatment of comorbid anxiety and substance abuse disorders.

Cocaine Exposure Increases Excitatory Synaptic Transmission and Intrinsic Excitability in the Basolateral Amygdala in Male and Female Rats and across the Estrous Cycle

INTRODUCTION

Sex and ovarian hormones influence cocaine seeking and relapse vulnerability, but less is known regarding the cellular and synaptic mechanisms contributing to these behavioral sex differences. One factor thought to influence cue-induced seeking behavior following withdrawal is cocaine-induced changes in the spontaneous activity of pyramidal neurons in the basolateral amygdala (BLA). However, the mechanisms underlying these changes, including potential sex or estrous cycle effects, are unknown.

METHODS

Ex vivo whole-cell patch clamp electrophysiology was conducted to investigate the effects of cocaine exposure, sex, and estrous cycle fluctuations on two properties that can influence spontaneous activity of BLA pyramidal neurons: (1) frequency and amplitude of spontaneous excitatory postsynaptic currents (sEPSCs) and (2) intrinsic excitability. Recordings of BLA pyramidal neurons were conducted in adult male and female rats and across the estrous cycle following 2-4 weeks of withdrawal from extended-access cocaine self-administration (6 h/day for 10 days) or drug-naïve conditions.

RESULTS

In both sexes, cocaine exposure increased the frequency, but not amplitude, of sEPSCs and neuronal intrinsic excitability. Across the estrous cycle, sEPSC frequency and intrinsic excitability were significantly elevated only in cocaine-exposed females in the estrus stage of the cycle, a stage when cocaine-seeking behavior is known to be enhanced.

CONCLUSIONS

Here, we identify potential mechanisms underlying cocaine-induced alterations in the spontaneous activity of BLA pyramidal neurons in both sexes along with changes in these properties across the estrous cycle.

Dose mediates the protracted effects of adolescent THC exposure on reward and stress reactivity in males relevant to perturbation of the basolateral amygdala transcriptome

Despite the belief that cannabis is relatively harmless, exposure during adolescence is associated with increased risk of developing several psychopathologies in adulthood. In addition to the high levels of use amongst teenagers, the potency of ∆-9-tetrahydrocannabinol (THC) has increased more than fourfold compared to even twenty years ago, and it is unclear whether potency influences the presentation of THC-induced behaviors. Expanded knowledge about the impact of adolescent THC exposure, especially high dose, is important to delineating neural networks and molecular mechanisms underlying psychiatric risk. Here, we observed that repeated exposure to low (1.5 mg/kg) and high (5 mg/kg) doses of THC during adolescence in male rats produced divergent effects on behavior in adulthood. Whereas low dose rats showed greater sensitivity to reward devaluation and also self-administered more heroin, high dose animals were significantly more reactive to social isolation stress. RNA sequencing of the basolateral amygdala, a region linked to reward processing and stress, revealed significant perturbations in transcripts and gene networks related to synaptic plasticity and HPA axis that were distinct to THC dose as well as stress. In silico single-cell deconvolution of the RNAseq data revealed a significant reduction of astrocyte-specific genes related to glutamate regulation in stressed high dose animals, a result paired anatomically with greater astrocyte-to-neuron ratios and hypotrophic astrocytes. These findings emphasize the importance of dose and behavioral state on the presentation of THC-related behavioral phenotypes in adulthood and dysregulation of astrocytes as an interface for the protracted effects of high dose THC and subsequent stress sensitivity.

Cannabidiol Differentially Modulates Synaptic Release and Cellular Excitability in Amygdala Subnuclei

Cannabidiol (CBD) is a non-psychoactive constituent of the Cannabis plant that has purported effectiveness in treating an array of stress-related neuropsychiatric disorders. The amygdala is a subcortical brain structure that regulates emotional behavior, and its dysfunction has been linked to numerous disorders including anxiety and posttraumatic stress disorder. Despite this, the direct effects of CBD on synaptic and cellular function in the amygdala are not known. Using electrophysiology and pharmacology, we report that CBD reduces presynaptic neurotransmitter release in the amygdala, and these effects are dependent on subnucleus and cell type. Furthermore, CBD broadly decreases cellular excitability across amygdala subnuclei. These data reveal physiological mechanisms by which CBD modulates amygdala activity and could provide insights into how CBD could affect emotional and stress-related behavioral responses.

5-HT1B receptors in the basolateral amygdaloid nucleus regulate anxiety-like behaviors through AC-PKA signal pathway in a rat model of Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is commonly accompanied with anxiety, multiple studies indicate that the basolateral amygdaloid nucleus (BLA) is closely related to modulation of anxiety and expresses serotonin_1B (5-HT_1B) receptors, however, effects of BLA 5-HT_1B receptors on anxiety-like behaviors are unclear, particularly in PD-related anxiety.

METHODS

The open-field and elevated plus maze tests were used to examine anxiety-like behaviors. In vivo electrophysiology and microdialysis were performed to observe the firing activity of BLA neurons and GABA, glutamate, dopamine (DA) and 5-HT release in the BLA, respectively. Western blotting was used to analyze protein expression of 5-HT_1B receptors, adenylate cyclase (AC) and phosphorylated protein kinase A at threonine 197 site (p-PKA-Thr197) in the BLA.

RESULTS

Intra-BLA injection of 5-HT_1B receptor agonist CP93129 produced anxiety-like effects and antagonist SB216641 induced anxiolytic-like responses in sham-operated and 6-hydroxydopamine-lesioned rats. Further, pretreatment with AC inhibitor SQ22536 and PKA inhibitor KT5720 blocked the behavioral effects of CP93129, respectively. Intra-BLA injection of CP93129 increased the firing rate of BLA glutamate neurons and decreased GABA/glutamate ratio and DA and 5-HT levels in the BLA of sham-operated and the lesioned rats, while SB216641 induced the opposite effects. Compared with sham-operated rats, effects of CP93129 and SB216641 on behaviors, electrophysiology and microdialysis were decreased in the lesioned rats, which were associated with decreased expression of 5-HT_1B receptors, AC and p-PKA-Thr197 in the BLA.

CONCLUSION

These findings suggest that 5-HT_1B receptor-AC-PKA signal pathway in the BLA is involved in the regulation of PD-related anxiety.

INVOLVEMENT OF CORTICAL PROJECTIONS TO BASOLATERAL AMYGDALA IN CONTEXT-INDUCED REINSTATEMENT OF ETHANOL-SEEKING IN RATS

Ethanol is the most consumed substance of abuse in the world, and its misuse may lead to the development of alcohol use disorder (AUD). High relapse rates remain a relevant problem in the treatment of AUD. Exposure to environmental cues previously associated with ethanol intake could trigger ethanol-seeking behavior. However, the neural mechanisms involved in this phenomenon are not entirely clear. In this context, cortical projections to the basolateral amygdala (BLA) play a role in appetitive and aversive learned behaviors. Therefore, we aimed to evaluate the activation of the cortical projections from the prelimbic (PL), orbitofrontal (OFC), and infralimbic (IL), to the BLA in the context-induced reinstatement of ethanol-seeking. Male Long-Evans rats were trained to self-administer 10% ethanol in Context A. Subsequently, lever pressing in the presence of the discrete cue was extinguished in Context B. After nine extinction sessions, rats underwent intracranial surgery for the unilateral injection of red fluorescent retrograde tracer into the BLA. The context-induced reinstatement of ethanol-seeking was assessed by re-exposing the rats to Context A or B under extinction conditions. Finally, we combined retrograde neuronal tracing with Fos to identify activated cortical inputs to BLA during the reinstatement of ethanol-seeking behavior. We found that PL, but not OFC or IL, retrogradely-labeled neurons from BLA presented increased Fos expression during the re-exposure to the ethanol-associated context, suggesting that PL projection to BLA is involved in the context-induced reinstatement of ethanol-seeking behavior.