Candice Contet

Background: Histone deacetylase 6 (HDAC6) inhibition can alleviate depression‐ and anxiety‐like behaviors. Accordingly, HDAC6 may be a promising target to mitigate negative reinforcement in alcohol use disorder (AUD). We previously reported reduced α‐tubulin acetylation in mice withdrawn from chronic intermittent ethanol (CIE) vapor inhalation, suggesting potential HDAC6 hyperactivity in this mouse model of AUD. The present study aimed to probe the behavioral significance of this acetylation deficit by testing whether HDAC6 inhibition can reverse ethanol drinking escalation in CIE‐exposed mice. Methods: Male C57BL/6J mice were subjected to limited‐access ethanol drinking sessions (two‐bottle choice, 2BC) combined with CIE to escalate voluntary ethanol intake relative to air‐exposed counterparts (Air). Ethanol and saccharin intake during 2BC was measured after acute and subchronic administration of bavarostat, a brain‐penetrant HDAC6 inhibitor. Acetyl‐lysine and acetyl‐α‐tubulin levels were quantified via immunoblotting. Results: Acute administration of bavarostat at 100 mg/kg, but not lower doses, significantly reduced ethanol intake in both Air and CIE mice. Ethanol intake during subchronic administration of 100 mg/kg bavarostat was reduced on the first day in both Air and CIE mice compared to vehicle‐treated counterparts, but this effect was lost on subsequent days. CIE mice also consumed more saccharin than Air controls. Bavarostat did not impact saccharin intake in either group. When saccharin was offered along with ethanol, CIE mice consumed significantly more ethanol and less saccharin than Air counterparts, indicating intact taste discrimination. Bavarostat administered prior to brain collection significantly increased acetyl‐lysine and acetyl‐α‐tubulin levels in the frontal cortex, confirming reduced HDAC6 activity. These levels did not differ between Air and CIE mice. Conclusions: Systemic administration of bavarostat reduces voluntary ethanol drinking in mice. This effect is dose‐dependent, selective for ethanol, independent of ethanol dependence, and transient. These findings support HDAC6 as a viable target to acutely reduce the drive to consume ethanol.

The neurocircuitry changes mediating the development and maintenance of an alcohol use disorder are complex and dynamic. The parasubthalamic nucleus (PSTN), a small nucleus of the posterior lateral hypothalamus best known for suppressing appetite, is interconnected with brain regions disrupted in addiction; yet its potential role in the regulation of alcohol consumption had never been examined. Here we show that the PSTN exerts potent control over alcohol drinking in mice. Remarkably, the influence of endogenous PSTN activity on voluntary alcohol consumption switches from inhibitory to stimulatory upon induction of alcohol dependence. Among PSTN cells, Crh neurons represent a unique subpopulation that promotes alcohol drinking and fires more in dependent mice. Alcohol intake escalation driven by PSTN Crh neurons involves thalamic output and behavioral disinhibition. Based on our results, PSTN Crh neurons could represent a critical node in the brain circuitry overactive in alcohol addiction driven by reward seeking in humans.

Background: Memory impairment is frequent among alcohol use disorder (AUD) patients, and we lack specific biomarkers to detect it. Certain apolipoproteins were linked to cognition, and carrying the APOE4 gene is a vulnerability factor to memory impairment in AUD patients. We explored memory deficits in alcohol‐dependent male mice and humans versus controls, and their relationship to Apolipoprotein AI (APOAI), apolipoprotein B (APOB), and apolipoprotein E (APOE) plasma levels.Methods: Male C57BL/6J mice underwent voluntary alcohol drinking (two‐bottle choice, 2BC) and chronic intermittent ethanol vapor exposure (CIE) as a model of alcohol dependence; memory was assessed by the Object Location Test (OLT) and Novel Object Recognition Test (NORT). Additionally, male AUD‐diagnosed patients were recruited in Spain during an alcohol dishabituation program and assessed by the Wechsler Memory Scale‐IV (WMS‐IV). Plasma APOAI, APOB, and APOE levels were checked in mice and humans by ELISA kits and Luminex immunoassay technology. APOAI immunolabeling was quantified in mouse brain in early withdrawal and following alcohol consumption.Results: CIE‐2BC mice (n = 8) escalated alcohol consumption compared to Air‐2BC controls (n = 11) and showed deficits in spatial memory (OLT) and recognition memory (NORT) while AUD patients (n = 12) showed deficits in verbal and visual memory (WMS‐IV) versus controls (n = 16). Higher plasma levels of APOAI were detected in CIE‐2BC mice and AUD patients, with no differences in APOB and APOE in animals and humans. Significant negative correlations were found between levels of APOAI, APOB, and APOE and memory function tests/scales in the entire sample, with APOAI showing consistent results in both animals and humans. APOAI immunoreactivity was detected in the mice subfornical organ, but the signal did not differ between experimental groups.Conclusions: Both CIE‐2BC mice and AUD patients exhibited elevated plasma levels of APOAI during early abstinence. APOAI correlated with poorer memory performance in both species, suggesting a potential role for this apolipoprotein in the context of alcohol‐induced cognitive impairment.

Corticotropin-releasing factor (CRF, encoded by Crh ) signaling is thought to play a critical role in the development of excessive alcohol drinking and the emotional and physical pain associated with alcohol withdrawal. Here, we investigated the parasubthalamic nucleus (PSTN) as a potential source of CRF relevant to the control of alcohol consumption, affect, and nociception in mice. We identified PSTN Crh neurons as a neuronal subpopulation that exerts a potent and unique influence on behavior by promoting not only alcohol but also saccharin drinking, while PSTN neurons are otherwise known to suppress consummatory behaviors. Furthermore, PSTN Crh neurons are causally implicated in the escalation of alcohol and saccharin intake produced by chronic intermittent ethanol (CIE) vapor inhalation, a mouse model of alcohol use disorder. In contrast to our predictions, the ability of PSTN Crh neurons to increase alcohol drinking is not mediated by CRF ₁ signaling. Moreover, the pattern of behavioral disinhibition and reduced nociception driven by their activation does not support a role of negative reinforcement as a motivational basis for the concomitant increase in alcohol drinking. Finally, silencing Crh expression in the PSTN slowed down the escalation of alcohol intake in mice exposed to CIE and accelerated their recovery from withdrawal-induced mechanical hyperalgesia. Altogether, our results suggest that PSTN Crh neurons may represent an important node in the brain circuitry linking alcohol use disorder with sweet liking and novelty seeking.

The parasubthalamic nucleus (PSTN) is activated by refeeding after food deprivation and several PSTN subpopulations have been shown to suppress feeding. However, no study to date directly addressed the role of PSTN neurons activated upon food access in the control of ensuing food consumption. Here we identify consumption latency as a sensitive behavioral indicator of PSTN activity, and show that, in hungry mice, the ensemble of refeeding-activated PSTN neurons drastically increases the latency to initiate refeeding with both familiar and a novel, familiar food, but does not control the amount of food consumed. In thirsty mice, this ensemble also delays sucrose consumption but accelerates water consumption, possibly reflecting anticipatory prandial thirst, with again no influence on the amount of fluid consumed. We next sought to identify which subpopulations of PSTN neurons might be driving these latency effects, using cell-type and pathway-specific chemogenetic manipulations. Our results suggest a prominent role of PSTN Tac1 neurons projecting to the central amygdala in the hindrance of feeding initiation. While PSTN Crh neurons also delay the latency of hungry mice to ingest familiar foods, they surprisingly promote the consumption of novel, palatable substances. Furthermore, PSTN Crh neurons projecting to the bed nucleus of the stria terminalis accelerate rehydration in thirsty mice. Our results demonstrate the key role of endogenous PSTN activity in the control of feeding and drinking initiation and delineate specific circuits mediating these effects, which may have relevance for eating disorders.

Large conductance potassium (BK) channels are among the most sensitive molecular targets of ethanol and genetic variations in the channel-forming α subunit have been nominally associated with alcohol use disorders. However, whether the action of ethanol at BK α influences the motivation to drink alcohol remains to be determined. To address this question, we first tested the effect of systemically administered BK channel modulators on voluntary alcohol consumption in C57BL/6J males. Penitrem A (blocker) exerted dose-dependent effects on moderate alcohol intake, while paxilline (blocker) and BMS-204352 (opener) were ineffective. Because pharmacological manipulations are inherently limited by non-specific effects, we then sought to investigate the behavioral relevance of ethanol’s direct interaction with BK α by introducing in the mouse genome a point mutation known to render BK channels insensitive to ethanol while preserving their physiological function. The BK α K361N substitution prevented ethanol from reducing spike threshold in medial habenula neurons. However, it did not alter acute responses to ethanol in vivo, including ataxia, sedation, hypothermia, analgesia, and conditioned place preference. Furthermore, the mutation did not have reproducible effects on alcohol consumption in limited, continuous, or intermittent access home cage two-bottle choice paradigms conducted in both males and females. Notably, in contrast to previous observations made in mice missing BK channel auxiliary β subunits, the BK α K361N substitution had no significant impact on ethanol intake escalation induced by chronic intermittent alcohol vapor inhalation. It also did not affect the metabolic and locomotor consequences of chronic alcohol exposure. Altogether, these data suggest that the direct interaction of ethanol with BK α does not mediate the alcohol-related phenotypes examined here in mice.

The parasubthalamic nucleus (PSTN) is responsive to refeeding after food deprivation and PSTN subpopulations can suppress feeding. However, no study directly addressed the role of PSTN neurons activated upon food access resumption. Here we show that the ensemble of refeeding-activated PSTN neurons drastically increases the latency to initiate refeeding with both familiar and novel food but exerts limited control over the amount of food consumed by hungry mice. This ensemble also delays sucrose consumption but accelerates water consumption in thirsty mice. We next sought to identify which subpopulations of PSTN neurons might be driving these effects. We discovered that PSTN Tac1 neurons projecting to the CeA selectively suppress feeding initiation while PSTN Crh neurons surprisingly promote the consumption of novel, palatable substances. Our results demonstrate the key role of endogenous PSTN activity in the control of feeding initiation and identify PSTN subpopulations counteracting each other’s influence on consummatory behaviors.

Alcohol use disorders can be driven by negative reinforcement. Alterations of the microtubule cytoskeleton have been associated with mood regulation in the context of depression. Notably, MAP4343, a pregnenolone derivative known to promote tubulin assembly, has antidepressant properties. In the present study, we tested the hypothesis that MAP4343 may reduce excessive alcohol drinking in a mouse model of alcohol dependence by normalizing affect during withdrawal. Adult male C57BL/6J mice were given limited access to voluntary alcohol drinking and ethanol intake escalation was induced by chronic intermittent ethanol (CIE) vapor inhalation. Chronic, but not acute, administration of MAP4343 reduced ethanol intake and this effect was more pronounced in CIE-exposed mice. There was a complex interaction between the effects of MAP4343 and alcohol on affective behaviors. In the elevated plus maze, chronic MAP4343 tended to increase open-arm exploration in alcohol-naive mice but reduced it in alcohol-withdrawn mice. In the tail suspension test, chronic MAP4343 reduced immobility selectively in Air-exposed alcohol-drinking mice. Finally, chronic MAP4343 countered the plasma corticosterone reduction induced by CIE. Parallel analysis of tubulin post-translational modifications revealed lower α-tubulin acetylation in the medial prefrontal cortex of CIE-withdrawn mice. Altogether, these data support the relevance of microtubules as a therapeutic target for the treatment of AUD.

Background: Stressful early‐life experiences increase the risk of developing an alcohol use disorder. We previously found that male C57BL/6J mice reared under limited bedding and nesting (LBN) conditions, a model of early‐life adversity, escalate their ethanol intake in limited‐access two‐bottle choice (2BC) sessions faster than control (CTL)‐reared counterparts when exposed to chronic intermittent ethanol (CIE) vapor inhalation. However, the alcohol consumption of female littermates was not affected by LBN or CIE. In the present study, we sought to determine whether this phenotype reflected a general insensitivity of female mice to the influence of early‐life stress on alcohol responses.Methods: In a first experiment, CTL and LBN females with a history of 2BC combined or not with CIE were tested in affective and nociceptive assays during withdrawal. In a second group of CTL and LBN females, we examined ethanol‐induced antinociception, sedation, plasma clearance, and c‐Fos induction.Results: In females withdrawn from chronic 2BC, CIE increased digging, reduced grooming, and increased immobility in the tail suspension test regardless of early‐life history. In contrast, LBN rearing lowered mechanical nociceptive thresholds regardless of CIE exposure. In females acutely treated with ethanol, LBN rearing facilitated antinociception and delayed the onset of sedation without influencing ethanol clearance rate or c‐Fos induction in the paraventricular nucleus of the hypothalamus, paraventricular nucleus of the thalamus, central nucleus of the amygdala, or auditory cortex.Conclusion: CIE withdrawal produced multiple indices of negative affect in C57BL/6J females, suggesting that their motivation to consume alcohol may differ from air‐exposed counterparts despite equivalent intake. Contrasted with our previous findings in males, LBN‐induced mechanical hyperalgesia in chronic alcohol drinkers was specific to females. Lower nociceptive thresholds combined with increased sensitivity to the acute antinociceptive effect of ethanol may contribute to reinforcing ethanol consumption in LBN females but are not sufficient to increase their intake.

Prefrontal circuits are thought to underlie aberrant emotion contributing to relapse in abstinence; however, the discrete cell-types and mechanisms remain largely unknown. Corticotropin-releasing factor and its cognate type-1 receptor, a prominent brain stress system, is implicated in anxiety and alcohol use disorder (AUD). Here, we tested the hypothesis that medial prefrontal cortex CRF1-expressing (mPFC^CRF1+) neurons comprise a distinct population that exhibits neuroadaptations following withdrawal from chronic ethanol underlying AUD-related behavior. We found that mPFC^CRF1+ neurons comprise a glutamatergic population with distinct electrophysiological properties and regulate anxiety and conditioned rewarding effects of ethanol. Notably, mPFC^CRF1+ neurons undergo unique neuroadaptations compared to neighboring neurons including a remarkable decrease in excitability and glutamatergic signaling selectively in withdrawal, which is driven in part by the basolateral amygdala. To gain mechanistic insight into these electrophysiological adaptations, we sequenced the transcriptome of mPFC^CRF1+ neurons and found that withdrawal leads to an increase in colony-stimulating factor 1 (CSF1) in this population. We found that selective overexpression of CSF1 in mPFC^CRF1+ neurons is sufficient to decrease glutamate transmission, heighten anxiety, and abolish ethanol reinforcement, providing mechanistic insight into the observed mPFC^CRF1+ synaptic adaptations in withdrawal that drive these behavioral phenotypes. Together, these findings highlight mPFC^CRF1+ neurons as a critical site of enduring adaptations that may contribute to the persistent vulnerability to ethanol misuse in abstinence, and CSF1 as a novel target for therapeutic intervention for withdrawal-related negative affect.