RESUMO
Currently available pharmacotherapies for treating alcohol use disorder (AUD) suffer from deleterious side effects and are not efficacious in diverse populations. Clinical and preclinical studies provide evidence that the Kcnq family of genes that encode KV7 channels influence alcohol intake and dependence. KV7 channels are a class of slowly activating voltage-dependent K+ channels that regulate neuronal excitability. Studies indicate that the KV7 channel positive modulator retigabine can decrease dopaminergic neuron firing, alter dopamine (DA) release, and reduce alcohol intake in heavy drinking rodents. Given the critical nature of ventral tegmental area (VTA) DA to the addiction process and predominant expression of Kcnq4 in DA neurons, we investigated the role of midbrain Kcnq genes and KV7 channels in the VTA of genetically diverse mice and long-term heavy drinking rats, respectively. Integrative bioinformatics analysis identified negative correlations between midbrain Kcnq4 expression and alcohol intake and seeking behaviors. Kcnq4 expression levels were also correlated with dopaminergic-related phenotypes in BXD strains, and Kcnq4 was present in support intervals for alcohol sensitivity and alcohol withdrawal severity QTLs in rodents. Pharmacological validation studies revealed that VTA KV7 channels regulate excessive alcohol intake in rats with a high-drinking phenotype. Administration of a novel and selective KV7.2/4 channel positive modulator also reduced alcohol drinking in rats. Together, these findings indicate that midbrain Kcnq4 expression regulates alcohol-related behaviors in genetically diverse mice and provide evidence that KV7.4 channels are a critical mediator of excessive alcohol drinking.
Assuntos
Transtornos Relacionados ao Uso de Álcool/metabolismo , Canais de Potássio KCNQ/metabolismo , Área Tegmentar Ventral/metabolismo , Dissuasores de Álcool/farmacologia , Consumo de Bebidas Alcoólicas/tratamento farmacológico , Consumo de Bebidas Alcoólicas/metabolismo , Transtornos Relacionados ao Uso de Álcool/tratamento farmacológico , Animais , Dopamina/metabolismo , Comportamento de Procura de Droga/efeitos dos fármacos , Comportamento de Procura de Droga/fisiologia , Feminino , Predisposição Genética para Doença , Masculino , Camundongos , Atividade Motora/efeitos dos fármacos , Atividade Motora/fisiologia , Ratos Wistar , Área Tegmentar Ventral/efeitos dos fármacosRESUMO
Alcohol use disorder is a chronic relapsing brain disease characterized by the loss of ability to control alcohol (ethanol) intake despite knowledge of detrimental health or personal consequences. Clinical and pre-clinical models provide strong evidence for chronic ethanol-associated alterations in glutamatergic signaling and impaired synaptic plasticity in the nucleus accumbens (NAc). However, the neural mechanisms that contribute to aberrant glutamatergic signaling in ethanol-dependent individuals in this critical brain structure remain unknown. Using an unbiased proteomic approach, we investigated the effects of chronic intermittent ethanol (CIE) exposure on neuroadaptations in postsynaptic density (PSD)-enriched proteins in the NAc of ethanol-dependent mice. Compared with controls, CIE exposure significantly changed expression levels of 50 proteins in the PSD-enriched fraction. Systems biology and functional annotation analyses demonstrated that the dysregulated proteins are expressed at tetrapartite synapses and critically regulate cellular morphology. To confirm this latter finding, the density and morphology of dendritic spines were examined in the NAc core of ethanol-dependent mice. We found that CIE exposure and withdrawal differentially altered dendrite diameter and dendritic spine density and morphology. Through the use of quantitative proteomics and functional annotation, these series of experiments demonstrate that ethanol dependence produces neuroadaptations in proteins that modify dendritic spine morphology. In addition, these studies identified novel PSD-related proteins that contribute to the neurobiological mechanisms of ethanol dependence that drive maladaptive structural plasticity of NAc neurons.
Assuntos
Alcoolismo/metabolismo , Depressores do Sistema Nervoso Central/farmacologia , Espinhas Dendríticas/efeitos dos fármacos , Etanol/farmacologia , Núcleo Accumbens/efeitos dos fármacos , Densidade Pós-Sináptica/efeitos dos fármacos , Proteoma/efeitos dos fármacos , Animais , Western Blotting , Depressores do Sistema Nervoso Central/administração & dosagem , Cromatografia Líquida , Espinhas Dendríticas/metabolismo , Modelos Animais de Doenças , Etanol/administração & dosagem , Masculino , Camundongos , Núcleo Accumbens/metabolismo , Densidade Pós-Sináptica/metabolismo , Proteoma/metabolismo , Síndrome de Abstinência a Substâncias/etiologia , Síndrome de Abstinência a Substâncias/metabolismo , Espectrometria de Massas em TandemRESUMO
Alcohol use disorders (AUDs) are a major public health issue and produce enormous societal and economic burdens. Current Food and Drug Administration (FDA)-approved pharmacotherapies for treating AUDs suffer from deleterious side effects and are only effective in a subset of individuals. It is therefore essential to find improved medications for the management of AUDs. Emerging evidence suggests that anticonvulsants are a promising class of drugs for treating individuals with AUDs. In these studies, we used integrative functional genomics to demonstrate that genes that encode Kv7 channels (i.e. Kcnq2/3) are related to alcohol (ethanol) consumption, preference and acceptance in rodents. We then tested the ability of the FDA-approved anticonvulsant retigabine, a Kv7 channel opener, to reduce voluntary ethanol consumption of Wistar rats in a two-bottle choice intermittent alcohol access paradigm. Systemic administration and microinjections of retigabine into the nucleus accumbens significantly reduced alcohol drinking, and retigabine was more effective at reducing intake in high- versus low-drinking populations of Wistar rats. Prolonged voluntary drinking increased the sensitivity to the proconvulsant effects of pharmacological blockade of Kv7 channels and altered surface trafficking and SUMOylation patterns of Kv7.2 channels in the nucleus accumbens. These data implicate Kcnq2/3 in the regulation of ethanol drinking and demonstrate that long-term drinking produces neuroadaptations in Kv7 channels. In addition, these results have identified retigabine as a potential pharmacotherapy for treating AUDs and Kv7 channels as a novel therapeutic target for reducing heavy drinking.
Assuntos
Consumo de Bebidas Alcoólicas/fisiopatologia , Canal de Potássio KCNQ2/efeitos dos fármacos , Canal de Potássio KCNQ3/efeitos dos fármacos , Núcleo Accumbens/efeitos dos fármacos , Dissuasores de Álcool/farmacologia , Convulsões por Abstinência de Álcool/induzido quimicamente , Animais , Antracenos/farmacologia , Anticonvulsivantes/farmacologia , Comportamento Animal/efeitos dos fármacos , Carbamatos/farmacologia , Condicionamento Operante/efeitos dos fármacos , Genômica , Canal de Potássio KCNQ2/genética , Canal de Potássio KCNQ3/genética , Masculino , Moduladores de Transporte de Membrana/farmacologia , Microinjeções , Atividade Motora/efeitos dos fármacos , Fenilenodiaminas/farmacologia , Bloqueadores dos Canais de Potássio/farmacologia , Ratos Wistar , Sumoilação/efeitos dos fármacos , Percepção Gustatória/efeitos dos fármacosRESUMO
Repeated exposure to ethanol followed by withdrawal leads to alterations in glutamatergic signaling and impaired synaptic plasticity in the nucleus accumbens (NAc) in both clinical and preclinical models of ethanol exposure. Homer2 is a member of a family of postsynaptic density (PSD) scaffolding proteins that functions in part to cluster N-methyl-D-aspartate (NMDA) signaling complexes in the PSD, and has been shown to be critically important for plasticity in multiple models of drug and alcohol abuse. Here we used Homer2 knockout (KO) mice and a chronic intermittent intraperitoneal (IP) ethanol injection model to investigate a potential role for the protein in ethanol-induced adaptations in dendritic spine morphology and PSD protein expression. While deletion of Homer2 was associated with increased density of long spines on medium spiny neurons of the NAc core of saline treated mice, ethanol exposure had no effect on dendritic spine morphology in either wild-type (WT) or Homer2 KO mice. Western blot analysis of tissue samples from the NAc enriched for PSD proteins revealed a main effect of ethanol treatment on the expression of GluN2B, but there was no effect of genotype or treatment on the expression other glutamate receptor subunits or PSD95. These data indicate that the global deletion of Homer2 leads to aberrant regulation of dendritic spine morphology in the NAc core that is associated with an increased density of long, thin spines. Unexpectedly, intermittent IP ethanol did not affect spine morphology in either WT or KO mice. Together these data implicate Homer2 in the formation of long, thin spines and further supports its role in neuronal structure.
RESUMO
Small-conductance Ca(2+)-activated K(+) (KCa2) channels control neuronal excitability and synaptic plasticity, and have been implicated in substance abuse. However, it is unknown if genes that encode KCa2 channels (KCNN1-3) influence alcohol and drug addiction. In the present study, an integrative functional genomics approach shows that genetic datasets for alcohol, nicotine, and illicit drugs contain the family of KCNN genes. Alcohol preference and dependence QTLs contain KCNN2 and KCNN3, and Kcnn3 transcript levels in the nucleus accumbens (NAc) of genetically diverse BXD strains of mice predicted voluntary alcohol consumption. Transcript levels of Kcnn3 in the NAc negatively correlated with alcohol intake levels in BXD strains, and alcohol dependence enhanced the strength of this association. Microinjections of the KCa2 channel inhibitor apamin into the NAc increased alcohol intake in control C57BL/6J mice, while spontaneous seizures developed in alcohol-dependent mice following apamin injection. Consistent with this finding, alcohol dependence enhanced the intrinsic excitability of medium spiny neurons in the NAc core and reduced the function and protein expression of KCa2 channels in the NAc. Altogether, these data implicate the family of KCNN genes in alcohol, nicotine, and drug addiction, and identify KCNN3 as a mediator of voluntary and excessive alcohol consumption. KCa2.3 channels represent a promising novel target in the pharmacogenetic treatment of alcohol and drug addiction.
Assuntos
Alcoolismo/genética , Canais de Potássio Ativados por Cálcio de Condutância Baixa/genética , Transtornos Relacionados ao Uso de Substâncias/genética , Alcoolismo/etiologia , Análise de Variância , Animais , Apamina/toxicidade , Depressores do Sistema Nervoso Central/toxicidade , Comportamento de Escolha/efeitos dos fármacos , Biologia Computacional , Condicionamento Operante/efeitos dos fármacos , Relação Dose-Resposta a Droga , Estimulação Elétrica , Etanol/administração & dosagem , Feminino , Humanos , Técnicas In Vitro , Modelos Lineares , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Mutantes , Análise em Microsséries/estatística & dados numéricos , Microinjeções , Núcleo Accumbens/citologia , Núcleo Accumbens/efeitos dos fármacos , Técnicas de Patch-Clamp , Bloqueadores dos Canais de Potássio/toxicidade , Locos de Características Quantitativas , Canais de Potássio Ativados por Cálcio de Condutância Baixa/classificação , Canais de Potássio Ativados por Cálcio de Condutância Baixa/metabolismo , Transmissão Sináptica/efeitos dos fármacos , Transmissão Sináptica/genéticaRESUMO
Alcohol use disorders (AUDs) are associated with functional and morphological changes in subfields of the prefrontal cortex. Clinical and preclinical evidence indicates that the orbitofrontal cortex (OFC) is critical for controlling impulsive behaviors, representing the value of a predicted outcome, and reversing learned associations. Individuals with AUDs often demonstrate deficits in OFC-dependent tasks, and rodent models of alcohol exposure show that OFC-dependent behaviors are impaired by chronic alcohol exposure. To explore the mechanisms that underlie these impairments, we examined dendritic spine density and morphology, and NMDA-type glutamate receptor expression in the lateral OFC of C57BL/6J mice following chronic intermittent ethanol (CIE) exposure. Western blot analysis demonstrated that NMDA receptors were not altered immediately following CIE exposure or after 7 days of withdrawal. Morphological analysis of basal dendrites of layer II/III pyramidal neurons revealed that dendritic spine density was also not affected immediately after CIE exposure. However, the total density of dendritic spines was significantly increased after a 7-day withdrawal from CIE exposure. The effect of withdrawal on spine density was mediated by an increase in the density of long, thin spines with no change in either stubby or mushroom spines. These data suggest that morphological neuroadaptations in lateral OFC neurons develop during alcohol withdrawal and occur in the absence of changes in the expression of NMDA-type glutamate receptors. The enhanced spine density that follows alcohol withdrawal may contribute to the impairments in OFC-dependent behaviors observed in CIE-treated mice.