Adaptations in glutathione-based redox protein signaling pathways and alcohol drinking across species.

Alcohol use disorder (AUD) is the most prevalent substance use disorder but there is incomplete knowledge of the underlying molecular etiology. Here, we examined the cytosolic proteome from the nucleus accumbens core (NAcC) of ethanol drinking rhesus macaques to identify ethanol-sensitive signaling proteins. The targets were subsequently investigated using bioinformatics, genetic, and pharmacological manipulations in mouse models of ethanol drinking. Of the 1000+ cytosolic proteins identified in our screen, 50 proteins differed significantly between control and ethanol drinking macaques. Gene Ontology analysis of the differentially expressed proteins identified enrichment in pathways regulating metabolic processes and proteasome activity. Because the family of Glutathione S-transferases (GSTs) was enriched in these pathways, validation studies targeted GSTs using bioinformatics and genetically diverse mouse models. Gstp1 and Gstm2 were identified in Quantitative Trait Loci and published gene sets for ethanol-related phenotypes (e.g., ethanol preference, conditioned taste aversion, differential expression), and recombinant inbred strains that inherited the C57BL/6J allele at the Gstp2 interval consumed higher amounts of ethanol than those that inherited the DBA/2J allele. Genetic deletion of Gstp1/2 led to increased ethanol consumption without altering ethanol metabolism or sucrose preference. Administration of the pharmacologic activator of Gstp1/2, carnosic acid, decreased voluntary ethanol drinking. Proteomic analysis of the NAcC cytosolic of heavy drinking macaques that were validated in mouse models indicate a role for glutathione-mediated redox regulation in ethanol-related neurobiology and the potential of pharmacological interventions targeting this system to modify excessive ethanol drinking.

Astrocytic CREB in nucleus accumbens promotes susceptibility to chronic stress.

BACKGROUND: Increasing evidence implicates astrocytes in stress and depression in both rodent models and human Major Depressive Disorder (MDD). Despite this, little is known about the transcriptional responses to stress of astrocytes within the nucleus accumbens (NAc), a key brain reward region, and their influence on behavioral outcomes. METHODS: We used whole cell sorting, RNA-sequencing, and bioinformatic analyses to investigate the NAc astrocyte transcriptome in male mice in response to chronic social defeat stress (CSDS). Immunohistochemistry was used to determine stress-induced changes in astrocytic CREB within the NAc. Finally, astrocytic regulation of depression-like behavior was investigated using viral-mediated manipulation of CREB in combination with CSDS. RESULTS: We found a robust transcriptional response in NAc astrocytes to CSDS in stressed mice, with changes seen in both stress-susceptible and stress-resilient animals. Bioinformatic analysis revealed CREB, a transcription factor widely studied in neurons, as one of the top-predicted upstream regulators of the NAc astrocyte transcriptome, with opposite activation states implicated in resilient vs. susceptible mice. This bioinformatic deduction was confirmed at the protein level with immunohistochemistry. Moreover, NAc astrocyte morphological complexity correlated with CREB activation and was reduced selectively in astrocytes of resilient mice. Viral overexpression of CREB selectively in NAc astrocytes promoted susceptibility to chronic stress. CONCLUSIONS: Together, our data demonstrate that the astrocyte transcriptome responds robustly to CSDS and that transcriptional regulation in astrocytes contributes to depressive-like behaviors. A better understanding of transcriptional regulation in astrocytes may reveal unknown molecular mechanisms underlying neuropsychiatric disorders.

Basolateral amygdala inputs to the nucleus accumbens shell modulate the consolidation of cued-response and inhibitory avoidance learning.

The basolateral amygdala (BLA) modulates different types of memory consolidation via distinct projections to downstream brain regions in multiple memory systems. Prior studies indicate that the BLA projects to the nucleus accumbens shell (NAshell) and that these regions interact to influence some types of behavior. Moreover, previous pharmacological work suggests the BLA and NAshell interact to influence memory. However, the precise role of the BLA-NAshell pathway has never been directly investigated in the consolidation of different types of memory including cued-response, spatial, or inhibitory avoidance (IA) learning. To address this, male and female Sprague-Dawley rats received optogenetic manipulations of the BLA or BLA-NAshell pathway immediately following training in different learning tasks. An initial experiment found that optogenetically inhibiting the BLA itself immediately after training impaired cued-response retention in a Barnes maze task in males and females, confirming earlier pharmacological work in males alone. Subsequent experiments found that BLA-NAshell pathway inhibition impaired retention of cued-response and IA learning but had no effect on retention of spatial learning. However, the present work did not observe any effects of pathway stimulation immediately after cued-response or IA learning. Together, the present findings suggest the BLA modulates the consolidation of cued-response and IA, but not spatial, memory consolidation via NAshell projections.

Replication and extension of the subregion selectivity of glutamate-related changes within the nucleus accumbens associated with the incubation of cocaine-craving.

Cue-elicited drug-seeking behavior intensifies with the passage of time during withdrawal from drug taking and this "incubation of cocaine-craving" involves alterations in nucleus accumbens (NA) glutamate transmission. Here, we employed a combination of in vivo microdialysis and immunoblotting approaches to further examine changes in biochemical indices of glutamate transmission within NA subregions that accompany the incubation of cocaine-craving exhibited by male rats with a 10-day history of 6-h access to intravenous cocaine (0.25 mg/infusion). Immunoblotting on whole cell lysates from the core subregion (NAc core) revealed interactions between cocaine self-administration history, withdrawal and drug cue re-exposure for Homer2a/b, mGlu1, and GluN2b expression, as well as indices of Akt and ERK activity. With the exception of PKCε phosphorylation, most protein changes within the shell subregion (NAc shell) depended on drug cue re-exposure and cocaine history rather than varying in a consistent time-dependent manner. Reduced basal extracellular glutamate content was apparent only in the NAc core of cocaine-experienced rats during protracted (30 days) withdrawal and this was accompanied by a markedly blunted capacity of the mGlu1/5 agonist DHPG to elevate glutamate levels within this subregion. Finally, over-expressing neither Homer1c nor Homer2b within the NAc core during protracted cocaine withdrawal altered the magnitude of cue-elicited responding, its extinction or cocaine-primed reinstatement of drug-seeking behavior. The present findings are consistent with the extant literature implicating changes in Group 1 mGlu receptor function within the NAc core subregion as central to incubated cocaine-craving and provide further evidence against a major role for Homer proteins in gating incubated cocaine-craving. Further, our results provide novel correlational evidence implicating elevated Akt and blunted ERK activity within the NAc core as potential contributors to the expression of incubated cocaine-craving, worthy of future investigation.

Stimulation of kappa opioid receptors in the nucleus accumbens promotes feeding behavior in mice: Acute restoration of feeding during anorexia induced by 5-fluorouracil.

Though µ and δ opioid receptors are reported to regulate energy homeostasis, any role for κ opioid receptors in these processes remains unclear. The present study investigated the role of κ opioid receptors in regulation of feeding behavior and plasma glucose levels using nalfurafine, a κ opioid receptor agonist used clinically. Systemic injection of nalfurafine increased food intake under non-fasted conditions, but not after food deprivation, and this effect was inhibited by the κ opioid receptor antagonist norbinaltorphimine. In contrast, nalfurafine did not affect plasma glucose levels. I.c.v. injection of nalfurafine increased food intake, whereas systemic injection of nalfurafine methiodide, which does not penetrate the blood brain barrier, was without effect. In addition, nalfurafine tended to increase preproorexin mRNA in the hypothalamus. However, neither the orexin OX1 receptor antagonist YNT-1310 nor the non-selective orexin receptor antagonist suvorexant inhibited the increase in food intake induced by nalfurafine. While nalfurafine injected into the lateral hypothalamus did not affect food intake, nalfurafine injected into the nucleus accumbens increased food intake, which was inhibited by norbinaltorphimine. Finally, we examined the effect of nalfurafine on anorexia induced by the anti-cancer agent 5-fluorouracil. Reduced food intake at 2 days following 5-fluorouracil administration was alleviated across the first 3 h following daily injection of nalfurafine, though daily food intake was not influenced. These results indicate that nalfurafine promotes feeding behavior through stimulation of κ opioid receptors in the nucleus accumbens and may be a candidate for reducing anorexia due to anti-cancer agents.

Food Avoidance and Aversive Goal Value Computation in Anorexia Nervosa.

Anorexia nervosa (AN) is associated with food restriction and significantly low body weight, but the neurobiology of food avoidance in AN is unknown. Animal research suggests that food avoidance can be triggered by conditioned fear that engages the anterior cingulate and nucleus accumbens. We hypothesized that the neural activation during food avoidance in AN could be modeled based on aversive goal value processing. Nineteen females with AN and thirty healthy controls matched for age underwent functional magnetic resonance brain imaging while conducting a food avoidance task. During active control free-bid and computer-generated forced-bid trials, participants bid money to avoid eating food items. Brain activation was parametrically modulated with the trial-by-trial placed bids. During free-bid trials, the AN group engaged the caudate nucleus, nucleus accumbens, ventral anterior cingulate, and inferior and medial orbitofrontal cortex more than the control group. High- versus low-bid trials in the AN group were associated with higher caudate nucleus response. Emotion dysregulation and intolerance of uncertainty scores were inversely associated with nucleus accumbens free-bid trial brain response in AN. This study supports the idea that food avoidance behavior in AN involves aversive goal value computation in the nucleus accumbens, caudate nucleus, anterior cingulate, and orbitofrontal cortex.

Cryptogenic New-onset Refractory Status Epilepticus with Hyperintensity of T1-weighted Magnetic Resonance Imaging in the Bilateral Basal Ganglia: An Autopsy Report.

We present a 76-year-old man with cryptogenic new-onset refractory status epilepticus (C-NORSE) with an initial abnormal signal in the nucleus accumbens and a remarkable hyperintense signal on T1-weighted magnetic resonance imaging in the bilateral basal ganglia (BG). His status epilepticus did not respond to most anti-epileptic therapies or immunotherapies, and he died of sepsis. An autopsy revealed severe neuronal loss and hypertrophic astrocytes in the BG and limbic system, with no signs of inflammation or malignancy. This case suggests that lesions in the BG may reflect secondary degeneration and predict poor outcomes in C-NORSE.

Dopamine D2 receptors in the accumbal core region mediates the effects of fentanyl on sleep-wakefulness.

Fentanyl, a potent analgesic and addictive substance, significantly impacts sleep-wakefulness (S-W). Acutely, it promotes wake, whereas chronic abuse leads to severe sleep disruptions, including insomnia, which contributes to opioid use disorders (OUD), a chronic brain disease characterized by compulsive opioid use and harmful consequences. Although the critical association between sleep disruptions and fentanyl addiction is acknowledged, the precise mechanisms through which fentanyl influences sleep remain elusive. Recent studies highlight the role of the dopaminergic system of the nucleus accumbens (NAc) in S-W regulation, but its specific involvement in mediating fentanyl's effects on S-W remains unexplored. We hypothesized that dopamine D2 receptors mediate fentanyl-induced effects on S-W. To test this hypothesis, male C57BL/6J mice, instrumented with sleep recording electrodes and bilateral guide cannulas above the accumbal core region (NAcC), were utilized in this study. At dark onset, animals were bilaterally administered sulpiride (D2 receptors antagonist; 250 ng/side) in the NAcC followed by an intraperitoneal injection of fentanyl (1.2 mg/Kg). S-W was examined for the next 12 h. We found that systemic administration of fentanyl significantly increased wakefulness during the first 6 h of the dark which was followed by a significant increase in NREM and REM sleep during the second 6 h of the dark period. D2-receptor blockade significantly reduced this effect as evidenced by a significant reduction in fentanyl-induced wakefulness during first 6 h of dark period and sleep rebound during the second 6 h. Our findings suggest that D2 receptors in the NAcC plays a vital role in mediating the fentanyl-induced changes in S-W.

Chronic in vivo sequelae of repetitive acute mfb-DBS on accumbal dopamine and midbrain neuronal activity.

Medial Forebrain Bundle Deep Brain Stimulation (MFB-DBS) can have rapid and long lasting antidepressant effects in Treatment Resistant Depression (TRD) patients. The mechanisms are not well understood, but one hypothesis stipulates that modulation of the dopaminergic (DAergic) fibers contribute to the therapeutic outcome. Acute DBS effects on DA release have been studied; however, longitudinal studies with acute-repetitive DBS are lacking. Long-Evans accumbal DA release and Ventral Tegmental Area (VTA) calcium tonic and phasic signaling to different mfb-DBS parameters were measured using fiber photometry over 8 weeks, following acute and repetitive stimulation in behaving and non-behaving animals. DBS-induced release was observed in both targets, with increased frequency and DBS duration. 130 Hz stimulation increased phasic and tonic DA response over time, with the latter being a potential mechanism for its long-term clinical effectiveness. VTA calcium transients decreased, while phasic activity increased with frequency. Pulse width (PW)-mediated differential peak release timing also suggests potential parallel activation of diverse fiber types. Additionally, decreased DA transients rate during Elevated Plus Maze (EPM) suggests context and stimulation duration-dependent DA release. The data confirm chronic antidromic/orthodromic DAergic responses with stimulation parameter dependent variability, providing novel insights into temporal adaptations, connectivity and fiber recruitment on mfb DBS.

Delay discounting and nucleus accumbens functional connectivity are related to weight status in adolescents from the ABCD study.

BACKGROUND: Despite the growing epidemic of paediatric obesity, questions remain regarding potential neural mechanisms for individual risk. Delay discounting is a cognitive process of comparison of valuation between immediate and delayed reward, which has been inconsistently linked to weight status. Moreover, central to the brain's reward system is the nucleus accumbens, a region structurally and functionally altered in obesity. OBJECTIVES/METHODS: This study aimed to examine the relationships between two continuous metrics of weight status, performance on a monetary delay-discounting task and nucleus accumbens functional connectivity in 10-12-year-olds from the Adolescent Brain and Cognitive Development (ABCD) Study. RESULTS: Using multilevel longitudinal linear modelling, we found greater discounting was associated with higher BMI Z-scores (BMIz) and waist-to-height ratio Z-scores (WHtRz) (N = 3819). Moreover, we observed functional connectivity of the nucleus accumbens to the cingulo-opercular, dorsal attention, fronto-parietal, salience and ventral attention networks were predictive of BMIz (N = 1817). Nucleus accumbens functional connectivity was not found to mediate the association between delay-discounting behaviour and BMIz. CONCLUSIONS: Delay discounting and nucleus accumbens functional connectivity are independently related to weight status in a large sample of early adolescents. A better understanding of the relationship between reward and overeating behaviours may better inform obesity interventions.

Structural connectivity modifications following deep brain stimulation of the subcallosal cingulate and nucleus accumbens in severe anorexia nervosa.

PURPOSE: Anorexia nervosa (AN) is a mental health disorder characterized by significant weight loss and associated medical and psychological comorbidities. Conventional treatments for severe AN have shown limited effectiveness, leading to the exploration of novel interventional strategies, including deep brain stimulation (DBS). However, the neural mechanisms driving DBS interventions, particularly in psychiatric conditions, remain uncertain. This study aims to address this knowledge gap by examining changes in structural connectivity in patients with severe AN before and after DBS. METHODS: Sixteen participants, including eight patients with AN and eight controls, underwent baseline T1-weigthed and diffusion tensor imaging (DTI) acquisitions. Patients received DBS targeting either the subcallosal cingulate (DBS-SCC, N = 4) or the nucleus accumbens (DBS-NAcc, N = 4) based on psychiatric comorbidities and AN subtype. Post-DBS neuroimaging evaluation was conducted in four patients. Data analyses were performed to compare structural connectivity between patients and controls and to assess connectivity changes after DBS intervention. RESULTS: Baseline findings revealed that structural connectivity is significantly reduced in patients with AN compared to controls, mainly regarding callosal and subcallosal white matter (WM) tracts. Furthermore, pre- vs. post-DBS analyses in AN identified a specific increase after the intervention in two WM tracts: the anterior thalamic radiation and the superior longitudinal fasciculus-parietal bundle. CONCLUSIONS: This study supports that structural connectivity is highly compromised in severe AN. Moreover, this investigation preliminarily reveals that after DBS of the SCC and NAcc in severe AN, there are WM modifications. These microstructural plasticity adaptations may signify a mechanistic underpinning of DBS in this psychiatric disorder.

Incentive motivation for palatable food blocked by intra-accumbens melanin-concentrating hormone (MCH) receptor-1 antagonist in female rats.

Melanin-concentrating hormone (MCH) activity in the nucleus accumbens (Acb) has been shown to influence feeding behavior, yet this has not been characterized in terms of homeostatic vs. hedonic feeding processes. Hedonic feeding, driven by palatability rather than energy deficit, can be modeled through intra-Acb administration of the selective µ-opioid receptor agonist d-Ala2, NMe-Phe4, Glyol5-enkephalin (DAMGO), which preferentially increases consumption and incentive motivation to obtain preferred palatable food. Pharmacological activation of MCH 1 receptors (MCHR1) within Acb has been shown to promote general feeding of chow in males, but not females. However, the effects of MCH on the incentive motivation to obtain preferred palatable food have not been explored. Here, we investigated the role of MCHR1 within the Acb in DAMGO-induced incentive motivation to obtain a sucrose pellet reward. Female Sprague Dawley rats were trained and tested for operant responding under a progressive ratio (PR) breakpoint in response to concurrent intra-Acb administration of DAMGO (0 µg and 0.025 µg/.5 µl/side) immediately following intra-Acb administration of the MCHR1 antagonist (N-(3-{1-[4-(3,4-difluoro-phenoxy)-benzyl]-piperdin-4-yl}-4-methyl-phenyl)-isobutyramide (SNAP-94847; 0 µg, 1.5 µg, and 15 µg/.5 µl/side), in a counterbalanced fashion. As expected, DAMGO significantly increased PR breakpoint and overall active lever presses. SNAP-94847 did not influence PR breakpoint by itself, compared to vehicle; however, both 1.5 and 15 µg doses of SNAP-94847 significantly blocked the increased PR breakpoint produced by intra-Acb DAMGO. The results of the study demonstrate that Acb MCHR1 may play a specific role in the hedonically-driven motivation for palatable food in females.

Endogenous Regulator of G protein Signaling 14 (RGS14) suppresses cocaine-induced emotionally motivated behaviors in female mice.

Addictive drugs hijack the neuronal mechanisms of learning and memory in motivation and emotion processing circuits to reinforce their own use. Regulator of G-protein Signaling 14 (RGS14) is a natural suppressor of post-synaptic plasticity underlying learning and memory in the hippocampus. The present study used immunofluorescence and RGS14 knockout mice to assess the role of RGS14 in behavioral plasticity and reward learning induced by chronic cocaine in emotional-motivational circuits. We report that RGS14 is strongly expressed in discrete regions of the ventral striatum and extended amygdala in wild-type mice, and is co-expressed with D1 and D2 dopamine receptors in neurons of the nucleus accumbens (NAc). Of note, we found that RGS14 is upregulated in the NAc in mice with chronic cocaine history following acute cocaine treatment. We found significantly increased cocaine-induced locomotor sensitization, as well as enhanced conditioned place preference and conditioned locomotor activity in RGS14-deficient mice compared to wild-type littermates. Together, these findings suggest that endogenous RGS14 suppresses cocaine-induced plasticity in emotional-motivational circuits, implicating RGS14 as a protective agent against the maladaptive neuroplastic changes that occur during addiction.

Dietary protein restriction diminishes sucrose reward and reduces sucrose-evoked mesolimbic dopamine signaling in mice.

A growing literature suggests manipulating dietary protein status decreases sweet consumption in rodents and in humans. Underlying neurocircuit mechanisms have not yet been determined, but previous work points towards hedonic rather than homeostatic pathways. Here we hypothesized that a history of protein restriction reduces sucrose seeking by altering mesolimbic dopamine signaling in mice. We tested this hypothesis using established behavioral tests of palatability and conditioned reward, including the palatability contrast and conditioned place preference (CPP) tests. We used modern optical sensors for measuring real-time nucleus accumbens (NAc) dopamine dynamics during voluntary sucrose consumption, via fiber photometry, in male C57/Bl6J mice maintained on low-protein high-carbohydrate (LPHC) or control (CON) diet for ∼5 weeks. Our results showed that a history of protein restriction decreased the consumption of a sucrose 'dessert' in sated mice by ∼50% compared to controls [T-test, p < 0.05]. The dopamine release in NAc during sucrose consumption was reduced, also by ∼50%, in LPHC-fed mice compared to CON [T-test, p < 0.01]. Furthermore, LPHC-feeding blocked the sucrose-conditioned place preference we observed in CON-fed mice [paired T-test, p < 0.05], indicating reduced sucrose reward. This was accompanied by a 33% decrease in neuronal activation of the NAc core, as measured by c-Fos immunolabeling from brains collected directly after the CPP test [T-test, p < 0.05]. Together, these findings advance our mechanistic understanding of how dietary protein restriction decreases the consumption of sweets-by inhibiting the incentive salience of a sucrose reward, together with reduced sucrose-evoked dopamine release in NAc.

Radioneuromodulation of Nucleus Accumbens for Addiction: The First Animal Study.

OBJECTIVE: Addiction is a serious spiral where negative events or relationships trigger a craving even when the situation is caused by the addiction in the first place. Nucleus accumbens is identified as an important hub for the neural pathways involved in the addictive behavior. Stimulation of this structure was demonstrated to be beneficial for addiction previously, but radioneuromodulation was never investigated until today. This study aimed to investigate if radioneuromodulation of the nucleus accumbens has any effect on alcohol addiction. METHODS: An addiction model was used on 36 Long-Evans rats (18 females/18 males), via a 2-bottle intermittent access protocol, and the trial group received 100 Gy of gamma irradiation to their bilateral nucleus accumbens. Rats were followed up for an additional 15 weeks. Multiple sets of a behavioral test battery, a 4-week abstinence period, and quinine adulteration challenges were used to evaluate responses. RESULTS: The experiment showed that the intervention reduced alcohol preference in the presence of aversive stimuli in female rats, compared with the nonirradiated control rats, because the trial group showed a 9.83-point decrease in alcohol preference rate under high-dose quinine adulteration compared with baseline, whereas the control group did not show any decrease. There were also implications of additional benefits regarding weight control in females and behavioral tests in males. No evident adverse effect was observed with the treatment. CONCLUSIONS: This study indicates that nucleus accumbens radioneuromodulation, although not significantly affecting baseline consumption, reduces intake when an aversive stimulus is involved, implying improved self-control.

Shank3 deficiency alters midbrain GABAergic neuron morphology, GABAergic markers and synaptic activity in primary striatal neurons.

Abnormalities in gamma-aminobutyric acid (GABA)ergic neurotransmission play a role in the pathogenesis of autism, although the mechanisms responsible for alterations in specific brain regions remain unclear. Deficits in social motivation and interactions are core symptoms of autism, likely due to defects in dopaminergic neural pathways. Therefore, investigating the morphology and functional roles of GABAergic neurons within dopaminergic projection areas could elucidate the underlying etiology of autism. The aim of this study was to (1) compare the morphology and arborization of glutamate decarboxylase (GAD)-positive neurons from the midbrain tegmentum; (2) evaluate synaptic activity in primary neurons from the striatum; and (3) assess GABAergic postsynaptic puncta in the ventral striatum of wild-type (WT) and Shank3-deficient mice. We found a significant decrease in the number of short neurites in GAD positive primary neurons from the midbrain tegmentum in Shank3-deficient mice. The application of a specific blocker of GABAA receptors (GABAAR) revealed significantly increased frequency of spontaneous postsynaptic currents (sPSCs) in Shank3-deficient striatal neurons compared to their WT counterparts. The mean absolute amplitude of the events was significantly higher in striatal neurons from Shank3-deficient compared to WT mice. We also observed a significant reduction in gephyrin/GABAAR γ2 colocalization in the striatum of adult male Shank3-deficient mice. The gene expression of collybistin was significantly lower in the nucleus accumbens while gephyrin and GABAAR γ2 were lower in the ventral tegmental area (VTA) in male Shank3-deficient compared to WT mice. In conclusion, Shank3 deficiency leads to alterations in GABAergic neurons and impaired GABAergic function in dopaminergic brain areas. These changes may underlie autistic symptoms, and potential interventions modulating GABAergic activity in dopaminergic pathways may represent new treatment modality.

Abstinence from cocaine self-administration promotes microglia pruning of astrocytes which drives cocaine-seeking behavior.

Rodent drug self-administration leads to compromised ability of astrocytes to maintain glutamate homeostasis within the brain's reward circuitry, as well as reductions in surface area, volume, and synaptic colocalization of astrocyte membranes. However, the mechanisms driving astrocyte responses to cocaine are unknown. Here, we report that long-access cocaine self-administration followed by prolonged home cage abstinence results in decreased branching complexity of nucleus accumbens astrocytes, characterized by the loss of peripheral processes. Using a combination of confocal fluorescence microcopy and immuno-gold electron microscopy, we show that alterations in astrocyte structural features are driven by microglia phagocytosis, as labeled astrocyte membranes are found within microglia phagolysosomes. Inhibition of complement C3-mediated phagocytosis using the neutrophil inhibitory peptide (NIF) rescued astrocyte structure and decreased cocaine seeking behavior following cocaine self-administration and abstinence. Collectively, these results provide evidence for microglia pruning of accumbens astrocytes across cocaine abstinence which mediates cocaine craving.

Role of the Nucleus Accumbens in Signaled Avoidance Actions.

Animals, humans included, navigate their environments guided by sensory cues, responding adaptively to potential dangers and rewards. Avoidance behaviors serve as adaptive strategies in the face of signaled threats, but the neural mechanisms orchestrating these behaviors remain elusive. Current circuit models of avoidance behaviors indicate that the nucleus accumbens (NAc) in the ventral striatum plays a key role in signaled avoidance behaviors, but the nature of this engagement is unclear. Evolving perspectives propose the NAc as a pivotal hub for action selection, integrating cognitive and affective information to heighten the efficiency of both appetitive and aversive motivated behaviors. To unravel the engagement of the NAc during active and passive avoidance, we used calcium imaging fiber photometry to examine NAc GABAergic neuron activity in ad libitum moving mice performing avoidance behaviors. We then probed the functional significance of NAc neurons using optogenetics and genetically targeted or electrolytic lesions. We found that NAc neurons code contraversive orienting movements and avoidance actions. However, direct optogenetic inhibition or lesions of NAc neurons did not impair active or passive avoidance behaviors, challenging the notion of their purported pivotal role in adaptive avoidance. The findings emphasize that while the NAc encodes avoidance movements, it is not required for avoidance behaviors, highlighting the distinction between behavior encoding or representation and mediation or generation.