RESUMO
RATIONALE: The development and progression of alcohol use disorder (AUD) are widely viewed as maladaptive neuroplasticity. The transmembrane alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptor (AMPAR) regulatory protein γ8 (TARP γ-8) is a molecular mechanism of neuroplasticity that has not been evaluated in AUD or other addictions. OBJECTIVE: To address this gap in knowledge, we evaluated the mechanistic role of TARP γ-8 bound AMPAR activity in the basolateral amygdala (BLA) and ventral hippocampus (vHPC) in the positive reinforcing effects of alcohol, which drive repetitive alcohol use throughout the course of AUD, in male C57BL/6 J mice. These brain regions were selected because they exhibit high levels of TARP γ-8 expression and send glutamate projections to the nucleus accumbens (NAc), which is a key nucleus in the brain reward pathway. METHODS AND RESULTS: Site-specific pharmacological inhibition of AMPARs bound to TARP γ-8 in the BLA via bilateral infusion of the selective negative modulator JNJ-55511118 (0-2 µg/µl/side) significantly decreased operant alcohol self-administration with no effect on sucrose self-administration in behavior-matched controls. Temporal analysis showed that reductions in alcohol-reinforced response rate occurred > 25 min after the onset of responding, consistent with a blunting of the positive reinforcing effects of alcohol in the absence of nonspecific behavioral effects. In contrast, inhibition of TARP γ-8 bound AMPARs in the vHPC selectively decreased sucrose self-administration with no effect on alcohol. CONCLUSIONS: This study reveals a novel brain region-specific role of TARP γ-8 bound AMPARs as a molecular mechanism of the positive reinforcing effects of alcohol and non-drug rewards.
Assuntos
Alcoolismo , Complexo Nuclear Basolateral da Amígdala , Canais de Cálcio , Etanol , Hipocampo , Receptores de AMPA , Sacarose , Animais , Masculino , Camundongos , Alcoolismo/etiologia , Alcoolismo/metabolismo , Complexo Nuclear Basolateral da Amígdala/efeitos dos fármacos , Complexo Nuclear Basolateral da Amígdala/metabolismo , Canais de Cálcio/metabolismo , Etanol/administração & dosagem , Etanol/farmacologia , Ácido Glutâmico/metabolismo , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Locomoção/efeitos dos fármacos , Camundongos Endogâmicos C57BL , Plasticidade Neuronal/efeitos dos fármacos , Núcleo Accumbens/metabolismo , Receptores de AMPA/antagonistas & inibidores , Receptores de AMPA/metabolismo , Reforço Psicológico , Recompensa , Sacarose/administração & dosagem , Sacarose/farmacologiaRESUMO
BACKGROUND: A prominent therapeutic indication for alcohol use disorder (AUD) is reduction in chronic repetitive alcohol use. Glutamate α-Amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptors (AMPARs) regulate chronic alcohol self-administration in preclinical models. Recent evidence indicates that the expression and function of AMPARs require the transmembrane AMPAR regulatory protein γ-8 (TARP γ-8). This study evaluated the preclinical efficacy of JNJ-55511118, a novel, selective, high-affinity inhibitor of TARP γ-8-bound AMPARs, in reducing chronic operant alcohol self-administration. METHODS: Separate groups of male and female C57BL/6J mice (n = 8/sex/group) were trained to lever press for sweetened alcohol (9% v/v + sucrose 2% w/v) or sucrose only (2% w/v) in operant conditioning chambers using an FR-4 schedule of reinforcement. After a 40-day baseline, JNJ-55511118 (0, 1, and 10 mg/kg, p.o.) was administered in randomized order 1 h before self-administration sessions. Parameters of operant behavior including response rate, total reinforcers, and head entries in the drinking troughs were computer recorded. RESULTS: During baseline, responding to alcohol, but not sucrose, was greater in female than male mice. In male mice, both doses of JNJ-55511118 decreased multiple parameters of alcohol self-administration but did not reduce behavior-matched sucrose-only self-administration. JNJ-55511118 had no effect on sweetened alcohol or sucrose self-administration in female mice. Subsequent tests of motor function showed that the lowest effective dose of JNJ-55511118 (1 mg/kg) had no effect on open-field activity in male mice. CONCLUSIONS: This study shows for the first time that TARP γ-8-bound AMPARs regulate a behavioral pathology associated with addiction. The preclinical efficacy of JNJ-55511118 in reducing alcohol self-administration in male mice suggests that inhibition of TARP γ-8-bound AMPARs is a novel and highly significant neural target for developing medications to treat AUD and other forms of addiction.
Assuntos
Consumo de Bebidas Alcoólicas/tratamento farmacológico , Benzimidazóis/farmacologia , Canais de Cálcio/efeitos dos fármacos , Canais de Cálcio/fisiologia , Etanol/administração & dosagem , Receptores de AMPA/antagonistas & inibidores , Animais , Feminino , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Atividade Motora/efeitos dos fármacos , Receptores de AMPA/química , Fatores Sexuais , Sacarose/administração & dosagemRESUMO
Addiction is viewed as maladaptive glutamate-mediated neuroplasticity that is regulated, in part, by calcium-permeable AMPA receptor (CP-AMPAR) activity. However, the contribution of CP-AMPARs to alcohol-seeking behavior remains to be elucidated. We evaluated CP-AMPAR activity in the basolateral amygdala (BLA) as a potential target of alcohol that also regulates alcohol self-administration in C57BL/6J mice. Operant self-administration of sweetened alcohol increased spontaneous EPSC frequency in BLA neurons that project to the nucleus accumbens as compared with behavior-matched sucrose controls indicating an alcohol-specific upregulation of synaptic activity. Bath application of the CP-AMPAR antagonist NASPM decreased evoked EPSC amplitude only in alcohol self-administering mice indicating alcohol-induced synaptic insertion of CP-AMPARs in BLA projection neurons. Moreover, NASPM infusion in the BLA dose-dependently decreased the rate of operant alcohol self-administration providing direct evidence for CP-AMPAR regulation of alcohol reinforcement. As most CP-AMPARs are GluA1-containing, we asked if alcohol alters the activation state of GluA1-containing AMPARs. Immunocytochemistry results showed elevated GluA1-S831 phosphorylation in the BLA of alcohol as compared with sucrose mice. To investigate mechanistic regulation of alcohol self-administration by GluA1-containing AMPARs, we evaluated the necessity of GluA1 trafficking using a TET-ON AAV encoding a dominant-negative GluA1 c-terminus (GluA1ct) that blocks activity-dependent synaptic delivery of native GluA1-containing AMPARs. GluA1ct expression in the BLA reduced alcohol self-administration with no effect on sucrose controls. These results show that CP-AMPAR activity and GluA1 trafficking in the BLA mechanistically regulate the reinforcing effects of sweetened alcohol. Pharmacotherapeutic targeting these mechanisms of maladaptive neuroplasticity may aid medical management of alcohol use disorder.
Assuntos
Alcoolismo/metabolismo , Tonsila do Cerebelo/metabolismo , Receptores de AMPA/metabolismo , Animais , Complexo Nuclear Basolateral da Amígdala/metabolismo , Cálcio/metabolismo , Canais de Cálcio , Etanol , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Núcleo Accumbens/efeitos dos fármacos , Fosforilação , Reforço Psicológico , Autoadministração , Transdução de Sinais/efeitos dos fármacos , Sacarose/administração & dosagemRESUMO
Glycogen synthase kinase 3 (GSK-3) is a constitutively active serine-threonine kinase that regulates numerous signaling pathways and has been implicated in neurodegenerative and neuropsychiatric diseases. Alcohol exposure increases GSK-3ß (ser9) phosphorylation (pGSK-3ß); however, few studies have investigated whether GSK-3 regulates the positive reinforcing effects of alcohol, which drive repetitive drug use. To address this goal, male C57BL/6J mice were trained to lever press on a fixed-ratio 4 schedule of sweetened alcohol or sucrose-only reinforcement in operant conditioning chambers. The GSK-3 inhibitor CHIR 99021 (0-10 mg/kg, i.p.) was injected 45 minutes prior to self-administration sessions. After completion of the self-administration dose-effect curve, potential locomotor effects of the GSK-3 inhibitor were assessed. To determine molecular efficacy, CHIR 99021 (10 mg/kg, i.p.) was evaluated on pGSK-3ß, GSK-3ß, protein interacting with C kinase (PICK1), and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor GluA2 subunit protein expression in amygdala, nucleus accumbens (NAcb), and frontal cortex. Results showed that CHIR 99021 (10 mg/kg) dose-dependently increased alcohol reinforced responding with no effect on sucrose self-administration or locomotor activity. CHIR 99021 (10 mg/kg) significantly decreased pGSK-3ß expression in all brain regions tested, reduced PICK1 and increased GluA2 total expression only in the NAcb. We conclude that GSK-3 inhibition increased the reinforcing effects of alcohol in mice. This was associated with reduced pGSK-3ß and PICK1, and increased GluA2 expression. Given prior results showing that AMPA receptor activity regulates alcohol self-administration, we propose that signaling through the GSK-3/PICK1/GluA2 molecular pathway drives the positive reinforcing effects of the drug, which are required for abuse liability.
Assuntos
Consumo de Bebidas Alcoólicas/metabolismo , Condicionamento Operante/efeitos dos fármacos , Quinase 3 da Glicogênio Sintase/metabolismo , Tonsila do Cerebelo/metabolismo , Animais , Encéfalo/metabolismo , Etanol/administração & dosagem , Glicogênio Sintase Quinase 3 beta/metabolismo , Inibição Psicológica , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Núcleo Accumbens/metabolismo , Fosforilação/efeitos dos fármacos , Reforço Psicológico , Recompensa , Autoadministração , Transdução de Sinais/efeitos dos fármacosRESUMO
The central nucleus of the amygdala plays a significant role in alcohol use and other affective disorders; however, the genetically-defined neuronal subtypes and projections that govern these behaviors are not well known. Here we show that neurotensin neurons in the central nucleus of the amygdala of male mice are activated by in vivo ethanol consumption and that genetic ablation of these neurons decreases ethanol consumption and preference in non-ethanol-dependent animals. This ablation did not impact preference for sucrose, saccharin, or quinine. We found that the most robust projection of the central amygdala neurotensin neurons was to the parabrachial nucleus, a brain region known to be important in feeding behaviors, conditioned taste aversion, and alarm. Optogenetic stimulation of projections from these neurons to the parabrachial nucleus is reinforcing, and increases ethanol drinking as well as consumption of sucrose and saccharin solutions. These data suggest that this central amygdala to parabrachial nucleus projection influences the expression of reward-related phenotypes and is a novel circuit promoting consumption of ethanol and palatable fluids.SIGNIFICANCE STATEMENT Alcohol use disorder (AUD) is a major health burden worldwide. Although ethanol consumption is required for the development of AUD, much remains unknown regarding the underlying neural circuits that govern initial ethanol intake. Here we show that ablation of a population of neurotensin-expressing neurons in the central amygdala decreases intake of and preference for ethanol in non-dependent animals, whereas the projection of these neurons to the parabrachial nucleus promotes consumption of ethanol as well as other palatable fluids.
Assuntos
Consumo de Bebidas Alcoólicas/psicologia , Núcleo Central da Amígdala/fisiologia , Preferências Alimentares/fisiologia , Neurônios/fisiologia , Neurotensina/fisiologia , Animais , Ansiedade/psicologia , Núcleo Central da Amígdala/citologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Atividade Motora/fisiologia , Vias Neurais/citologia , Vias Neurais/fisiologia , Optogenética , Núcleos Parabraquiais/citologia , Núcleos Parabraquiais/fisiologia , Técnicas de Patch-Clamp , Recompensa , Edulcorantes , Paladar/fisiologiaRESUMO
Alzheimer's disease (AD) is a progressive neurodegenerative disorder that represents the most common cause of dementia in the United States. Although the link between alcohol use and AD has been studied, preclinical research has potential to elucidate neurobiological mechanisms that underlie this interaction. This study was designed to test the hypothesis that nondependent alcohol drinking exacerbates the onset and magnitude of AD-like neural and behavioral pathology. We first evaluated the impact of voluntary 24-h, two-bottle choice home-cage alcohol drinking on the prefrontal cortex and amygdala neuroproteome in C57BL/6J mice and found a striking association between alcohol drinking and AD-like pathology. Bioinformatics identified the AD-associated proteins MAPT (Tau), amyloid beta precursor protein (APP), and presenilin-1 (PSEN-1) as the main modulators of alcohol-sensitive protein networks that included AD-related proteins that regulate energy metabolism (ATP5D, HK1, AK1, PGAM1, CKB), cytoskeletal development (BASP1, CAP1, DPYSL2 [CRMP2], ALDOA, TUBA1A, CFL2, ACTG1), cellular/oxidative stress (HSPA5, HSPA8, ENO1, ENO2), and DNA regulation (PURA, YWHAZ). To address the impact of alcohol drinking on AD, studies were conducted using 3xTg-AD mice that express human MAPT, APP, and PSEN-1 transgenes and develop AD-like brain and behavioral pathology. 3xTg-AD and wild-type mice consumed alcohol or saccharin for 4 months. Behavioral tests were administered during a 1-month alcohol-free period. Alcohol intake induced AD-like behavioral pathologies in 3xTg-AD mice including impaired spatial memory in the Morris Water Maze, diminished sensorimotor gating as measured by prepulse inhibition, and exacerbated conditioned fear. Multiplex immunoassay conducted on brain lysates showed that alcohol drinking upregulated primary markers of AD pathology in 3xTg-AD mice: Aß 42/40 ratio in the lateral entorhinal and prefrontal cortex and total Tau expression in the lateral entorhinal cortex, medial prefrontal cortex, and amygdala at 1-month post alcohol exposure. Immunocytochemistry showed that alcohol use upregulated expression of pTau (Ser199/Ser202) in the hippocampus, which is consistent with late-stage AD. According to the NIA-AA Research Framework, these results suggest that alcohol use is associated with Alzheimer's pathology. Results also showed that alcohol use was associated with a general reduction in Akt/mTOR signaling via several phosphoproteins (IR, IRS1, IGF1R, PTEN, ERK, mTOR, p70S6K, RPS6) in multiple brain regions including hippocampus and entorhinal cortex. Dysregulation of Akt/mTOR phosphoproteins suggests alcohol may target this pathway in AD progression. These results suggest that nondependent alcohol drinking increases the onset and magnitude of AD-like neural and behavioral pathology in 3xTg-AD mice.
Assuntos
Consumo de Bebidas Alcoólicas/metabolismo , Consumo de Bebidas Alcoólicas/psicologia , Encéfalo/patologia , Proteínas tau/metabolismo , Consumo de Bebidas Alcoólicas/patologia , Doença de Alzheimer/genética , Doença de Alzheimer/patologia , Doença de Alzheimer/psicologia , Precursor de Proteína beta-Amiloide/genética , Animais , Comportamento Animal , Modelos Animais de Doenças , Chaperona BiP do Retículo Endoplasmático , Camundongos Transgênicos , Proteínas tau/genéticaRESUMO
Metabotropic glutamate receptor subtype-5 (mGluR5) activity regulates a variety of behavioral pathologies associated with alcohol addiction. The main goal of this study was to determine if mGluR5 regulates the induction of ethanol-induced locomotor sensitization, which is a model of experience-dependent plasticity following initial exposure to drugs of abuse. The extracellular signal-regulated kinase (ERK1/2) pathway is downstream of mGluR5 and implicated in alcohol addiction; however, its role in sensitization remains unexplored. We sought to determine if mGluR5-mediated changes in ethanol-induced sensitization are associated with changes in ERK1/2 phosphorylation (pERK1/2) in specific brain regions. Adult male DBA/2 J mice were tested for acute locomotor response to ethanol (0 or 2 g/kg, IP) followed by a 9-day induction period in which the mGluR5 antagonist MPEP (0 or 30 mg/kg, IP) was administered prior to ethanol (0 or 2.5 g/kg, IP). One day later, ethanol (2 g/kg) produced a robust within- and between-group increase in locomotor activity, indicating sensitization in mice that received MPEP (0 mg/kg) during induction. MPEP (30 mg/kg) treatment during induction resulted in locomotor response to ethanol (2 g/kg) challenge that was equivalent to an acute response, indicating full blockade of sensitization. Sensitization was associated with increased pERK1/2 immunoreactivity (IR) in nucleus accumbens shell (AcbSh) and a reduction in lateral habenula (LHb), both of which were blocked by MPEP treatment during induction. Sensitization was also associated with mGluR5-independent increases in pERK1/2 IR in the nucleus accumbens core and decreases in the dentate gyrus and lateral septum. These data indicate that mGluR5 activity is required for the induction of ethanol locomotor sensitization and associated changes in ERK1/2 phosphorylation in the AcbSh and LHb, which raises the hypothesis that mGluR5-mediated cell signaling in these brain regions may mediate the induction of sensitization. Elucidating mechanisms of sensitization may increase understanding of how ethanol hijacks behavioral functions during the development of addiction.
Assuntos
Depressores do Sistema Nervoso Central/farmacologia , Sensibilização do Sistema Nervoso Central , Etanol/farmacologia , MAP Quinases Reguladas por Sinal Extracelular , Habenula , Núcleo Accumbens , Receptor de Glutamato Metabotrópico 5/metabolismo , Transdução de Sinais , Animais , Sensibilização do Sistema Nervoso Central/efeitos dos fármacos , Antagonistas de Aminoácidos Excitatórios/farmacologia , MAP Quinases Reguladas por Sinal Extracelular/efeitos dos fármacos , MAP Quinases Reguladas por Sinal Extracelular/metabolismo , Habenula/efeitos dos fármacos , Habenula/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos DBA , Núcleo Accumbens/efeitos dos fármacos , Núcleo Accumbens/metabolismo , Fosforilação/efeitos dos fármacos , Piridinas/farmacologia , Receptor de Glutamato Metabotrópico 5/antagonistas & inibidores , Transdução de Sinais/efeitos dos fármacosRESUMO
RATIONALE: There is a clear need for discovery of effective medications to treat behavioral pathologies associated with alcohol addiction, such as chronic drinking. OBJECTIVE: The goal of this preclinical study was to assess effects of chronic alcohol drinking on the nucleus accumbens (NAcb) proteome to identify and validate novel targets for medications development. MATERIALS AND METHODS: Two-dimensional difference in-gel electrophoresis (2D-DIGE) with matrix-assisted laser desorption ionization tandem time-of-flight (MALDI-TOF/TOF) was used to assess effects of chronic voluntary home-cage (24-h access) alcohol drinking on the NAcb proteome of C57BL/6J mice. To extend these findings to a model of alcohol self-administration and reinforcement, we investigated potential regulation of the positive reinforcing effects of alcohol by the target protein glutathione S-transferase Pi 1 (GSTP1) using a pharmacological inhibition strategy in mice trained to self-administer alcohol or sucrose. RESULTS: Expression of 52 unique proteins in the NAcb was changed by chronic alcohol drinking relative to water control (23 upregulated, 29 downregulated). Ingenuity Pathway Analysis showed that alcohol drinking altered an array of protein networks associated with neurological and psychological disorders, molecular and cellular functions, and physiological systems and development. DAVID functional annotation analysis identified 9 proteins (SNCA, GSTP1, PRDX3, PPP3R1, EIF5A, PHB, PEBP1/RKIP, GAPDH, AND SOD1) that were significantly overrepresented in a functional cluster that included the Gene Ontology categories "response to alcohol" and "aging." Immunoblots confirmed changes in Pebp1 (RKIP) and GSTP1 in NAcb with no change in amygdala or frontal cortex, suggesting anatomical specificity. Systemic inhibition of GSTP1 with Ezatiostat (0-30 mg/kg, i.p.) dose-dependently reduced the reinforcing effects of alcohol as measured by operant self-administration, in the absence of motor effects. Sucrose self-administration was also reduced but in a manner associated with nonspecific motor inhibition. CONCLUSIONS: Protein expression profiling identified an array of proteins and networks in the NAcb, including GSTP1, that are novel molecular targets of chronic alcohol drinking. Pharmacological inhibition of GSTP1 significantly reduced the positive reinforcing effects of alcohol, which regulate repetitive use and abuse liability. The observation that this protein was both upregulated after chronic drinking and that its inhibition could modulate the reinforcing properties of alcohol suggests that it is a key target for alcohol-related pathologies. Proteomic strategies combined with specific preclinical models has potential to identify and validate novel targets of alcohol that may be useful in the medical management of alcohol addiction.
Assuntos
Consumo de Bebidas Alcoólicas/metabolismo , Etanol/administração & dosagem , Núcleo Accumbens/efeitos dos fármacos , Núcleo Accumbens/metabolismo , Proteoma/metabolismo , Consumo de Bebidas Alcoólicas/genética , Consumo de Bebidas Alcoólicas/psicologia , Animais , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Proteoma/genética , Proteômica/métodos , Reforço Psicológico , Autoadministração/métodos , Sacarose/administração & dosagemRESUMO
Cue-induced reinstatement of alcohol-seeking is a hallmark behavioral pathology of addiction. Evidence suggests that reinstatement (e.g., relapse), may be regulated by cell signaling systems that underlie neuroplasticity. A variety of plasticity events require activation of calcium calmodulin-dependent protein kinase II (CaMKII) in components of the reward pathway, such as the nucleus accumbens and amygdala. We sought to determine if cue-induced reinstatement of alcohol-seeking behavior is associated with changes in the activation state (e.g., phosphorylation) of CaMKII-T286. Male C57BL/6J mice (n=14) were trained to lever press on a fixed-ratio-4 schedule of sweetened alcohol (2% sucrose+9% EtOH) reinforcement. After 14-d of extinction (no cues or reinforcers), mice underwent a response-contingent reinstatement (n=7) vs. an additional day of extinction (n=7). Brains were removed immediately after the test and processed for evaluation of pCaMKII-T286 immunoreactivity (IR). Number of pCaMKII-T286 positive cells/mm2 was quantified from coronal brain sections using Bioquant Image Analysis software. Mice emitted significantly more responses on the alcohol vs. the inactive lever throughout the baseline phase with average alcohol intake of 1.1±0.03g/kg/1-h. During extinction, responses on the alcohol lever decreased to inactive lever levels by day 7. Significant cue-induced reinstatement of alcohol-seeking was observed during a single test with no effects on the inactive lever. Reinstatement was associated with increased pCaMKII-T286 IR specifically in amygdala (LA and BLA), nucleus accumbens (AcbSh), lateral septum, mediodorsal thalamus, and piriform cortex as compared to extinction control. Brain regions showing no change included the dorsal striatum, medial septum, cingulate cortex, habenula, paraventricular thalamus, and ventral hypothalamus. These results show response contingent cue-induced reinstatement of alcohol-seeking behavior is associated with selective increases in pCaMKII-T286 in specific reward- and memory-related brain regions of male C57BL/6J mice. Primary molecular mechanisms of associative learning and memory may regulate relapse in alcohol addiction.
Assuntos
Comportamento Animal/efeitos dos fármacos , Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina/metabolismo , Sinais (Psicologia) , Etanol/administração & dosagem , Recompensa , Animais , Encéfalo/efeitos dos fármacos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , FosforilaçãoRESUMO
BACKGROUND: Despite worldwide consumption of moderate amounts of alcohol, the neural mechanisms that mediate the transition from use to abuse are not fully understood. METHODS: Here, we conducted a high-throughput screen of the amygdala proteome in mice after moderate alcohol drinking (n = 12/group) followed by behavioral studies (n = 6-8/group) to uncover novel molecular mechanisms of the positive reinforcing properties of alcohol that strongly influence the development of addiction. RESULTS: Two-dimensional difference in-gel electrophoresis with matrix assisted laser desorption ionization tandem time-of-flight identified 29 differentially expressed proteins in the amygdala of nondependent C57BL/6J mice following 24 days of alcohol drinking. Alcohol-sensitive proteins included calcium/calmodulin-dependent protein kinase II alpha (CaMKIIα) and a network of functionally linked proteins that regulate neural plasticity and glutamate-mediated synaptic activity. Accordingly, alcohol drinking increased α-amino-3-hydroxy-5-methyl-4-isooxazole receptor (AMPAR) in central amygdala (CeA) and phosphorylation of AMPAR GluA1 subunit at a CaMKII locus (GluA1-Ser831) in CeA and lateral amygdala. Further, CaMKIIα-Thr286 and GluA1-Ser831 phosphorylation was increased in CeA and lateral amygdala of mice that lever-pressed for alcohol versus the nondrug reinforcer sucrose. Mechanistic studies showed that targeted pharmacologic inhibition of amygdala CaMKII or AMPAR activity specifically inhibited the positive reinforcing properties of alcohol but not sucrose. CONCLUSIONS: Moderate alcohol drinking increases the activity and function of plasticity-linked protein networks in the amygdala that regulate the positive reinforcing effects of the drug. Given the prominence of positive reinforcement in the etiology of addiction, we propose that alcohol-induced adaptations in CaMKIIα and AMPAR signaling in the amygdala may serve as a molecular gateway from use to abuse.
Assuntos
Consumo de Bebidas Alcoólicas/efeitos adversos , Tonsila do Cerebelo/metabolismo , Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina/metabolismo , Etanol/farmacologia , Receptores de AMPA/metabolismo , Animais , Ácido Glutâmico/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Plasticidade Neuronal/efeitos dos fármacos , Fosforilação/efeitos dos fármacos , Proteoma/metabolismo , Transdução de Sinais/efeitos dos fármacosRESUMO
Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) is a multifunctional enzyme that is required for synaptic plasticity and has been proposed to be a primary molecular component of the etiology of alcohol addiction. Chronic alcohol intake upregulates CaMKIIα protein expression in reward-related brain regions including the amygdala and nucleus accumbens, and CaMKIIα activity in the amygdala is required for the positive reinforcing effects of alcohol, suggesting this system promotes consumption in the early stages of alcohol addiction. Alternatively, the medial prefrontal cortex (mPFC) is known to inhibit limbic activity via CaMKII-dependent excitatory projections and may, therefore, enable top-down regulation of motivation. Here we sought to remove that regulatory control by site-specifically inhibiting CaMKII activity in the mPFC, and measured effects on the positive reinforcing effects of sweetened alcohol in C57BL/6J mice. Infusion of the CAMKII inhibitor KN-93 (0-10.0 µg) in the mPFC primarily increased alcohol+sucrose reinforced response rate in a dose- and time-dependent manner. KN-93 infusion reduced response rate in behavior-matched sucrose-only controls. Importantly, potentiation of operant responding for sweetened alcohol occurred immediately after infusion, at a time during which effects on sucrose responding were not observed, and persisted through the session. These results suggest that endogenous CaMKII activity in the mPFC exerts inhibitory control over the positive reinforcing effects of alcohol. Downregulation of CaMKII signaling in the mPFC might contribute to escalated alcohol use.
Assuntos
Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina/antagonistas & inibidores , Depressores do Sistema Nervoso Central/administração & dosagem , Sacarose Alimentar , Etanol/administração & dosagem , Córtex Pré-Frontal/efeitos dos fármacos , Reforço Psicológico , Transtornos Relacionados ao Uso de Álcool/tratamento farmacológico , Transtornos Relacionados ao Uso de Álcool/enzimologia , Animais , Benzilaminas/farmacologia , Proteína Quinase Tipo 2 Dependente de Cálcio-Calmodulina/metabolismo , Modelos Animais de Doenças , Relação Dose-Resposta a Droga , Masculino , Camundongos Endogâmicos C57BL , Córtex Pré-Frontal/enzimologia , Inibidores de Proteínas Quinases/farmacologia , Autoadministração , Sulfonamidas/farmacologia , TempoRESUMO
RATIONALE: Extracellular-signal regulated protein kinase (ERK1/2) is activated by ethanol in reward-related brain regions. Accordingly, systemic inhibition of ERK1/2 potentiates ethanol reinforcement. However, the brain region(s) that mediate this effect are unknown. OBJECTIVE: This study aims to pharmacologically inhibit ERK1/2 in the medial prefrontal cortex (PFC), nucleus accumbens (NAC), and amygdala (AMY) prior to ethanol or sucrose self-administration, and evaluate effects of operant ethanol self-administration on ERK1/2 phosphorylation (pERK1/2). METHODS: Male C57BL/6J mice were trained to lever press on a fixed-ratio-4 schedule of 9% ethanol + 2% sucrose (ethanol) or 2% sucrose (sucrose) reinforcement. Mice were sacrificed immediately after the 30th self-administration session and pERK1/2 immunoreactivity was quantified in targeted brain regions. Additional groups of mice were injected with SL 327 (0-1.7 µg/side) in PFC, NAC, or AMY prior to self-administration. RESULTS: pERK1/2 immunoreactivity was significantly increased by operant ethanol (g/kg = 1.21 g/kg; BAC = 54.9 mg/dl) in the PFC, NAC (core and shell), and AMY (central nucleus) as compared to sucrose. Microinjection of SL 327 (1.7 µg) into the PFC selectively increased ethanol self-administration. Intra-NAC injection of SL 327 had no effect on ethanol- but suppressed sucrose-reinforced responding. Intra-AMY microinjection of SL 327 had no effect on either ethanol- or sucrose-reinforced responding. Locomotor activity was unaffected under all conditions. CONCLUSIONS: Operant ethanol self-administration increases pERK1/2 activation in the PFC, NAC, and AMY. However, ERK1/2 activity only in the PFC mechanistically regulates ethanol self-administration. These data suggest that ethanol-induced activation of ERK1/2 in the PFC is a critical pharmacological effect that mediates the reinforcing properties of the drug.
Assuntos
Tonsila do Cerebelo/efeitos dos fármacos , Depressores do Sistema Nervoso Central/administração & dosagem , Etanol/administração & dosagem , MAP Quinases Reguladas por Sinal Extracelular/antagonistas & inibidores , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Núcleo Accumbens/efeitos dos fármacos , Córtex Pré-Frontal/efeitos dos fármacos , Aminoacetonitrila/análogos & derivados , Aminoacetonitrila/farmacologia , Tonsila do Cerebelo/metabolismo , Animais , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Depressores do Sistema Nervoso Central/farmacologia , Condicionamento Operante , Etanol/farmacologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Atividade Motora/efeitos dos fármacos , Núcleo Accumbens/metabolismo , Fosforilação/efeitos dos fármacos , Córtex Pré-Frontal/metabolismo , Inibidores de Proteases/farmacologia , Reforço Psicológico , Recompensa , AutoadministraçãoRESUMO
The antiepileptic drug levetiracetam (LEV) is a potential treatment for alcohol use disorders, yet few preclinical studies exist on its effects in animal models relevant to drug or alcohol abuse. We investigated the effects of LEV on locomotor stimulation following acute and repeated administration of alcohol or cocaine and on alcohol- and cocaine-mediated changes in responding for brain stimulation reward (BSR) in C57BL/6J mice. LEV alone (10.0-100.0 mg/kg intraperitoneally) had no significant effect on locomotor activity or intracranial self-stimulation. Pretreatment with LEV reduced acute locomotor stimulation by 2.0 g/kg alcohol, attenuated the development of locomotor sensitization to alcohol with repeated exposure, and produced a shift in the dose-response curve for alcohol on BSR threshold without affecting maximum operant response rate (MAX). Conversely, LEV pretreatment enhanced both acute locomotor stimulation by 15 mg/kg cocaine and development of locomotor sensitization following repeated exposure and produced a leftward shift in the dose-response curve for cocaine on BSR threshold without affecting MAX. Electrophysiological recordings in vitro showed that LEV reduced excitatory currents in both ventral tegmental area (VTA) dopamine neurons and nucleus accumbens (NAc) medium spiny neurons, consistent with a presynaptic effect. The opposite effects of LEV pretreatment on alcohol- and cocaine-related behaviors may predict its clinical utility in the treatment of patients with alcohol, but not psychostimulant abuse disorders.
Assuntos
Cocaína/agonistas , Etanol/antagonistas & inibidores , Atividade Motora/efeitos dos fármacos , Piracetam/análogos & derivados , Autoestimulação/efeitos dos fármacos , Animais , Anticonvulsivantes/farmacologia , Depressores do Sistema Nervoso Central/antagonistas & inibidores , Depressores do Sistema Nervoso Central/farmacologia , Sensibilização do Sistema Nervoso Central/efeitos dos fármacos , Cocaína/farmacologia , Inibidores da Captação de Dopamina/agonistas , Inibidores da Captação de Dopamina/farmacologia , Neurônios Dopaminérgicos/efeitos dos fármacos , Neurônios Dopaminérgicos/fisiologia , Relação Dose-Resposta a Droga , Interações Medicamentosas , Etanol/farmacologia , Potenciais Pós-Sinápticos Excitadores/efeitos dos fármacos , Levetiracetam , Masculino , Camundongos , Neurônios/efeitos dos fármacos , Neurônios/fisiologia , Núcleo Accumbens/efeitos dos fármacos , Núcleo Accumbens/fisiologia , Piracetam/farmacologia , Área Tegmentar Ventral/efeitos dos fármacos , Área Tegmentar Ventral/fisiologiaRESUMO
BACKGROUND: Systemic modulation of Group I and II metabotropic glutamate receptors (mGluRs) regulate ethanol self-administration in a variety of animal models. Although these receptors are expressed in reward-related brain regions, the anatomical specificity of their functional involvement in ethanol self-administration remains to be characterized. This study sought to evaluate the functional role of Group I (mGluR5) and Group II (mGluR2/3) in mesocorticolimbic brain regions in ethanol self-administration. METHODS: Alcohol-preferring (P) rats, a genetic model of high alcohol drinking, were trained to self-administer ethanol (15% v/v) versus water in operant conditioning chambers. Effects of brain site-specific infusion of the mGluR5 antagonist 2-methyl-6-(phenylethynyl)pyridine hydrochloride (MPEP) and the mGluR2/3 agonist were then assessed on the maintenance of self-administration. RESULTS: Microinjection of the mGluR5 antagonist MPEP in the nucleus accumbens reduced ethanol self-administration at a dose that did not alter locomotor activity. By contrast, infusion of the mGluR2/3 agonist LY379268 in the nucleus accumbens reduced self-administration and produced nonspecific reductions in locomotor activity. The mGluR5 involvement showed anatomical specificity as evidenced by lack of effect of MPEP infusion in the dorsomedial caudate or medial prefrontal cortex on ethanol self-administration. To determine reinforcer specificity, P-rats were trained to self-administer sucrose (.4% w/v) versus water, and effects of intra-accumbens MPEP were tested. The MPEP did not alter sucrose self-administration or motor behavior. CONCLUSIONS: These results suggest that mGluR5 activity specifically in the nucleus accumbens is required for the maintenance of ethanol self-administration in individuals with genetic risk for high alcohol consumption.
Assuntos
Consumo de Bebidas Alcoólicas/genética , Depressores do Sistema Nervoso Central/administração & dosagem , Etanol/administração & dosagem , Núcleo Accumbens/metabolismo , Receptores de Glutamato Metabotrópico/metabolismo , Consumo de Bebidas Alcoólicas/fisiopatologia , Consumo de Bebidas Alcoólicas/psicologia , Aminoácidos/farmacologia , Análise de Variância , Animais , Animais Recém-Nascidos , Compostos Bicíclicos Heterocíclicos com Pontes/farmacologia , Condicionamento Operante/efeitos dos fármacos , Condicionamento Operante/fisiologia , Relação Dose-Resposta a Droga , Fármacos Atuantes sobre Aminoácidos Excitatórios/farmacologia , Preferências Alimentares/efeitos dos fármacos , Masculino , Microinjeções/métodos , Atividade Motora/efeitos dos fármacos , Atividade Motora/genética , Núcleo Accumbens/efeitos dos fármacos , Piridinas/farmacologia , Ratos , Receptor de Glutamato Metabotrópico 5 , Esquema de Reforço , Autoadministração/métodos , Sacarose/administração & dosagem , Edulcorantes/administração & dosagemRESUMO
BACKGROUND: Pleasure and reward are critical features of alcohol drinking that are difficult to measure in animal studies. Intracranial self-stimulation (ICSS) is a behavioral method for studying the effects of drugs directly on the neural circuitry that underlies brain reward. These experiments had 2 objectives: first, to establish the effects of alcohol on ICSS responding in the C57Bl6/J (C57) and DBA2/J (DBA) mouse strains; and second, to compare these effects to those of the psychostimulant cocaine. METHODS: Male C57 and DBA mice were implanted with unipolar stimulating electrodes in the lateral hypothalamus and conditioned to spin a wheel for reinforcement by the delivery of rewarding electrical stimulation (i.e., brain stimulation-reward or BSR). Using the curve-shift method, the BSR threshold (theta(0)) was determined immediately before and after oral gavage with alcohol (0.3, 0.6, 1.0, 1.7 g/kg) or water. Blood alcohol concentration (BAC) was measured to determine the influence of alcohol metabolism on BSR threshold. Separately, mice were administered cocaine (1.0, 3.0, 10.0, 30.0 mg/kg) or saline intraperitoneally. RESULTS: In C57 mice, the 0.6 g/kg dose of alcohol lowered BSR thresholds by about 20%, during the rising (up to 40 mg/dl), but not falling, phase of BAC. When given to the DBA mice, alcohol lowered BSR thresholds over the entire dose range; the largest reduction was by about 50%. Cocaine lowered BSR thresholds in both strains. However, cocaine was more potent in DBA mice than in C57 mice as revealed by a leftward shift in the cocaine dose-response curve. For both alcohol and cocaine, effects on BSR threshold were dissociable from effects on operant response rates. CONCLUSIONS: In C57 and DBA mice, reductions in BSR threshold reflect the ability of alcohol to potentiate the neural mechanisms of brain reward. The DBA mice are more sensitive to the reward-potentiating effects of both alcohol and cocaine, suggesting that there are mouse strain differences in the neural mechanisms of brain reward that can be measured with the ICSS technique.
Assuntos
Encéfalo/efeitos dos fármacos , Cocaína/administração & dosagem , Etanol/administração & dosagem , Recompensa , Autoestimulação/efeitos dos fármacos , Consumo de Bebidas Alcoólicas/genética , Consumo de Bebidas Alcoólicas/psicologia , Animais , Encéfalo/fisiologia , Transtornos Relacionados ao Uso de Cocaína/genética , Transtornos Relacionados ao Uso de Cocaína/psicologia , Condicionamento Operante/efeitos dos fármacos , Condicionamento Operante/fisiologia , Relação Dose-Resposta a Droga , Estimulação Elétrica/métodos , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos DBA , Autoestimulação/fisiologia , Especificidade da EspécieRESUMO
RATIONALE: Extracellular signal-regulated protein kinase (ERK(1/2)) is a member of the mitogen-activated protein kinase (MAPK) signaling pathway and a key molecular target for ethanol (EtOH) and other drugs of abuse. OBJECTIVE: The aim of the study was to assess the role of two MAPK pathways, ERK(1/2) and c-Jun N-terminal kinase (JNK), on the modulation of EtOH and sucrose self-administration. MATERIALS AND METHODS: C57BL/6J mice were trained to lever press on a fixed-ratio 4 schedule with 9% EtOH/2% sucrose, or 2% sucrose, as the reinforcer. In experiments 1 and 2, mice were injected with the MEK(1/2) inhibitor SL 327 (0-100 mg/kg) and the JNK inhibitor AS 6012452 (0-56 mg/kg) prior to self-administration. In experiment 3, SL 327 (0-100 mg/kg) was administered prior to performance on a progressive ratio (PR) schedule of EtOH reinforcement. In experiment 4, SL 327 and AS 601245 were injected 2 h before a locomotor test. RESULTS: SL 327 (30 mg/kg) significantly increased EtOH self-administration without affecting locomotion. Higher doses of SL 327 and AS 601245 reduced EtOH-reinforced responding and locomotor activity. Reductions of both ligands on sucrose self-administration were due to decreases in motor activity. SL 327 pretreatment had no effect on PR responding. CONCLUSIONS: ERK(1/2) activity is more directly involved in modulating the reinforcing properties of EtOH than JNK activity due to its selective potentiation of EtOH-reinforced responding. The specificity of this effect to EtOH self-administration, rather than sucrose self-administration, suggests that the mechanism by which ERK(1/2) increases EtOH-reinforced responding does not generalize to all reinforcing solutions and is not due to increased motivation to consume EtOH.
Assuntos
Consumo de Bebidas Alcoólicas/psicologia , Depressores do Sistema Nervoso Central/administração & dosagem , Condicionamento Operante/efeitos dos fármacos , Etanol/administração & dosagem , MAP Quinases Reguladas por Sinal Extracelular/fisiologia , Proteínas Quinases JNK Ativadas por Mitógeno/fisiologia , Sistema de Sinalização das MAP Quinases , Acetonitrilas/farmacologia , Aminoacetonitrila/análogos & derivados , Aminoacetonitrila/farmacologia , Animais , Comportamento Animal/efeitos dos fármacos , Benzotiazóis/farmacologia , Relação Dose-Resposta a Droga , MAP Quinases Reguladas por Sinal Extracelular/antagonistas & inibidores , Proteínas Quinases JNK Ativadas por Mitógeno/antagonistas & inibidores , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Atividade Motora/efeitos dos fármacos , Reforço Psicológico , Autoadministração , Sacarose/administração & dosagem , Edulcorantes/administração & dosagemRESUMO
INTRODUCTION: Dysregulation of GABAergic inhibition and glutamatergic excitation has been implicated in exaggerated anxiety. Mouse pups emit distress-like ultrasonic vocalizations (USVs) when they are separated from their dam/siblings, and this behavior is reduced by benzodiazepines (BZs) which modulate GABAergic inhibition. The roles of glutamate receptors on USVs remain to be investigated. MATERIALS AND METHODS: We examined the roles of glutamate receptor subtypes on mouse pup USVs using N-methyl-D: -aspartate (NMDA) receptor antagonists with different affinities [dizocilpine (MK-801), memantine, and neramexane] and group II metabotropic glutamate receptor agonist (LY-379268) and antagonist (LY-341495). These effects were compared with classic BZs: flunitrazepam, bromazepam, and chlordiazepoxide. To assess the role of GABA(A) receptor subunits on USVs, drugs that have preferential actions at different GABA(A)-alpha subunits (L-838417 and QH-ii-066) were tested. Seven-day-old CFW mouse pups were separated from their dam and littermates and placed individually on a 19 degrees C test platform for 4 min. Grid crossings and body rolls were measured in addition to USVs. RESULTS: Dizocilpine dose-dependently reduced USVs, whereas memantine and neramexane showed biphasic effects and enhanced USVs at low to moderate doses. The NMDA receptor antagonists increased locomotion. LY-379268 reduced USVs but also suppressed locomotion. All BZs reduced USVs and increased motor incoordination. Neither L-838417 nor QH-ii-066 changed USVs, but both induced motor incoordination. CONCLUSION: Low-affinity NMDA receptor antagonists, but not the high-affinity antagonist, enhanced mouse pup distress calls, which may be reflective of an anxiety-like state. BZs reduced USVs but also induced motor incoordination, possibly mediated by the alpha5 subunit containing GABA(A) receptors.
Assuntos
Ansiedade/psicologia , Privação Materna , Receptores de GABA-A/fisiologia , Receptores de Glutamato Metabotrópico/fisiologia , Receptores de N-Metil-D-Aspartato/fisiologia , Vocalização Animal/efeitos dos fármacos , Animais , Animais Recém-Nascidos , Ansiolíticos/efeitos adversos , Ansiolíticos/farmacologia , Comportamento Animal/efeitos dos fármacos , GABAérgicos/farmacologia , Locomoção/efeitos dos fármacos , Camundongos , Atividade Motora/efeitos dos fármacos , Subunidades Proteicas/fisiologia , Receptores de Glutamato Metabotrópico/agonistas , Receptores de Glutamato Metabotrópico/antagonistas & inibidores , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Espectrografia do Som , Ultrassom , Vocalização Animal/fisiologiaRESUMO
Emerging evidence indicates that specific metabotropic glutamate receptors (mGluRs) modulate ethanol self-administration. In general, inhibition of glutamate transmission through blockade of postsynaptic mGluRs, or activation of presynaptic mGluRs, inhibits ethanol self-administration. The goal of this preclinical study was to further characterize mGluR regulation of ethanol self-administration by examining effects of AMN082, an allosteric positive modulator of presynaptic mGluR7 activity. Separate groups of C57BL/6J male mice were trained to self-administer ethanol or sucrose on a fixed-ratio 4 schedule of reinforcement during 1 h sessions. On test days, mice were pretreated with AMN082 (0, 1.0, 3.0, 5.6, or 10 mg/kg) 30 min prior to self-administration sessions. Functional specificity and activity was examined by testing the effects of AMN082 (0-10 mg/kg) on open-field locomotor activity and HPA axis function as measured by plasma corticosterone levels. AMN082 (10 mg/kg) produced a significant reduction in ethanol and sucrose reinforced responding, and inhibited locomotor activity. Plasma corticosterone levels were significantly increased following AMN082 (5.6 and 10 mg/kg) suggesting a dose-dependent dissociation between the behavioral and hormonal effects of the compound. These data suggest that activation of mGluR7 by AMNO82 produces nonspecific reductions in motivated behavior that are associated with negative effects on motor activity.
Assuntos
Compostos Benzidrílicos/farmacologia , Depressores do Sistema Nervoso Central/antagonistas & inibidores , Depressores do Sistema Nervoso Central/farmacologia , Condicionamento Operante/efeitos dos fármacos , Etanol/antagonistas & inibidores , Etanol/farmacologia , Receptores de Glutamato Metabotrópico/efeitos dos fármacos , Sacarose/antagonistas & inibidores , Sacarose/farmacologia , Animais , Depressores do Sistema Nervoso Central/sangue , Corticosterona/sangue , Interpretação Estatística de Dados , Relação Dose-Resposta a Droga , Etanol/sangue , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Atividade Motora/efeitos dos fármacos , Reforço Psicológico , AutoadministraçãoRESUMO
A significant minority of individuals engages in escalated levels of aggression after consuming moderate doses of alcohol (Alc). Neural modulation of escalated aggression involves altered levels of serotonin (5-HT) and the activity of 5-HT(1B) receptors. The aim of these studies was to determine whether 5-HT(1B) receptors in the dorsal raphé (DRN), orbitofrontal (OFC), and medial prefrontal (mPFC) cortex attenuate heightened aggression and regulate extracellular levels of 5-HT. Male mice were trained to self-administer Alc by performing an operant response that was reinforced with a delivery of 6% Alc. To identify Alc-heightened aggressors, each mouse was repeatedly tested for aggression after consuming either 1.0 g/kg Alc or H2O. Next, a cannula was implanted into either the DRN, OFC, or mPFC, and subsets of mice were tested for aggression after drinking either Alc or H(2)O prior to a microinjection of the 5-HT(1B) agonist, CP-94,253. Additional mice were implanted with a microdialysis probe into the mPFC, through which CP-94,253 was perfused and samples were collected for 5-HT measurement. Approximately 60% of the mice were more aggressive after drinking Alc, confirming the aggression-heightening effects of 1.0 g/kg Alc. Infusion of 1 microg CP-94,253 into the DRN reduced both aggressive and motor behaviors. However, infusion of 1 microg CP-94,253 into the mPFC, but not the OFC, after Alc drinking, increased aggressive behavior. In the mPFC, reverse microdialysis of CP-94,253 increased extracellular levels of 5-HT; levels decreased immediately after the perfusion. This 5-HT increase was attenuated in self-administering mice. These results suggest that 5-HT(1B) receptors in the mPFC may serve to selectively disinhibit aggressive behavior in mice with a history of Alc self-administration.
Assuntos
Agressão/efeitos dos fármacos , Transtornos do Sistema Nervoso Induzidos por Álcool/metabolismo , Etanol/farmacologia , Córtex Pré-Frontal/efeitos dos fármacos , Núcleos da Rafe/efeitos dos fármacos , Receptor 5-HT1B de Serotonina/efeitos dos fármacos , Agressão/fisiologia , Transtornos do Sistema Nervoso Induzidos por Álcool/genética , Transtornos do Sistema Nervoso Induzidos por Álcool/fisiopatologia , Animais , Comportamento Animal/efeitos dos fármacos , Comportamento Animal/fisiologia , Depressores do Sistema Nervoso Central/farmacologia , Condicionamento Operante/efeitos dos fármacos , Condicionamento Operante/fisiologia , Modelos Animais de Doenças , Líquido Extracelular/efeitos dos fármacos , Líquido Extracelular/metabolismo , Masculino , Mesencéfalo/efeitos dos fármacos , Mesencéfalo/metabolismo , Mesencéfalo/fisiopatologia , Camundongos , Microinjeções , Inibição Neural/efeitos dos fármacos , Inibição Neural/fisiologia , Córtex Pré-Frontal/metabolismo , Córtex Pré-Frontal/fisiopatologia , Núcleos da Rafe/metabolismo , Núcleos da Rafe/fisiopatologia , Receptor 5-HT1B de Serotonina/metabolismo , Reforço Psicológico , Serotonina/metabolismo , Agonistas do Receptor de Serotonina/farmacologia , Transmissão Sináptica/efeitos dos fármacos , Transmissão Sináptica/fisiologia , Regulação para Cima/efeitos dos fármacos , Regulação para Cima/fisiologiaRESUMO
BACKGROUND: Emerging evidence indicates that Group I metabotropic glutamate receptors (mGluR1 and mGluR5) differentially regulates ethanol self-administration in several rodent behavioral models. The purpose of this work was to further characterize involvement of Group I mGluRs in the reinforcing effects of ethanol using a progressive ratio schedule of reinforcement. METHODS: Alcohol-preferring (P) rats were trained to self-administer ethanol (15% v/v) versus water on a concurrent schedule of reinforcement, and the effects of the Group I mGluR antagonists were evaluated on progressive ratio performance. The rats were then trained to self-administer sucrose (0.4% w/v) versus water, and the effects of the antagonists were tested on progressive ratio performance. RESULTS: The mGluR1 antagonist, 3,4-dihydro-2H-pyrano[2,3]b quinolin-7-yl (cis-4-methoxycyclohexyl) methanone (JNJ 16259685; 0 to 1 mg/kg) and the mGluR5 antagonist, 6-methyl-2-(phenylethynyl) pyridine (MPEP; 0 to 10 mg/kg) dose-dependently reduced ethanol break point. In separate locomotor activity assessments, the lowest effective dose of JNJ 16259685 (0.3 mg/kg) produced a motor impairment, whereas the lowest effective dose of MPEP (3 mg/kg) did not. Thus, the reduction in ethanol break point by mGluR1 antagonism was probably a result of a motor impairment. JNJ 16259685 (0.3 mg/kg) and MPEP (10 mg/kg) reduced sucrose break point and produced motor impairments. Thus, the reductions in sucrose break point produced by both Group I antagonists were probably because of nonspecific effects on motor activity. CONCLUSIONS: Together, these results suggest that glutamate activity at mGluR5 regulates motivation to self-administer ethanol.