BACKGROUND: Converging experimental data indicate that δ opioid receptors contribute to mediate drug reinforcement processes. Whether their contribution reflects a role in the modulation of drug reward or an implication in conditioned learning, however, has not been explored. In the present study, we investigated the impact of δ receptor gene knockout on reinforced conditioned learning under several experimental paradigms. METHODS: We assessed the ability of δ receptor knockout mice to form drug-context associations with either morphine (appetitive)- or lithium (aversive)-induced Pavlovian place conditioning. We also examined the efficiency of morphine to serve as a positive reinforcer in these mice and their motivation to gain drug injections, with operant intravenous self-administration under fixed and progressive ratio schedules and at two different doses. RESULTS: Mutant mice showed impaired place conditioning in both appetitive and aversive conditions, indicating disrupted context-drug association. In contrast, mutant animals displayed intact acquisition of morphine self-administration and reached breaking-points comparable to control subjects. Thus, reinforcing effects of morphine and motivation to obtain the drug were maintained. CONCLUSION: Collectively, the data suggest that δ receptor activity is not involved in morphine reinforcement but facilitates place conditioning. This study reveals a novel aspect of δ opioid receptor function in addiction-related behaviors.

Sensitivity to the euphoric and locomotor-activating effects of drugs of abuse may contribute to risk for excessive use and addiction. Repeated administration of psychostimulants such as methamphetamine can result in neuroadaptive consequences that manifest behaviorally as a progressive escalation of locomotor activation, termed psychomotor sensitization. The present studies addressed the involvement of specific components of the corticotropin-releasing factor (CRF) system in locomotor activation and psychomotor sensitization induced by methamphetamine (1, 2 mg/kg) by utilizing pharmacological approaches, as well as a series of genetic knockout mice, each deficient for a single component of the CRF system: CRF-R1, CRF-R2, CRF, or the CRF-related peptide Urocortin 1 (Ucn1). CRF-R1 knockout mice did not differ from wild-type mice in sensitization to methamphetamine, and pharmacological blockade of CRF-R1 with CP-154,526 (15, 30 mg/kg) in DBA/2J mice did not selectively attenuate either the acquisition or expression of methamphetamine-induced sensitization. Deletion of either of the endogenous ligands of CRF-R1 (CRF, Ucn1) either enhanced, or had no effect, on methamphetamine-induced sensitization, providing further evidence against a role for CRF-R1 signaling. Interestingly, deletion of CRF-R2 attenuated methamphetamine-induced locomotor activation, elucidating a novel contribution of the CRF system to methamphetamine sensitivity, and suggesting the participation of the endogenous urocortin peptides Ucn2 and Ucn3. Immunohistochemistry for Fos was used to visualize neural activation underlying CRF-R2-dependent sensitivity to methamphetamine, identifying the basolateral and central nuclei of the amygdala as neural substrates involved in this response. Our results support further examination of CRF-R2 involvement in neural processes associated with methamphetamine addiction.

The eponymous term nucleus of Edinger-Westphal (EW) has come to be used to describe two juxtaposed and somewhat intermingled cell groups of the midbrain that differ dramatically in their connectivity and neurochemistry. On one hand, the classically defined EW is the part of the oculomotor complex that is the source of the parasympathetic preganglionic motoneuron input to the ciliary ganglion (CG), through which it controls pupil constriction and lens accommodation. On the other hand, EW is applied to a population of centrally projecting neurons involved in sympathetic, consumptive, and stress-related functions. This terminology problem arose because the name EW has historically been applied to the most prominent cell collection above or between the somatic oculomotor nuclei (III), an assumption based on the known location of the preganglionic motoneurons in monkeys. However, in many mammals, the nucleus designated as EW is not made up of cholinergic, preganglionic motoneurons supplying the CG and instead contains neurons using peptides, such as urocortin 1, with diverse central projections. As a result, the literature has become increasingly confusing. To resolve this problem, we suggest that the term EW be supplemented with terminology based on connectivity. Specifically, we recommend that 1) the cholinergic, preganglionic neurons supplying the CG be termed the Edinger-Westphal preganglionic (EWpg) population and 2) the centrally projecting, peptidergic neurons be termed the Edinger-Westphal centrally projecting (EWcp) population. The history of this nomenclature problem and the rationale for our solutions are discussed in this review.

A functional connection between the circadian timing system and alcohol consumption is suggested by multiple lines of converging evidence. Ethanol consumption perturbs physiological rhythms in hormone secretion, sleep and body temperature, and conversely, genetic and environmental perturbations of the circadian system can alter alcohol intake. A fundamental property of the circadian pacemaker, the endogenous period of its cycle under free-running conditions, was previously shown to differ between selectively bred High- (HAP) and Low- (LAP) Alcohol Preferring replicate 1 mice. To test whether there is a causal relationship between circadian period and ethanol intake, we induced experimental, rather than genetic, variations in free-running period. Male inbred C57Bl/6J mice and replicate 2 male and female HAP2 and LAP2 mice were entrained to light:dark cycles of 26 h or 22 h or remained in a standard 24 h cycle. Upon discontinuation of the light:dark cycle, experimental animals exhibited longer and shorter free-running periods, respectively. Despite robust effects on circadian period and clear circadian rhythms in drinking, these manipulations failed to alter the daily ethanol intake of the inbred strain or selected lines. Likewise, driving the circadian system at long and short periods produced no change in alcohol intake. In contrast with replicate 1 HAP and LAP lines, there was no difference in free-running period between ethanol naïve HAP2 and LAP2 mice. HAP2 mice, however, were significantly more active than LAP2 mice as measured by general home-cage movement and wheel running, a motivated behavior implicating a selection effect on reward systems. Despite a marked circadian regulation of drinking behavior, the free-running and entrained period of the circadian clock does not determine daily ethanol intake.

Brain cell loss has been reported in subjects with alcoholism. However, the molecular mechanisms are unclear. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and monoamine oxidase B (MAO B) reportedly play a role in cellular dysfunction with regards to ethanol exposure. We have recently reported that GAPDH protein expression was increased in the brains of rats fed with ethanol. Furthermore, GAPDH interacts with the transcriptional activator, transforming growth factor-beta-inducible early gene 2 (TIEG2), to augment TIEG2-mediated MAO B activation, resulting in neuronal cell damage due to ethanol exposure. The current study investigates whether the TIEG2-MAO B cascade is also active in the brains of rats fed with ethanol. Ten ethanol-preferring rats were fed with a liquid diet containing ethanol, with increasing amounts of ethanol up to a final concentration of 6.4% representing a final diet containing 36% of calories for 28 days. Ten control rats were fed the liquid diet without ethanol. The expression of TIEG2 protein, MAO B mRNA levels, MAO B catalytic activity, and the levels of anti-apoptotic protein Bcl 2 and apoptotic protein caspase 3 were determined in the prefrontal cortex of the rats. Ethanol significantly increased protein levels of TIEG2, active caspase 3, MAO B mRNA and enzyme activity, but significantly decreased Bcl 2 protein expression compared to control rats. In summary, ethanol increases the TIEG2-MAO B brain cell death cascade in rat brains, suggesting that the TIEG2-MAO B pathway is a novel pathway for brain cell damage resulting from ethanol exposure, and may contribute to chronic alcohol-induced brain damage.

Activation of dopaminergic (DA) neurons of the ventral tegmental area (VTA) by ethanol has been implicated in its rewarding and reinforcing effects. However, studies from our lab demonstrate that acute ethanol enhances GABA release onto VTA-DA neurons via activation of a G protein-coupled receptor, 5-HT2C, and subsequent activation of an intracellular calcium signaling pathway. Utilizing electrophysiological methods, in this chapter we present evidence which attempts to resolve the paradoxical nature of the dual excitatory and inhibitory actions of ethanol on DA neurons. Our results suggest that ethanol-excitation of VTA-DA neurons is bi-phasic and involves interplay of excitatory and inhibitory mechanisms which can fine tune the overall action of ethanol on DA neuron excitability. Overall, these results may provide insight into mechanisms underlying the development of alcohol dependence.

Despite extensive description of the damaging effects of chronic alcohol exposure on brain structure, mechanistic explanations for the observed changes are just emerging. To investigate regional brain changes in protein expression levels following chronic ethanol treatment, one rat per sibling pair of male Wistar rats was exposed to intermittent (14 h/day) vaporized ethanol, the other to air for 26 weeks. At the end of 24 weeks of vapor exposure, the ethanol group had blood ethanol levels averaging 450 mg%, had not experienced a protracted (\textgreater 16 h) withdrawal from ethanol, and revealed only mild evidence of hepatic steatosis. Extracted brains were micro-dissected to isolate the prefrontal cortex (PFC), dorsal striatum (STR), corpus callosum genu (CCg), CC body (CCb), anterior vermis (AV), and anterior dorsal lateral cerebellum (ADLC) for protein analysis with two-dimensional gel electrophoresis. Expression levels for 54 protein spots were significantly different between the ethanol- and air-treated groups. Of these 54 proteins, tandem mass spectroscopy successfully identified 39 unique proteins, the levels of which were modified by ethanol treatment: 13 in the PFC, 7 in the STR, 2 in the CCg, 7 in the CCb, 7 in the AV, and 5 in the ADLC. The functions of the proteins altered by chronic ethanol exposure were predominantly associated with neurotransmitter systems in the PFC and cell metabolism in the STR. Stress response proteins were elevated only in the PFC, AV, and ADLC perhaps supporting a role for frontocerebellar circuitry disruption in alcoholism. Of the remaining proteins, some had functions associated with cytoskeletal physiology (e.g., in the CCb) and others with transcription/translation (e.g., in the ADLC). Considered collectively, all but 4 of the 39 proteins identified in the present study have been previously identified in ethanol gene- and/or protein-expression studies lending support for their role in ethanol-related brain alterations.

C57BL/6J (B6) and DBA/2J (D2) are two of the most commonly used inbred mouse strains in neuroscience research. However, the only currently available mouse genome is based entirely on the B6 strain sequence. Subsequently, oligonucleotide microarray probes are based solely on this B6 reference sequence, making their application for gene expression profiling comparisons across mouse strains dubious due to their allelic sequence differences, including single nucleotide polymorphisms (SNPs). The emergence of next-generation sequencing (NGS) and the RNA-Seq application provides a clear alternative to oligonucleotide arrays for detecting differential gene expression without the problems inherent to hybridization-based technologies. Using RNA-Seq, an average of 22 million short sequencing reads were generated per sample for 21 samples (10 B6 and 11 D2), and these reads were aligned to the mouse reference genome, allowing 16,183 Ensembl genes to be queried in striatum for both strains. To determine differential expression, ‘digital mRNA counting’ is applied based on reads that map to exons. The current study compares RNA-Seq (Illumina GA IIx) with two microarray platforms (Illumina MouseRef-8 v2.0 and Affymetrix MOE 430 2.0) to detect differential striatal gene expression between the B6 and D2 inbred mouse strains. We show that by using stringent data processing requirements differential expression as determined by RNA-Seq is concordant with both the Affymetrix and Illumina platforms in more instances than it is concordant with only a single platform, and that instances of discordance with respect to direction of fold change were rare. Finally, we show that additional information is gained from RNA-Seq compared to hybridization-based techniques as RNA-Seq detects more genes than either microarray platform. The majority of genes differentially expressed in RNA-Seq were only detected as present in RNA-Seq, which is important for studies with smaller effect sizes where the sensitivity of hybridization-based techniques could bias interpretation.

Activation of the dopaminergic (DA) neurons of the ventral tegmental area (VTA) by ethanol has been implicated in its rewarding and reinforcing effects. We previously demonstrated that ethanol enhances GABA release onto VTA-DA neurons via activation of 5-HT2C receptors and subsequent release of calcium from intracellular stores. Here we demonstrate that excitation of VTA-DA neurons by ethanol is limited by an ethanol-enhancement in GABA release. In this study, we performed whole-cell voltage clamp recordings of miniature inhibitory postsynaptic currents (mIPSCs) and cell-attached recordings of action potential firing from VTA-DA neurons in midbrain slices from young Long Evans rats. Acute exposure to ethanol (75 mM) transiently enhanced the firing rate of VTA-DA neurons as well as the frequency of mIPSCs. Simultaneous blockade of both GABA(A) and GABA(B) receptors (Picrotoxin (75 μM) and SCH50911 (20 μM)) disinhibited VTA-DA firing rate whereas a GABA(A) agonist (muscimol, 1 μM) strongly inhibited firing rate. In the presence of picrotoxin, ethanol enhanced VTA-DA firing rate more than in the absence of picrotoxin. Additionally, a sub-maximal concentration of muscimol together with ethanol inhibited VTA-DA firing rate more than muscimol alone. DAMGO (3 μM) inhibited mIPSC frequency but did not block the ethanol-enhancement in mIPSC frequency. DAMGO (1 and 3 μM) had no effect on VTA-DA firing rate. Naltrexone (60 μM) had no effect on basal or ethanol-enhancement of mIPSC frequency. Additionally, naltrexone (20 and 60 μM) did not block the ethanol-enhancement in VTA-DA firing rate. Overall, the present results indicate that the ethanol enhancement in GABA release onto VTA-DA neurons limits the stimulatory effect of ethanol on VTA-DA neuron activity and may have implications for the rewarding properties of ethanol.

Opioid receptors are major actors in pain control and are broadly distributed throughout the nervous system. A major challenge in pain research is the identification of key opioid receptor populations within nociceptive pathways, which control physiological and pathological pain. In particular, the respective contribution of peripheral vs. central receptors remains unclear, and it has not been addressed by genetic approaches. To investigate the contribution of peripheral delta opioid receptors in pain control, we created conditional knockout mice where delta receptors are deleted specifically in peripheral NaV1.8-positive primary nociceptive neurons. Mutant mice showed normal pain responses to acute heat and to mechanical and formalin stimuli. In contrast, mutant animals showed a remarkable increase of mechanical allodynia under both inflammatory pain induced by complete Freund adjuvant and neuropathic pain induced by partial sciatic nerve ligation. In these 2 models, heat hyperalgesia was virtually unchanged. SNC80, a delta agonist administered either systemically (complete Freund adjuvant and sciatic nerve ligation) or into a paw (sciatic nerve ligation), reduced thermal hyperalgesia and mechanical allodynia in control mice. However, these analgesic effects were absent in conditional mutant mice. In conclusion, this study reveals the existence of delta opioid receptor-mediated mechanisms, which operate at the level of NaV1.8-positive nociceptive neurons. Delta receptors in these neurons tonically inhibit mechanical hypersensitivity in both inflammatory and neuropathic pain, and they are essential to mediate delta opioid analgesia under conditions of persistent pain. This delta receptor population represents a feasible therapeutic target to alleviate chronic pain while avoiding adverse central effects. The conditional knockout of delta-opioid receptor in primary afferent NaV1.8 neurons augmented mechanical allodynia in persistent pain models and abolished delta opioid analgesia in these models.

Alcoholism is characterized by a progressive loss of control over ethanol intake. The purpose of this study was to identify transcriptional changes selectively associated with excessive ethanol drinking in dependent mice, as opposed to non-dependent mice maintaining a stable voluntary consumption or mice solely undergoing forced intoxication. We measured expression levels of 106 candidate genes in the extended amygdala, a key brain structure for the development of drug addiction. Cluster analysis identified 17 and 15 genes selectively induced or repressed, respectively, under conditions of excessive drinking. These genes belong to signaling pathways involved in neurotransmission and transcriptional regulation.

Background Opiate abuse is a chronic relapsing disorder and maintaining prolonged abstinence remains a major challenge. Protracted abstinence is characterized by lowered mood and clinical studies show elevated co-morbidity between addiction and depressive disorders. At present, their relationship remains unclear and has been little studied in animal models. Here we investigated emotional alterations during protracted abstinence, in mice with a history of chronic morphine exposure. Methods C57BL6J mice were exposed to a chronic intermittent escalating morphine regimen (20-100mg/kg). Physical dependence (naloxone-precipitated withdrawal), despair-related (tail suspension test) and social behaviors were examined after 1 or 4 weeks of abstinence. Stress hormones and forebrain bioamine levels were analyzed at the end of morphine regimen and after 4 weeks abstinence. Finally, we examined the effects of chronic fluoxetine during abstinence on morphine-induced behavioral deficits. Results Acute naloxone-induced withdrawal was clearly measurable after 1 week, and became undetectable after 4 weeks. In contrast, social and despair-related were unchanged after 1 week, but low sociability and despair-like behavior became significant after 4 weeks. Chronic morphine regimen increased both corticosterone levels and forebrain serotonin turnover, but only serotonergic activity in the dorsal raphe remained impaired after 4 weeks. Remarkably, chronic fluoxetine prevented depressive-like behavioral deficits in 4-week abstinent mice. Conclusions During protracted abstinence, the immediate consequences of morphine exposure attenuate while fluoxetine-sensitive emotional alterations strengthen with time. Our study establishes a direct link between morphine abstinence and depressive-like symptoms, and strongly suggests that serotonin dysfunction represents a main mechanism contributing to mood disorders in opiate abstinence.

Glutamatergic synaptic plasticity in the nucleus accumbens (NAc) is implicated in response to sensitization to psychomotor-stimulating agents, yet ethanol effects here are undefined. We studied the acute in vitro and in vivo effects of ethanol in medium spiny neurons from the shell NAc subregion of slices of C57BL/6 mice by using whole-cell voltage-clamp recordings of α-amino-3-hydroxy-5-methyl-isoxazole-4-propionic acid (AMPA) excitatory postsynaptic current (EPSCs). Synaptic conditioning (low-frequency stimulation with concurrent postsynaptic depolarization) reliably depressed AMPA EPSCs by nearly 30%; this accumbal long-term depression (LTD) was blocked by a nonselective N-methyl-d-aspartate (NMDA) receptor antagonist (dl-2-amino-5-phosphonovaleric acid) and a selective NMDA receptor 2B antagonist [R-(R*,S*)-α-(4-hydroxyphenyl)-β-methyl-4-(phenylmethyl)-1-piperidine propanol]. Acute ethanol exposure inhibited the depression of AMPA EPSCs differentially with increasing concentrations, but this inhibitory action of ethanol was occluded by a D1-selective dopamine receptor agonist. Ethanol dependence was elicited in C57BL/6 mice by two separate 4-day bouts of chronic intermittent ethanol (CIE) vapor exposure. When assessed 24 h after a single bout of in vivo CIE vapor exposure, NAc LTD was absent, and instead NMDA receptor-dependent synaptic potentiation [long-term potentiation (LTP)] was reliably observed. It is noteworthy that both LTP and LTD were completely absent after an extended withdrawal (72 h) after a single 3-day CIE vapor bout. These observations demonstrate that 1) accumbal synaptic depression is mediated by NR2B receptors, 2) accumbal synaptic depression is highly sensitive to both acute and chronic ethanol exposure, and 3) alterations in this synaptic process may constitute a neural adaptation that contributes to the induction and/or expression of ethanol dependence.

Hepatocellular carcinoma (HCC), the primary form of human adult liver malignancy, is a highly aggressive tumor with average survival rates that are currently less than 1 year following diagnosis. Most patients with HCC are diagnosed at an advanced stage, and no efficient marker exists for the prediction of prognosis and/or response(s) to therapy. We have reported previously a high level of [1-(13)C]alanine in an orthotopic HCC using single-voxel hyperpolarized [1-(13)C]pyruvate MRS. In the present study, we implemented a three-dimensional MRSI sequence to investigate this potential hallmark of cellular metabolism in rat livers bearing HCC (n = 7 buffalo rats). In addition, quantitative real-time polymerase chain reaction was used to determine the mRNA levels of lactate dehydrogenase A, nicotinamide adenine (phosphate) dinucleotide dehydrogenase quinone 1 and alanine transaminase. The enzyme levels were significantly higher in tumor than in normal liver tissues within each rat, and were associated with the in vivo MRSI signal of [1-(13)C]alanine and [1-(13)C]lactate after a bolus intravenous injection of [1-(13)C]pyruvate. Histopathological analysis of these tumors confirmed the successful growth of HCC as a nodule in buffalo rat livers, revealing malignancy and hypervascular architecture. More importantly, the results demonstrated that the metabolic fate of [1-(13)C]pyruvate conversion to [1-(13)C]alanine significantly superseded that of [1-(13)C]pyruvate conversion to [1-(13)C]lactate, potentially serving as a marker of HCC tumors.

BACKGROUND: Several meta-analyses indicate that there is an inverse genetic correlation between ethanol preference drinking and ethanol withdrawal severity, but limited work has characterized ethanol consumption in 1 genetic animal model, the Withdrawal Seizure-Prone (WSP) and-Resistant (WSR) mouse lines selected for severe or mild ethanol withdrawal, respectively. METHODS: We determined whether line differences existed in: (i) operant self-administration of ethanol during sucrose fading and under different schedules of reinforcement, followed by extinction and reinstatement of responding with conditioned cues and (ii) home cage drinking of sweetened ethanol and the development of an alcohol deprivation effect (ADE). RESULTS: Withdrawal Seizure-Prone-1 mice consumed more ethanol than WSR-1 mice under a fixed ratio (FR)-4 schedule as ethanol was faded into the sucrose solution, but this line difference dissipated as the sucrose was faded out to yield an unadulterated 10% v/v ethanol solution. In contrast, WSR-1 mice consumed more ethanol than WSP-1 mice when a schedule was imposed that procedurally separated appetitive and consummatory behaviors. After both lines achieved the extinction criterion, reinstatement was serially evaluated following oral ethanol priming, light cue presentation, and a combination of the 2 cues. The light cue produced maximal reinstatement of responding in WSP-1 mice, whereas the combined cue was required to produce maximal reinstatement of responding in WSR-1 mice. There was no line difference in the home cage consumption of a sweetened ethanol solution over a period of 1 month. Following a 2-week period of abstinence, neither line developed an ADE. CONCLUSIONS: Although some line differences in ethanol self-administration and reinstatement were identified between WSP-1 and WSR-1 mice, the absence of consistent divergence suggests that the genes underlying these behaviors do not reliably overlap with those that govern withdrawal severity.

Adult risk of alcohol dependence increases the younger one first engages in intoxicating consumption. Adolescent mice drink more ethanol than do adults on a g/kg basis, an increase sometimes persisting into adulthood, and this is genotype-dependent. Most studies have used 24-hr two-bottle preference, with choice between ethanol and water. We studied the developmental onset of binge drinking using limited access ethanol drinking in the dark (DID) in male and female mice. To establish age dependence in DID magnitude, we tested HS/Npt mice of 6 ages for DID for two weeks, and, when 9 weeks old, retested them for two weeks vs naïve adult controls. Age groups drank equivalently in their first week; thus, adolescent HS/Npt mice do not show greater DID than adults. Six week old mice drank more ethanol during their second week relative to their other weeks. Ethanol DID during early adolescence (4 weeks) led to increased drinking in adulthood, as did initial DID exposure at 8 weeks. High Drinking in the Dark-1 (HDID-1) mice (4, 6, 9 weeks old), selectively bred for high blood ethanol after DID, were tested for 9 weeks. Mice beginning at 4 weeks generally drank more ethanol than those of other age groups. Comparison at the same ages showed that 9 week olds initiated at 4 weeks drank more ethanol than did naïve 9 week olds, but all three groups of age-matched mice drank equivalent amounts once 10 weeks and older. The DID test is thus sensitive to developmental age. DID intakes by young adolescent HDID-1 mice were greater than by older mice, like studies with two-bottle preference. Early DID led to increased drinking as adults only in HS/Npt mice. HDID-1 mice provide a useful animal model for exploring whether DID and continuous access preference drinking have parallel consequences when initiated in adolescence.

BACKGROUND: Previous work from our laboratory demonstrated a role for the Drosophila Lim-only (dLmo) gene in regulating behavioral responses to cocaine. Herein, we examined whether dLmo influences the flies' sensitivity to ethanol's sedating effects. We also investigated whether 1 of the mammalian homologs of dLmo, Lmo3, is involved in behavioral responses to ethanol in mice. METHODS: To examine dLmo function in ethanol-induced sedation, mutant flies with reduced or increased dLmo expression were tested using the loss of righting (LOR) assay. To determine whether mouse Lmo3 regulates behavioral responses to ethanol, we generated transgenic mice expressing a short-hairpin RNA targeting Lmo3 for RNA interference-mediated knockdown by lentiviral infection of single cell embryos. Adult founder mice, expressing varying amounts of Lmo3 in the brain, were tested using ethanol loss-of-righting-reflex (LORR) and 2-bottle choice ethanol consumption assays. RESULTS: We found that in flies, reduced dLmo activity increased sensitivity to ethanol-induced sedation, whereas increased expression of dLmo led to increased resistance to ethanol-induced sedation. In mice, reduced levels of Lmo3 were correlated with increased sedation time in the LORR test and decreased ethanol consumption in the 2-bottle choice protocol. CONCLUSIONS: These data describe a novel and conserved role for Lmo genes in flies and mice in behavioral responses to ethanol. These studies also demonstrate the feasibility of rapidly translating findings from invertebrate systems to mammalian models of alcohol abuse by combining RNA interference in transgenic mice and behavioral testing.

GABA type A receptors (GABA(A)-Rs) are potential targets of ethanol. However, there are multiple subtypes of this receptor, and, thus far, individual subunits have not been definitively linked with specific ethanol behavioral actions. Interestingly, though, a chromosomal cluster of four GABA(A)-R subunit genes, including α2 (Gabra2), was associated with human alcoholism (Am J Hum Genet 74:705-714, 2004; Pharmacol Biochem Behav 90:95-104, 2008; J Psychiatr Res 42:184-191, 2008). The goal of our study was to determine the role of receptors containing this subunit in alcohol action. We designed an α2 subunit with serine 270 to histidine and leucine 277 to alanine mutations that was insensitive to potentiation by ethanol yet retained normal GABA sensitivity in a recombinant expression system. Knockin mice containing this mutant subunit were tested in a range of ethanol behavioral tests. These mutant mice did not develop the typical conditioned taste aversion in response to ethanol and showed complete loss of the motor stimulant effects of ethanol. Conversely, they also demonstrated changes in ethanol intake and preference in multiple tests. The knockin mice showed increased ethanol-induced hypnosis but no difference in anxiolytic effects or recovery from acute ethanol-induced motor incoordination. Overall, these studies demonstrate that the effects of ethanol at GABAergic synapses containing the α2 subunit are important for specific behavioral effects of ethanol that may be relevant to the genetic linkage of this subunit with human alcoholism.

Alcohol binge-drinking, especially among adolescents and young adults, is a serious public health concern. The present study examined ethanol binge-like drinking by peri-adolescent [postnatal days (PNDs 30-72)] and adult (PNDs 90-132) alcohol-preferring (P) rats with a drinking-in-the-dark-multiple-scheduled-access (DID-MSA) procedure used by our laboratory. Male and female P rats were provided concurrent access to 15% and 30% ethanol for three 1-h sessions across the dark cycle 5 days/week. For the 1st week, adolescent and adult female P rats consumed 3.4 and 1.6g/kg of ethanol, respectively, during the 1st hour of access, whereas for male rats the values were 3.5 and 1.1g/kg of ethanol, respectively. Adult intakes increased to \textasciitilde2.0 g/kg/h and adolescent intakes decreased to \textasciitilde2.5 g/kg/h across the 6 weeks of ethanol access. The daily ethanol intake of adult DID-MSA rats approximated or modestly exceeded that seen in continuous access (CA) rats or the selection criterion for P rats (≥5 g/kg/day). However, in general, the daily ethanol intake of DID-MSA peri-adolescent rats significantly exceeded that of their CA counterparts. BELs were assessed at 15-min intervals across the 3rd hour of access during the 4th week. Ethanol intake was 1.7 g/kg vs. 2.7 g/kg and BELs were 57 mg% vs. 100mg% at 15- and 60-min, respectively. Intoxication induced by DID-MSA in female P rats was assessed during the 1st vs. 4th week of ethanol access. Level of impairment did not differ between the 2 weeks (106 vs. 97 s latency to fall, 120 s criterion) and was significant (vs. naïve controls) only during the 4th week. Overall, these findings support the use of the DID-MSA procedure in rats, and underscore the presence of age- and sex-dependent effects mediating ethanol binge-like drinking in P rats.

BACKGROUND: Alcohol addiction develops through a series of stages, and mechanistic studies are needed to understand the transition from initial drug use to sustained controlled alcohol consumption followed by abuse and physical dependence. The focus of this study was to examine the effects of voluntary alcohol consumption on brain gene expression profiles using a mouse model of binge drinking. The main goal was to identify alcohol-responsive genes and functional categories after a single episode of drinking to intoxication. METHODS: We used a modification of a "Drinking In the Dark" (DID) procedure (Rhodes et al., 2005) that allows mice to experience physiologically relevant amounts of alcohol in a non-stressful environment and also allows for detection of alcohol-sensitive molecular changes in a dose-dependent manner. C57BL/6J male mice were exposed to either 20% ethanol solution or water (single bottle) starting 3 hours after lights off for 4 hours and brains were harvested immediately after the drinking session. cDNA microarrays were used to assess the effects of voluntary drinking on global gene expression in 6 brain regions. We employed three statistical approaches to analyze microarray data. RESULTS: A commonly used approach that applies a strict statistical threshold identified the eight top statistically significant genes whose expression was significantly correlated with blood ethanol concentration (BEC) in one of the brain regions. We then used a systems network approach to examine brain region-specific transcriptomes and identify modules of co-expressed (correlated) genes. In each brain region, we identified alcohol-responsive modules, i.e., modules significantly enriched for genes whose expression was correlated with BEC. A functional over-representation analysis was then applied to examine the organizing principles of alcohol-responsive modules. Genes were clustered into modules according to their roles in different physiological processes, functional groups, and cell types, including blood circulation, signal transduction, cell-cell communication, and striatal neurons. Finally, a meta-analysis across all brain regions suggested a global role of increasing alcohol dose in coordination of brain blood circulation and reaction of astrocytes. CONCLUSIONS: This study showed that acute drinking resulted in small but consistent changes in brain gene expression which occurred in a dose-dependent manner. We identified both general and region-specific changes, some of which represent adaptive changes in response to increasing alcohol dose, which may play a role in alcohol-related behaviours, such as tolerance and consumption. Our systems approach allowed us to estimate the functional values of individual genes in the context of their genetic networks and formulate new refined hypotheses. An integrative analysis including other alcohol studies suggested several top candidates for functional validation, including Mt2, Gstm1, Scn4b, Prkcz, and Park7.