• Energy Research

BackgroundAlcohol use disorders are characterized by a complex behavioral symptomatology, which includes the loss of control over alcohol consumption and the emergence of a negative affective state when alcohol is not consumed. Some of these symptoms can be recapitulated in rodent models, for instance following chronic intermittent ethanol (EtOH; CIE) vapor inhalation. However, the detection of negative affect in mice withdrawn from CIE has proven challenging and variable between strains. This study aimed to detect reliable indices of negative emotionality in CIE‐exposed C57BL/6J (C57) and DBA/2J (DBA) mice. Males were used because they are known to escalate their voluntary EtOH consumption upon CIE exposure, which is hypothesized to be driven by negative reinforcement (relief from negative affect).MethodsAdult male mice were exposed to 4 to 6 weeks of CIE and were evaluated 3 to 10 days into withdrawal in the social approach, novelty‐suppressed feeding, digging, marble burying, and bottle brush tests.ResultsWithdrawal from CIE decreased sociability in DBA mice but not in C57 mice. Conversely, hyponeophagia was exacerbated by CIE in C57 mice but not in DBA mice. Withdrawal from CIE robustly increased digging activity in both strains, even in the absence of marbles. Aggressive responses to bottle brush attacks were elevated in both C57 and DBA mice following CIE exposure, but CIE had an opposite effect on defensive responses in the 2 strains (increase in C57 vs. decrease in DBA).ConclusionsOur results indicate that withdrawal from CIE elicits negative emotionality in both C57 and DBA mice, but different tests need to be used to measure the anxiogenic‐like effects of withdrawal in each strain. Increased digging activity and irritability‐like behavior represent novel indices of affective dysfunction associated with withdrawal from CIE in both mouse strains. Our findings enrich the characterization of the affective symptomatology of protracted withdrawal from CIE in mice.

BackgroundAlcohol use disorders are characterized by a complex behavioral symptomatology, which includes the loss of control over alcohol consumption and the emergence of a negative affective state when alcohol is not consumed. Some of these symptoms can be recapitulated in rodent models, for instance following chronic intermittent ethanol (EtOH; CIE) vapor inhalation. However, the detection of negative affect in mice withdrawn from CIE has proven challenging and variable between strains. This study aimed to detect reliable indices of negative emotionality in CIE‐exposed C57BL/6J (C57) and DBA/2J (DBA) mice. Males were used because they are known to escalate their voluntary EtOH consumption upon CIE exposure, which is hypothesized to be driven by negative reinforcement (relief from negative affect).MethodsAdult male mice were exposed to 4 to 6 weeks of CIE and were evaluated 3 to 10 days into withdrawal in the social approach, novelty‐suppressed feeding, digging, marble burying, and bottle brush tests.ResultsWithdrawal from CIE decreased sociability in DBA mice but not in C57 mice. Conversely, hyponeophagia was exacerbated by CIE in C57 mice but not in DBA mice. Withdrawal from CIE robustly increased digging activity in both strains, even in the absence of marbles. Aggressive responses to bottle brush attacks were elevated in both C57 and DBA mice following CIE exposure, but CIE had an opposite effect on defensive responses in the 2 strains (increase in C57 vs. decrease in DBA).ConclusionsOur results indicate that withdrawal from CIE elicits negative emotionality in both C57 and DBA mice, but different tests need to be used to measure the anxiogenic‐like effects of withdrawal in each strain. Increased digging activity and irritability‐like behavior represent novel indices of affective dysfunction associated with withdrawal from CIE in both mouse strains. Our findings enrich the characterization of the affective symptomatology of protracted withdrawal from CIE in mice.

BackgroundLarge conductance, calcium‐ and voltage‐activated potassium (BK) channels regulate neuronal excitability and neurotransmission. They can be directly activated by ethanol (EtOH) and they may be implicated in EtOH dependence. In this study, we sought to determine the influence of the auxiliaryβ1 andβ4 subunits on EtOH metabolism, acute sensitivity to EtOH intoxication, acute functional tolerance, chronic tolerance, and handling‐induced convulsions during withdrawal.MethodsMotor coordination, righting reflex, and body temperature were evaluated inBKβ1 andβ4 knockout, heterozygous, and wild‐type mice following acute EtOH administration. Chronic tolerance and physical dependence were induced by chronic intermittent inhalation of EtOH vapor.ResultsConstitutive deficiency inBKβ1 orβ4 subunits did not alter the clearance rate of EtOH, acute sensitivity to EtOH‐induced ataxia, sedation, and hypothermia, nor acute functional tolerance to ataxia.BKβ1 deletion reduced chronic tolerance to sedation and abolished chronic tolerance to hypothermia, whileBKβ4 deletion did not affect these adaptations to chronic EtOH exposure. Finally, the absence ofBKβ1 accelerated the appearance, while the absence ofBKβ4 delayed the resolution, of the hyperexcitable state associated with EtOH withdrawal.ConclusionsAltogether, the present findings reveal the critical role ofBKβ1 in behavioral adaptations to prolonged, repeated EtOH intoxication.

BackgroundLarge conductance, calcium‐ and voltage‐activated potassium (BK) channels regulate neuronal excitability and neurotransmission. They can be directly activated by ethanol (EtOH) and they may be implicated in EtOH dependence. In this study, we sought to determine the influence of the auxiliaryβ1 andβ4 subunits on EtOH metabolism, acute sensitivity to EtOH intoxication, acute functional tolerance, chronic tolerance, and handling‐induced convulsions during withdrawal.MethodsMotor coordination, righting reflex, and body temperature were evaluated inBKβ1 andβ4 knockout, heterozygous, and wild‐type mice following acute EtOH administration. Chronic tolerance and physical dependence were induced by chronic intermittent inhalation of EtOH vapor.ResultsConstitutive deficiency inBKβ1 orβ4 subunits did not alter the clearance rate of EtOH, acute sensitivity to EtOH‐induced ataxia, sedation, and hypothermia, nor acute functional tolerance to ataxia.BKβ1 deletion reduced chronic tolerance to sedation and abolished chronic tolerance to hypothermia, whileBKβ4 deletion did not affect these adaptations to chronic EtOH exposure. Finally, the absence ofBKβ1 accelerated the appearance, while the absence ofBKβ4 delayed the resolution, of the hyperexcitable state associated with EtOH withdrawal.ConclusionsAltogether, the present findings reveal the critical role ofBKβ1 in behavioral adaptations to prolonged, repeated EtOH intoxication.

AbstractAlcohol 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.

AbstractAlcohol 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.

The corticotropin releasing factor (CRF) system in the central amygdala (CeA) has been implicated in the effects of acute ethanol and the development of alcohol dependence. We previously demonstrated that CRF receptor 1 (CRF1) neurons comprise a specific component of the CeA microcircuitry that is selectively engaged by acute ethanol. To investigate the impact of chronic ethanol exposure on inhibitory signaling in CRF1+ CeA neurons, we used CRF1:GFP mice subjected to chronic intermittent ethanol (CIE) inhalation and examined changes in local inhibitory control, the effects of acute ethanol, and the output of these neurons from the CeA. Following CIE, CRF1+ neurons displayed decreased phasic inhibition and a complete loss of tonic inhibition that persisted into withdrawal. CRF1− neurons showed a cell type-specific upregulation of both phasic and tonic signaling with CIE, the latter of which persists into withdrawal and is likely mediated by δ subunit-containing GABAAreceptors. The loss of tonic inhibition with CIE was seen in CRF1+ and CRF1− neurons that project out of the CeA and into the bed nucleus of the stria terminalis. CRF1+ projection neurons displayed an increased baseline firing rate and loss of sensitivity to acute ethanol following CIE. These data demonstrate that chronic ethanol exposure produces profound and long-lasting changes in local inhibitory control of the CeA, resulting in an increase in the output of the CeA and the CRF1 receptor system, in particular. These cellular changes could underlie the behavioral manifestations of alcohol dependence and potentially contribute to the pathology of addiction.SIGNIFICANCE STATEMENTThe corticotropin releasing factor (CRF) system in the central amygdala (CeA) has been implicated in the effects of acute and chronic ethanol. We showed previously that CRF receptor 1-expressing (CRF1+) neurons in the CeA are under tonic inhibitory control and are differentially regulated by acute ethanol (Herman et al., 2013). Here we show that the inhibitory control of CRF1+ CeA neurons is lost with chronic ethanol exposure, likely by a functional switch in local tonic signaling. The loss of tonic inhibition is seen in CRF1+ projection neurons, suggesting that a critical consequence of chronic ethanol exposure is an increase in the output of the CeA CRF1 system, a neuroadaptation that may contribute to the behavioral consequences of alcohol dependence.

The corticotropin releasing factor (CRF) system in the central amygdala (CeA) has been implicated in the effects of acute ethanol and the development of alcohol dependence. We previously demonstrated that CRF receptor 1 (CRF1) neurons comprise a specific component of the CeA microcircuitry that is selectively engaged by acute ethanol. To investigate the impact of chronic ethanol exposure on inhibitory signaling in CRF1+ CeA neurons, we used CRF1:GFP mice subjected to chronic intermittent ethanol (CIE) inhalation and examined changes in local inhibitory control, the effects of acute ethanol, and the output of these neurons from the CeA. Following CIE, CRF1+ neurons displayed decreased phasic inhibition and a complete loss of tonic inhibition that persisted into withdrawal. CRF1− neurons showed a cell type-specific upregulation of both phasic and tonic signaling with CIE, the latter of which persists into withdrawal and is likely mediated by δ subunit-containing GABAAreceptors. The loss of tonic inhibition with CIE was seen in CRF1+ and CRF1− neurons that project out of the CeA and into the bed nucleus of the stria terminalis. CRF1+ projection neurons displayed an increased baseline firing rate and loss of sensitivity to acute ethanol following CIE. These data demonstrate that chronic ethanol exposure produces profound and long-lasting changes in local inhibitory control of the CeA, resulting in an increase in the output of the CeA and the CRF1 receptor system, in particular. These cellular changes could underlie the behavioral manifestations of alcohol dependence and potentially contribute to the pathology of addiction.SIGNIFICANCE STATEMENTThe corticotropin releasing factor (CRF) system in the central amygdala (CeA) has been implicated in the effects of acute and chronic ethanol. We showed previously that CRF receptor 1-expressing (CRF1+) neurons in the CeA are under tonic inhibitory control and are differentially regulated by acute ethanol (Herman et al., 2013). Here we show that the inhibitory control of CRF1+ CeA neurons is lost with chronic ethanol exposure, likely by a functional switch in local tonic signaling. The loss of tonic inhibition is seen in CRF1+ projection neurons, suggesting that a critical consequence of chronic ethanol exposure is an increase in the output of the CeA CRF1 system, a neuroadaptation that may contribute to the behavioral consequences of alcohol dependence.