Ethanol and amino acids in the central nervous system: assessment of the pharmacological actions of acamprosate

Acute taurine reduced alcohol intake and preference in alcohol-experienced, but not in alcohol-näive rats by central mechanisms

Taurine is a non-essential β sulfonated amino acid involved in a plethora of biological functions in the mammalian central nervous system. Taurine is easily accessible in energy drinks for human consumption. Previous preclinical and clinical reports suggest that acute systemic administration of taurine could inhibit some of the behavioral and metabolic effects of alcohol use disorder. Overall, both in rodent and human studies, acute taurine administration reduced voluntary alcohol intake. This study aimed to assess the pharmacological effects of taurine (intracerebroventricular; i.c.v.) on ethanol intake/preference of rats either control (i.e., alcohol naïve) or forced ethanol intake (since juvenile age with a chronic intermittent access model). In addition, to explore anxiety-like behavior (through defensive burying behavior test) as pharmacological control of taurine. We found that acute (i.c.v.) taurine reduced alcohol consumption, i.e., taurine significantly decreased both alcohol intake and preference in adult male Wistar rats. Moreover, taurine elicits an anxiolytic-like effect in all administered groups independently of previous alcohol exposure.

Current treatments of alcohol use disorder

Emerging treatments for alcohol dependence reveal an intricate interplay of neurobiological, psychological, and circumstantial factors that contribute to Alcohol Use Disorder (AUD). The approved strategies balancing these factors involve extensive manipulations of neurotransmitter systems such as GABA, Glutamate, Dopamine, Serotonin, and Acetylcholine. Innovative developments are engaging mechanisms such as GABA reuptake inhibition and allosteric modulation. Closer scrutiny is placed on the role of Glutamate in chronic alcohol consumption, with treatments like NMDA receptor antagonists and antiglutamatergic medications showing significant promise. Complementing these neurobiological approaches is the progressive shift towards Personalized Medicine. This strategy emphasizes unique genetic, epigenetic and physiological factors, employing pharmacogenomic principles to optimize treatment response. Concurrently, psychological therapies have become an integral part of the treatment landscape, tackling the cognitive-behavioral dimension of addiction. In instances of AUD comorbidity with other psychiatric disorders, Personalized Medicine becomes pivotal, ensuring treatment and prognosis are closely defined by individual characteristics, as exemplified by Lesch Typology models. Given the high global prevalence and wide distribution of AUD, a persistent necessity exists for development and improvement of treatments. Current research efforts are steadily paving paths towards more sophisticated, effective typology-based treatments: a testament to the recognized imperative for enhanced treatment strategies. The potential encapsulated within the ongoing research suggests a promising future where the clinical relevance of current strategies is not just maintained but significantly improved to effectively counter alcohol dependence.

Acamprosate reduces ethanol intake in the rat by a combined action of different drug components

Alcohol misuse accounts for a sizeable proportion of the global burden of disease, and Campral® (acamprosate; calcium-bis-(N-acetylhomotaurinate)) is widely used as relapse prevention therapy. The mechanism underlying its effect has in some studies been attributed to the calcium moiety and not to the N-acetylhomotaurine part of the compound. We recently suggested that the dopamine elevating effect of acamprosate is mediated both by N-acetylhomotaurine and calcium in a glycine receptor dependent manner. Here we aimed to explore, by means of in vivo microdialysis, if our previous study using local administration was functionally relevant and if systemic administration of the sodium salt of N-acetylhomotaurine (sodium acamprosate; 200 mg/kg, i.p.) enhanced the effects of calcium chloride (CaCl2; 73.5 mg/kg, i.p.) on nucleus accumbens (nAc) dopamine and/or taurine levels in male Wistar rats. In addition, we investigated the impact of regular acamprosate and the combination of CaCl2 and N-acetylhomotaurine on the alcohol deprivation effect (ADE). Finally, we assessed if N-acetylhomotaurine potentiates the ethanol-intake reducing effect of CaCl2 in a two-bottle choice voluntary ethanol consumption model followed by an ADE paradigm. Systemic administration of regular acamprosate, sodium acamprosate and CaCl2 all trended to increase nAc dopamine whereas the combination of CaCl2 and sodium acamprosate produced a significant increase. Sodium acamprosate elevated extracellular taurine levels without additional effects of CaCl2. Ethanol intake was significantly reduced by systemic administration of CaCl2 without additional effects of the combination of CaCl2 and sodium acamprosate. Both acamprosate and CaCl2 combined with sodium acamprosate blocked the ADE following acute treatment. The data presented suggest that CaCl2 and N-acetylhomotaurine act in concert on a neurochemical level, but calcium appears to have the predominant effect on ethanol intake.

Alcohol Consumption and Mild Cognitive Impairment: A Mendelian Randomization Study from Rural China

Alcohol consumption has been associated with the risk of mild cognitive impairment (MCI) in observational studies. The result is inconsistent and whether the association is causal remains unknown. To examine the causal effect of alcohol consumption on MCI in rural China, this study used a cross-sectional dataset that included 1966 observations collected in rural China, of which 235 observations’ genotyping were collected. All participants accepted the MCI evaluation using Mini-Cog and were asked about the participants’ alcohol consumption behavior. The causal effect of alcohol consumption on MCI was investigated by Mendelian randomization (MR) of genetic variation in the aldehyde dehydrogenase 2 (ALDH2 rs671) gene. The risk of MCI in Chinese rural areas was 43%. Alcohol consumption was causally associated with a higher risk of MCI under MR design. Parameter estimates of drinking or not (b = 0.271, p = 0.007, 95% CI = 0.073 to 0.469), drinking frequency during the past 30 days (b = 0.016, p = 0.003, 95% CI = 0.005 to 0.027), and the weekly ethanol consumption (b = 0.132, p = 0.004, 95% CI = 0.042 to 0.223) were all positive and statistically significant at the 5% level. In conclusion, there was a high risk of MCI in rural China, and alcohol consumption was causally associated with a higher risk of MCI.

The Persistent Challenge of Developing Addiction Pharmacotherapies

There are currently effective Food and Drug Administration (FDA)-approved therapies for alcohol, nicotine, and opioid use disorders. This article will review the development of eight compounds used in the treatment of drug addiction with an emphasis on pharmacological mechanisms and the utility of preclinical animal models of addiction in therapeutic development. In contrast to these successes, animal research has identified a number of promising medications for the treatment of psychostimulant use disorder, none of which have proven to be clinically effective. A specific example of an apparently promising pharmacotherapeutic for cocaine that failed clinically will be examined to determine whether this truly represents a challenge to the predictive validity of current models of cocaine addiction. In addition, the development of promising cocaine use disorder therapeutics derived from animal research will be reviewed, with some discussion regarding how preclinical studies might be modified to better inform clinical outcomes.

Taurine enhances voluntary alcohol intake and promotes anxiolytic-like behaviors in rats

Taurine is an amino acid usually added to energy drinks. In rodents, acute taurine administration decreases voluntary alcohol intake, and subchronic administration restores different behavioral features impaired by alcohol withdrawal. In the present study, we evaluated the effects of chronic taurine treatment on voluntary alcohol consumption and changes in behavioral parameters in rats. Adult male Wistar rats were divided into two groups and were allowed to choose from two bottles containing 20% alcohol or 0.08% saccharin (vehicle solution), or two bottles containing vehicle, 24 h per day, for 5 weeks. After 3 weeks, rats received 100 mg/kg taurine (TAU) or saline (SAL) intraperitoneally once a day for 2 weeks, and daily alcohol consumption was monitored. On days 22 and 33, rats were tested in the open-field, and on day 34, they were exposed to the light/dark task (LDT). Our results show for the first time that chronic taurine treatment enhanced voluntary alcohol intake and preference in rats, and that these changes were accompanied by an anxiolytic-like phenotype in alcohol-treated rats, possibly due to its synergistic effect with alcohol on the dopaminergic and GABAergic systems.

Ethanol-induced changes in synaptic amino acid neurotransmitter levels in the nucleus accumbens of differentially sensitized mice

RATIONALE

Ethanol-induced behavioural sensitization (EBS) does not occur uniformly in mice exposed to the sensitization paradigm. This suggests innate differential responses to ethanol (EtOH) in the reward circuitry of individual animals.

OBJECTIVES

To better characterize the adaptive differences between low-sensitized (LS) and high-sensitized (HS) mice, we examined excitatory amino acid (EAA) and inhibitory amino acid (IAA) neurotransmitter levels in the nucleus accumbens (NAc) during EBS expression.

METHODS

Male DBA/2J mice received five ethanol (EtOH) (2.2 g/kg) or saline injections, and locomotor activity (LMA) was assessed during EBS induction. EtOH mice were classified as LS or HS on the basis of final LMA scores. Following an EtOH challenge (1.8 g/kg) 2 weeks later, LMA was re-evaluated and in vivo microdialysis samples were collected from the NAc.

RESULTS

Most differences in amino acid levels were observed within the first 20 min after EtOH challenge. LS mice exhibited similar glutamate levels compared with acutely treated (previously EtOH naïve) mice, and generally increased levels of the IAAs GABA, glycine, and taurine. By contrast, HS mice exhibited increased glutamate and attenuated levels of GABA, glycine, and taurine.

CONCLUSION

These data suggest that the profile of amino acid neurotransmitters in the NAc of LS and HS mice significantly differs. Elucidating these adaptive differences contributes to our understanding of factors that confer susceptibility/resilience to alcohol use disorder.

Alcohol dependence treating agent, acamprosate, prevents traumatic brain injury-induced neuron death through vesicular zinc depletion

Acamprosate, also known as N-acetyl homotaurine, is an N-methyl-d-aspartate receptor antagonist that is used for treating alcohol dependence. Although the exact mechanism of acamprosate has not been clearly established, it appears to work by promoting a balance between the excitatory and inhibitory neurotransmitters, glutamate, and gamma-aminobutyric acid, respectively. Several studies have demonstrated that acamprosate provides neuroprotection against ischemia-induced brain injury. However, no studies have been performed evaluating the effect of acamprosate on traumatic brain injury (TBI). In the present study, we sought to evaluate the therapeutic potential of acamprosate to protect against neuronal death following TBI. Rats were given oral acamprosate (200 mg/kg/d for 2weeks) and then subjected to a controlled cortical impact injury localized over the parietal cortex. Histologic analysis was performed at 3hours, 24hours, and 7days after TBI. We found that acamprosate treatment reduced the concentration of vesicular glutamate and zinc in the hippocampus. Consequently, this reduced vesicular glutamate and zinc level resulted in a reduction of reactive oxygen species production after TBI. When evaluated 24hours after TBI, acamprosate administration reduced the number of degenerating neurons, zinc accumulation, blood-brain barrier disruption, neutrophil infiltration, and dendritic loss. Acamprosate also reduced glial activation and neuronal loss at 7days after TBI. In addition, acamprosate rescued TBI-induced neurologic and cognitive dysfunction. The present study demonstrates that acamprosate attenuates TBI-induced brain damage by depletion of vesicular glutamate and zinc levels. Therefore, this study suggests that acamprosate may have high therapeutic potential for prevention of TBI-induced neuronal death.

Acamprosate's ethanol intake-reducing effect is associated with its ability to increase dopamine

Previous studies indicate that the anti-craving substance acamprosate modulates nucleus accumbens (nAc) dopamine levels via a dopamine-controlling nAc-VTA-nAc neurocircuitry. It was demonstrated that glycine receptors in the nAc are involved both in the dopamine-elevating effect and the ethanol intake-reducing effect of the drug. Here we wanted to explore the interaction of ethanol and acamprosate on nAc dopamine and investigate whether dopaminergic transmission may be related to the ethanol intake-reducing effects. In three separate studies we investigated nAc extracellular dopamine levels by means of in vivo microdialysis after administration of acamprosate and ethanol in 1) naïve rats, 2) rats pre-treated with acamprosate for two days or 3) ethanol medium- and high-preferring rats receiving ten days of acamprosate pre-treatment. In the first two studies, acamprosate elevated dopamine and simultaneously prevented ethanol from further increasing dopamine output. In the third study, long-term acamprosate pre-treatment produced a loss of the ethanol intake-reducing as well as the dopamine-elevating effects of acamprosate, and the dopamine elevating property of ethanol was restored. We suggest that acamprosate may partly substitute for the dopamine-elevating effect of ethanol but once tolerance develops to this effect, the ability to decrease ethanol intake is lost.

Generation of silent synapses in dentate gyrus correlates with development of alcohol addiction

The brain circuits and synaptic processes that underlie alcohol addiction are currently the subject of intensive research. Here we focus on hippocampal circuitry and show that chemogenetic inhibition of dentate gyrus (DG) during presentation of alcohol-associated cues has long-lasting effects on mice behavior. DG inhibition enhances alcohol seeking and drinking, suggesting that DG regulates addiction-related behaviors. To test this hypothesis, we perform whole-cell patch-clamp recordings from the granule cells of DG and look for electrophysiological correlates of alcohol addiction. We observe that presentation of alcohol-associated cue light that induces relapse to alcohol-seeking results in generation of silent synapses, that lack functional AMPA receptors. Furthermore, using human criteria of addiction, we differentiate mice controlling their alcohol consumption from those that undergo transition to addiction to discover that the levels of silent synapses induced by alcohol cues are specifically increased in the addicted mice. As the total level of dendritic spines that harbor synapses is constant at this time point, our data indicate that synapses of perforant path to DG are weakened during cue relapse. Finally we demonstrate that, acamprosate, a drug that limits alcohol drinking and seeking in addicts, prevents generation of silent synapses in DG upon presentation of alcohol-associated cues. Altogether, our data suggest that weakening of DG synapses upon cue relapse contributes to persistent alcohol addiction-related behaviors.

Acute effect of Ethanol and Taurine on frontal cortex absolute beta power before and after exercise

Ethanol (ET) is a substance that modulates the Central Nervous System (CNS). Frequently, ET intake occurs combined with energy drinks, which contain taurine (TA), an important amino acid found in the body (i.e brain and muscles). Although TA administration has been used in the improvement of physical performance, the impact of TA, ET and exercise remains unknown. This study aimed to analyze the acute effect of 6g of Taurine (TA), 0.6 mL∙kg^-1 of Ethanol (ET), and Taurine combined with Ethanol (TA+ET) ingestion on the electrocortical activity before and after a moderate intensity exercise in 9 subjects, 5 women (counterbalanced experimental design). In each of the 4 treatments (Placebo—PL, TA, ET and TA+ET), electroencephalography (EEG) tests were conducted in order to analyze changes in absolute beta power (ABP) in the frontal lobe in 3 moments: baseline (before ingestion), peak (before exercise) and post-exercise. In the PL treatment, the frontal areas showed decrease in ABP after exercise. However, in the ET+TA treatment, ABP values were greater after exercise, except for Fp1. The ET treatment had no effect on the Superior Frontal Gyrus area (F3, Fz and F4) and ABP decreased after exercise in Fp1 and Fp2. In the TA treatment, ABP increased after exercise, while it decreased at the peak moment in most of the frontal regions, except for Fp1, F3 and Fz. We concluded that after a moderate intensity exercise, a decrease in cortical activity occurs in placebo treatment. Moreover, we found a inhibitory effect of TA on cortical activity before exercise and a increased in cortical activity after exercise. A small ET dose is not enough to alter ABP in all regions of the frontal cortex and, in combination with TA, it showed an increase in the frontal cortex activity at the post-exercise moment.

Purinergic Signaling in Neuron-Astrocyte Interactions, Circadian Rhythms, and Alcohol Use Disorder

Alcohol use disorder (AUD) is a debilitating condition marked by cyclic patterns of craving, use, and withdrawal. These pathological behaviors are mediated by multiple neurotransmitter systems utilizing glutamate, GABA, dopamine, ATP, and adenosine. In particular, purines such as ATP and adenosine have been demonstrated to alter the phase and function of the circadian clock and are reciprocally regulated by the clock itself. Importantly, chronic ethanol intake has been demonstrated to disrupt the molecular circadian clock and is associated with altered circadian patterns of activity and sleep. Moreover, ethanol has been demonstrated to disrupt purinergic signaling, while dysfunction of the purinergic system has been implicated in conditions of drug abuse such as AUD. In this review, we summarize our current knowledge regarding circadian disruption by ethanol, focusing on the reciprocal relationship that exists between oscillatory neurotransmission and the molecular circadian clock. In particular, we offer detailed explanations and hypotheses regarding the concerted regulation of purinergic signaling and circadian oscillations by neurons and astrocytes, and review the diverse mechanisms by which purinergic dysfuction may contribute to circadian disruption or alcohol abuse. Finally, we describe the mechanisms by which ethanol may disrupt or hijack endogenous circadian rhythms to induce the maladaptive behavioral patterns associated with AUD.

Are Alcohol Anti-relapsing and Alcohol Withdrawal Drugs Useful in Cannabinoid Users?

Cannabinoids are still classified as illegal psychoactive drugs despite their broad and increasingly acknowledged therapeutic potential. These substances are most famous for their wide recreational use, particularly among young adults to either alter the state of consciousness, intensify pleasure induced by other psychoactive substances or as an alternative to the previously abused drugs. It is important to emphasize that cannabinoids are often taken together with a variety of medications intended for the treatment of alcohol use disorder (AUD) or alcohol withdrawal syndrome (AWS). These medications include disulfiram, acamprosate, and naltrexone. In this paper, we summarize recent advances in the knowledge of possible beneficial effects and interactions between cannabinoids and drugs commonly used for treatment of AUD and AWS either comorbid or existing as a separate disorder.

Noni (Morinda citrifolia Linn.) fruit juice attenuates the rewarding effect of ethanol in conditioned place preference in mice

Morinda citrifolia L. commonly known as noni or Indian mulberry belongs to the family Rubiaceae. Noni fruit juice has recently become a very popular remedy for the treatment of several diseases, including psychiatric disorders. This study aimed to investigate the anticraving effect of Tahitian Noni® Juice (TNJ) against ethanol seeking behavior in ICR male mice using the conditioned place preference (CPP) test. The CPP procedure consisted of four phases: preconditioning, conditioning, extinction, and reinstatement. During conditioning, intraperitoneal (i.p.) injections of ethanol (2 g/kg body weight (bw)) and normal saline (10 ml/kg bw) were given on alternate days for 12 days. Then, the animals were subjected to extinction trials for the next 12 days to weaken CPP. Finally, CPP was reinstated in the extinguished animals by a single low-dose priming injection of ethanol (0.4 g/kg bw, i.p.). The effect of TNJ (as a source of drinking water) on different phases of ethanol CPP in mice was studied. TNJ-treated mice showed a significant reduction in ethanol seeking behavior in the CPP test. The reference drug, acamprosate (ACAM) also showed a similar effect in the CPP test. The outcome of this study suggests that TNJ is effective in attenuating ethanol craving in mice and could be utilized for the treatment of alcohol dependence. Further clinical studies in this direction are warranted to support the present preclinical findings.

The indirect NMDAR antagonist acamprosate induces postischemic neurologic recovery associated with sustained neuroprotection and neuroregeneration

Cerebral ischemia stimulates N-methyl-d-aspartate receptors (NMDARs) resulting in increased calcium concentration and excitotoxicity. Yet, deactivation of NMDAR failed in clinical studies due to poor preclinical study designs or toxicity of NMDAR antagonists. Acamprosate is an indirect NMDAR antagonist used for patients with chronic alcohol dependence. We herein analyzed the therapeutic potential of acamprosate on brain injury, neurologic recovery and their underlying mechanisms. Mice were exposed to cerebral ischemia, treated with intraperitoneal injections of acamprosate or saline (controls), and allowed to survive until 3 months. Acamprosate yielded sustained neuroprotection and increased neurologic recovery when given no later than 12 hours after stroke. The latter was associated with increased postischemic angioneurogenesis, albeit acamprosate did not stimulate angioneurogenesis itself. Rather, increased angioneurogenesis was due to inhibition of calpain-mediated pro-injurious signaling cascades. As such, acamprosate-mediated reduction of calpain activity resulted in decreased degradation of p35, increased abundance of the pro-survival factor STAT6, and reduced N-terminal-Jun-kinase activation. Inhibition of calpain was associated with enhanced stability of the blood-brain barrier, reduction of oxidative stress and cerebral leukocyte infiltration. Taken into account its excellent tolerability, its sustained effects on neurologic recovery, brain tissue survival, and neural remodeling, acamprosate is an intriguing candidate for adjuvant future stroke treatment.

Elevated baseline serum glutamate as a pharmacometabolomic biomarker for acamprosate treatment outcome in alcohol-dependent subjects

Acamprosate has been widely used since the Food and Drug Administration approved the medication for treatment of alcohol use disorders (AUDs) in 2004. Although the detailed molecular mechanism of acamprosate remains unclear, it has been largely known that acamprosate inhibits glutamate action in the brain. However, AUD is a complex and heterogeneous disorder. Thus, biomarkers are required to prescribe this medication to patients who will have the highest likelihood of responding positively. To identify pharmacometabolomic biomarkers of acamprosate response, we utilized serum samples from 120 alcohol-dependent subjects, including 71 responders (maintained continuous abstinence) and 49 non-responders (any alcohol use) during 12 weeks of acamprosate treatment. Notably, baseline serum glutamate levels were significantly higher in responders compared with non-responders. Importantly, serum glutamate levels of responders are normalized after acamprosate treatment, whereas there was no significant glutamate change in non-responders. Subsequent functional studies in animal models revealed that, in the absence of alcohol, acamprosate activates glutamine synthetase, which synthesizes glutamine from glutamate and ammonia. These results suggest that acamprosate reduces serum glutamate levels for those who have elevated baseline serum glutamate levels among responders. Taken together, our findings demonstrate that elevated baseline serum glutamate levels are a potential biomarker associated with positive acamprosate response, which is an important step towards development of a personalized approach to treatment for AUD.

Targeting glutamate uptake to treat alcohol use disorders

Alcoholism is a serious public health concern that is characterized by the development of tolerance to alcohol's effects, increased consumption, loss of control over drinking and the development of physical dependence. This cycle is often times punctuated by periods of abstinence, craving and relapse. The development of tolerance and the expression of withdrawal effects, which manifest as dependence, have been to a great extent attributed to neuroadaptations within the mesocorticolimbic and extended amygdala systems. Alcohol affects various neurotransmitter systems in the brain including the adrenergic, cholinergic, dopaminergic, GABAergic, glutamatergic, peptidergic, and serotonergic systems. Due to the myriad of neurotransmitter and neuromodulator systems affected by alcohol, the efficacies of current pharmacotherapies targeting alcohol dependence are limited. Importantly, research findings of changes in glutamatergic neurotransmission induced by alcohol self- or experimenter-administration have resulted in a focus on therapies targeting glutamatergic receptors and normalization of glutamatergic neurotransmission. Glutamatergic receptors implicated in the effects of ethanol include the ionotropic glutamate receptors (AMPA, Kainate, and NMDA) and some metabotropic glutamate receptors. Regarding glutamatergic homeostasis, ceftriaxone, MS-153, and GPI-1046, which upregulate glutamate transporter 1 (GLT1) expression in mesocorticolimbic brain regions, reduce alcohol intake in genetic animal models of alcoholism. Given the hyperglutamatergic/hyperexcitable state of the central nervous system induced by chronic alcohol abuse and withdrawal, the evidence thus far indicates that a restoration of glutamatergic concentrations and activity within the mesocorticolimbic system and extended amygdala as well as multiple memory systems holds great promise for the treatment of alcohol dependence.

The development of acamprosate as a treatment against alcohol relapse

INTRODUCTION

Globally, alcohol abuse and dependence are significant contributors to chronic disease and injury and are responsible for nearly 4% of all deaths annually. Acamprosate (Campral), one of only three pharmacological treatments approved for the treatment of alcohol dependence, has shown mixed efficacy in clinical trials in maintaining abstinence of detoxified alcoholics since studies began in the 1980s. Yielding inconsistent results, these studies have prompted skepticism.

AREAS COVERED

Herein, the authors review the preclinical studies which have assessed the efficacy of acamprosate in various animal models of alcohol dependence and discuss the disparate findings from the major clinical trials. Moreover, the authors discuss the major limitations of these preclinical and clinical studies and offer explanations for the often-contradictory findings. The article also looks at the importance of the calcium moiety that accompanies the salt form of acamprosate and its relevance to its activity.

EXPERT OPINION

The recent discovery that large doses of calcium largely duplicate the effects of acamprosate in animal models has introduced a serious challenge to the widely held functional association between this drug and the glutamate neurotransmission system. Future research on acamprosate or newer pharmacotherapeutics should consider assessing plasma and/or brain levels of calcium as a correlate or mediating factor in anti-relapse efficacy. Further, preclinical research on acamprosate has thus far lacked animal models of chemical dependence on alcohol, and the testing of rodents with histories of alcohol intoxication and withdrawal is suggested.

The clinical pharmacology of acamprosate

Acamprosate is one of the few medications licensed for prevention of relapse in alcohol dependence, and over time it has proved to be significantly, if moderately, effective, safe and tolerable. Its use is now being extended into other addictions and neurodevelopmental disorders. The mechanism of action of acamprosate has been less clear, but in the decade or more that has elapsed since its licensing, a body of translational evidence has accumulated, in which preclinical findings are replicated in clinical populations. Acamprosate modulates N-methyl-d-aspartic acid receptor transmission and may have indirect effects on γ-aminobutyric acid type A receptor transmission. It is known to decrease brain glutamate and increase β-endorphins in rodents and man. Acamprosate diminishes reinstatement in ethanolized rodents and promotes abstinence in humans. Although acamprosate has been called an anticraving drug, its subjective effects are subtle and relate to diminished arousal, anxiety and insomnia, which parallel preclinical findings of decreased withdrawal symptoms in animals treated with acamprosate. Further understanding of the pharmacology of acamprosate will allow appropriate targeting of therapy in individuals with alcohol dependence and extension of its use to other addictions.

Rational development of addiction pharmacotherapies: successes, failures, and prospects

There are currently effective, U.S. Food and Drug Administration (FDA)-approved therapies for alcohol, nicotine, and opioid addiction. In some cases these therapeutics were rationally designed and tested using a combination of various animal models of addiction. In many cases, however, effective drug therapies for addiction were derived from the testing of compounds developed for other CNS disorders (e.g., analgesics and antidepressants), which were tested clinically in the absence of prior animal research using addiction models. This article will review the development of eight compounds that are currently most effective in the treatment of alcohol, opioid, and nicotine addiction with an emphasis on pharmacological mechanisms as well as the utility of animal models of addiction in the development of these therapeutics. In contrast to these successes, animal research has identified a number of promising medications for the treatment of psychostimulant addiction, none of which have proven to be effective clinically. This raises questions about the validity of current animal models of psychostimulant addiction. A specific example of an apparently promising pharmacotherapeutic for cocaine addiction (the D1 dopamine receptor antagonist ecopipam) that failed clinically will be examined to determine if this truly represents a challenge to the predictive validity of current models of cocaine addiction. In addition, the development of promising cocaine addiction therapeutics derived from animal research will be reviewed.

Antidepressant effect of aminophylline after ethanol exposure

This work investigated the association of acute ethanol and aminophylline administration on behavioral models of depression and prefrontal monoamine levels (i.e. norepinephrine and dopamine) in mice. The animals received a single dose of ethanol (2 g/kg) or aminophylline (5 or 10 mg/kg) alone or in association. Thirty minutes after the last drug administration, the animals were assessed in behavioral models by the forced swimming and tail suspension tests. After these tests, the animals were sacrificed and the prefrontal cortices dissected to measure monoamine content. Results showed that ethanol presented depression-like activity in the forced swimming and tail suspension tests. These effects were reversed by the association with aminophylline in all tests. Norepinephrine and dopamine levels decreased, while an increase in the dopamine metabolite, (4-hydroxy-3-methoxyphenyl)acetic acid (DOPAC), after ethanol administration was observed. On the contrary, the association of ethanol and aminophylline increased the norepinephrine and dopamine content, while it decreased DOPAC when compared to the ethanol group, confirming the alterations observed in the behavioral tests. These data reinforce the involvement of the adenosinergic system on ethanol effects, highlighting the importance of the norepinephrine and dopamine pathways in the prefrontal cortex to the effects of ethanol.

Differential effects of baclofen and oxytocin on the increased ethanol consumption following chronic psychosocial stress in mice

Chronic stress is known to enhance the susceptibility for addiction disorders including alcoholism. While these findings have been recapitulated in animal models, the majority of these studies have utilized non-social rather than social stress paradigms; the latter of which are believed to be more relevant to the human situation. Therefore, the major aim of this study was to investigate, if 14 days of chronic subordinate colony housing (CSC), a pre-clinically validated psychosocial stress paradigm relevant for human psychiatric and somatic disorders, enhances ethanol (EtOH) consumption in male mice. To assess this, we employed the well-established two-bottle free-choice paradigm where mice were given access to water and 2, 4, 6 and 8% EtOH solutions (with the concentrations increasing each fourth day) following termination of the stress procedure. After 14 days of CSC, stressed mice consumed significantly more EtOH at all concentrations tested and displayed increased EtOH preference at concentrations of 6 and 8%. This effect was not due to an altered taste preference in CSC mice as assessed by saccharine- and quinine-preference tests, but was accompanied by increased anxiety-related behavior. Systemic administration of baclofen (2.5 mg/kg) or oxytocin (OXT; 10 mg/kg) reduced the EtOH intake in single housed control (baclofen, OXT) and CSC (baclofen) mice, whereas intracerebroventricular OXT (0.5 μg/2 μl) was ineffective in both groups. Taken together, these results suggest that (i) chronic psychosocial stress enhances EtOH consumption, and (ii) baclofen and OXT differentially affect EtOH intake in mice.

Ethanol withdrawal-induced brain metabolites and the pharmacological effects of acamprosate in mice lacking ENT1

Acamprosate is clinically used to treat alcohol-dependent patients. While the molecular and pharmacological mechanisms of acamprosate remain unclear, it has been shown to regulate γ-aminobutyric acid (GABA) or glutamate levels in the cortex and striatum. To investigate the effect of acamprosate on brain metabolites in the medial prefrontal cortex (mPFC) and nucleus accumbens (NAc), we employed in vivo 16.4 T proton magnetic resonance spectroscopy. We utilized type 1 equilibrative nucleoside transporter (ENT1) null mice since acamprosate attenuates ethanol drinking in these mice. Our findings demonstrated that ethanol withdrawal reduced GABA levels and increased phosphorylated choline compounds in the mPFC of both wild-type and ENT1 null mice. Notably, acamprosate normalized these withdrawal-induced changes only in ENT1 null mice. In the NAc, ethanol withdrawal increased glutamate and glutamine (Glx) levels only in wild-type mice. Interestingly, acamprosate reduced Glx levels in the NAc compared to the withdrawal state in both genotypes. These results provide a molecular basis for the pharmacological effect of acamprosate in the cortical-striatal circuit.

Event-Related Oscillations in Alcoholism Research: A Review

Alcohol dependence is characterized as a multi-factorial disorder caused by a complex interaction between genetic and environmental liabilities across development. A variety of neurocognitive deficits/dysfunctions involving impairments in different brain regions and/or neural circuitries have been associated with chronic alcoholism, as well as with a predisposition to develop alcoholism. Several neurobiological and neurobehavioral approaches and methods of analyses have been used to understand the nature of these neurocognitive impairments/deficits in alcoholism. In the present review, we have examined relatively novel methods of analyses of the brain signals that are collectively referred to as event-related oscillations (EROs) and show promise to further our understanding of human brain dynamics while performing various tasks. These new measures of dynamic brain processes have exquisite temporal resolution and allow the study of neural networks underlying responses to sensory and cognitive events, thus providing a closer link to the physiology underlying them. Here, we have reviewed EROs in the study of alcoholism, their usefulness in understanding dynamical brain functions/dysfunctions associated with alcoholism as well as their utility as effective endophenotypes to identify and understand genes associated with both brain oscillations and alcoholism.

Acamprosate modulates experimental autoimmune encephalomyelitis

OBJECTIVE

This pilot study aimed to determine the efficacy of acamprosate (N-acetyl homotaurine) in reducing the pathological features of experimental autoimmune encephalomyelitis (EAE) which is an animal model for multiple sclerosis (MS).

BACKGROUND

The amino acid taurine has multiple biological activities including immunomodulation and neuromodulation. The synthetic acetylated taurine derivative, acamprosate, which crosses the blood-brain barrier more readily compared to taurine, is currently being used for the prevention of alcohol withdrawal symptoms associated with enhanced glutamatergic receptor function and GABA receptor hypofunction.

METHODS

EAE was induced in C57BL/6 female mice with myelin oligodendrocyte glyocoprotein, amino acid 35-55. Mice were treated with 20, 100 and 500 mg/kg acamprosate for 21 days.

RESULTS

Neurological scores at disease peak were reduced by 21, 64 and 9% in the 20, 100 and 500 mg/kg groups, respectively. Neurological improvement in the 100 mg/kg group correlated with a reduction in numbers of inflammatory lesions and the extent of CNS demyelination. Blood TNF-α levels were significantly reduced in the 500 mg/kg group.

DISCUSSION

Acamprosate and other taurine analogs have a potential for future MS therapy.

Behavioral deficits and cellular damage following developmental ethanol exposure in rats are attenuated by CP-101,606, an NMDAR antagonist with unique NR2B specificity

NMDAR-mediated excitotoxicity has been implicated in some of the impairments following fetal ethanol exposure. Previous studies suggest that both neuronal cell death and some of the behavioral deficits can be reduced by NMDAR antagonism during withdrawal, including antagonism of a subpopulation of receptors containing NR2B subunits. To further investigate NR2B involvement, we selected a compound, CP-101,606 (CP) which binds selectively to NR2B/2B stoichiometries, for both in vitro and in vivo analyses. For the in vitro study, hippocampal explants were exposed to ethanol for 10 days and then 24 h following removal of ethanol, cellular damage was quantified via propidium iodide fluorescence. In vitro ethanol withdrawal-associated neurotoxicity was prevented by CP (10 and 25 nM). In vivo ethanol exposure was administered on PNDs 1-7 with CP administered 21 h following cessation. Activity (PNDs 20-21), motor skills (PNDs 31-33), and maze navigation (PNDs 43-44) were all susceptible to ethanol insult; treatment with CP (15 mg/kg) rescued these deficits. Our findings show that CP-101,606, a drug that blocks the NR2B/2B receptor, can reduce some of the damaging effects of "3rd trimester" alcohol exposure in our rodent model. Further work is clearly warranted on the neuroprotective potential of this drug in the developing brain.

A double-blind, placebo-controlled pilot trial of acamprosate for the treatment of cocaine dependence

BACKGROUND

Acamprosate is a medication shown to be effective for the treatment of alcohol dependence. Although the exact mechanism of action of acamprosate is unknown, evidence suggests that it decreases excitatory amino acid activity by post-synaptic inhibition of the NMDA subtype of glutamate receptors. It is possible that the activity of acamprosate via modulating glutamatergic activity could also reduce craving for cocaine and impact abstinence in cocaine dependence. Therefore, we conducted a double-blind placebo-controlled pilot trial of acamprosate for the treatment of cocaine dependence.

METHODS

Sixty male and female cocaine dependent patients were included in a nine week double-blind, placebo-controlled trial. After a one-week baseline, patients were randomized to receive acamprosate 666 mg three times daily or identical placebo tablets for eight weeks. The primary outcome measure was cocaine use as determined by twice weekly urine drug screens.

RESULTS

Thirty-six patients (60%) completed the trial, with no significant between-group difference in treatment retention. Percent cocaine positive urine drug screens did not differ between the two groups. Acamprosate was no better than placebo in reducing cocaine craving, reducing cocaine withdrawal symptoms, or improving measures of drug use severity from the Addiction Severity Index. Adverse events in this trial were generally mild and were evenly distributed between the two groups.

DISCUSSION

Acamprosate was well tolerated but was no more efficacious than placebo in promoting abstinence from cocaine in cocaine dependent patients. Acamprosate does not appear to be a promising medication for the treatment of cocaine dependence.

Acamprosate reduces ethanol drinking behaviors and alters the metabolite profile in mice lacking ENT1

Acamprosate is clinically used to treat alcoholism. However, the precise molecular functionality of acamprosate in the central nervous system remains unclear, although it is known to antagonize glutamate action in the brain. Since elevated glutamate signaling, especially in the nucleus accumbens (NAc), is implicated in several aspects of alcoholism, we utilized mice lacking type 1 equilibrative nucleoside transporter (ENT1), which exhibit increased glutamate levels in the NAc as well as increased ethanol drinking behaviors. We found that acamprosate significantly reduced ethanol drinking of mice lacking ENT1 (ENT1(-/-)) while having no such effect in wild-type littermates. We then analyzed the basal and acamprosate-treated accumbal metabolite profiles of ENT1(-/-) and wild-type mice using in vivo 16.4T proton magnetic resonance spectroscopy (MRS). Our data show that basal glutamate+glutamine (Glx), glutamate, glutamine and N-acetylaspartatic acid (NAA) levels are increased in the nucleus accumbens (NAc) of ENT1(-/-) compared to wild-type mice. We then found that acamprosate treatment significantly reduced Glx and glutamine levels while increasing taurine levels in the NAc of only ENT1(-/-) compared to their saline-treated group while normalizing other metabolite compared to wild-type mice. This study will be useful in the understanding of the molecular basis of acamprosate in the brain.

Neuroprotection by taurine in ethanol-induced apoptosis in the developing cerebellum

BACKGROUND

Acute ethanol administration leads to massive apoptotic neurodegeneration in the developing central nervous system. We studied whether taurine is neuroprotective in ethanol-induced apoptosis in the mouse cerebellum during the postnatal period.

METHODS

The mice were divided into three groups: ethanol-treated, ethanol+taurine-treated and controls. Ethanol (20% solution) was administered subcutaneously at a total dose of 5 g/kg (2.5 g/kg at time 1 h and 2.5 g/kg at 3 h) to the ethanol and ethanol+taurine groups. The ethanol+taurine group also received two injections of taurine (1 g/kg each, at time zero and at 4 h). To estimate apoptosis, immunostaining for activated caspase-3 and TUNEL staining were made in the mid-sagittal sections containing lobules I-X of the cerebellar vermis at 12 or 8 hours after the first taurine injection. Changes in the blood taurine level were monitored at each hour by reverse-phase high-performance liquid chromatography (HPLC).

RESULTS

Ethanol administration induced apoptosis of Purkinje cells on P4 in all cerebellar lobules, most extensively in lobules IX and X, and on P7 increased the number of activated caspase-3-immunoreactive and TUNEL-positive cells in the internal layer of the cerebellum. Administration of taurine significantly decreased the number of activated caspase-3-immunoreactive and TUNEL-positive cells in the internal layer of the cerebellum on P7, but had no effect on Purkinje cells in P4 mice. The high initial taurine concentration in blood of the ethanol+taurine group diminished dramatically during the experiment, not being different at 13 h from that in the controls.

CONCLUSIONS

We conclude that the neuroprotective action of taurine is not straightforward and seems to be different in different types of neurons and/or requires prolonged maintenance of the high taurine concentration in blood plasma.

Role of altered structure and function of NMDA receptors in development of alcohol dependence

Long-term alcohol exposure gives rise to development of physical dependence on alcohol in consequence of changes in certain neurotransmitter functions. Accumulating evidence suggests that the glutamatergic neurotransmitter system, especially the N-methyl-D-aspartate (NMDA) type of glutamate receptors is a particularly important site of ethanol's action, since ethanol is a potent inhibitor of the NMDA receptors (NMDARs) and prolonged ethanol exposition leads to a compensatory "upregulation" of NMDAR mediated functions supposedly contributing to the occurrence of ethanol tolerance, dependence as well as the acute and delayed signs of ethanol withdrawal.Recently, expression of different types of NMDAR subunits was found altered after long-term ethanol exposure. Especially, the expression of the NR2B and certain splice variant forms of the NR1 subunits were increased in primary neuronal cultures treated intermittently with ethanol. Since NMDA ion channels with such an altered subunit composition have increased permeability for calcium ions, increased agonist sensitivity, and relatively slow closing kinetics, the abovementioned alterations may underlie the enhanced NMDAR activation observed after long-term ethanol exposure. In accordance with these changes, the inhibitory potential of NR2B subunit-selective NMDAR antagonists is also increased, demonstrating excellent potency against alcohol withdrawal-induced in vitro cytotoxicity. Although in vivo data are few with these compounds, according to the effectiveness of the classic NMDAR antagonists in attenuation, not only the physical symptoms, but also some affective and motivational components of alcohol withdrawal, novel NR2B subunit selective NMDAR antagonists may offer a preferable alternative in the pharmacotherapy of alcohol dependence.

Cocaine-induced neuroadaptations in glutamate transmission: potential therapeutic targets for craving and addiction

A growing body of evidence indicates that repeated exposure to cocaine leads to profound changes in glutamate transmission in limbic nuclei, particularly the nucleus accumbens. This review focuses on preclinical studies of cocaine-induced behavioral plasticity, including behavioral sensitization, self-administration, and the reinstatement of cocaine seeking. Behavioral, pharmacological, neurochemical, electrophysiological, biochemical, and molecular biological changes associated with cocaine-induced plasticity in glutamate systems are reviewed. The ultimate goal of these lines of research is to identify novel targets for the development of therapies for cocaine craving and addiction. Therefore, we also outline the progress and prospects of glutamate modulators for the treatment of cocaine addiction.

The neurobiology, clinical efficacy and safety of acamprosate in the treatment of alcohol dependence

IMPORTANCE TO THE FIELD

Acamprosate, marketed under the brand name Campral, (Forest Pharmaceuticals, Inc., Saint Louis, MO, USA; Merck Sante s.a.s., Lyon, France) is an orally administered drug approved in the US and throughout much of the world for treating alcohol dependence. Its safety and efficacy have been demonstrated in a number of clinical trials worldwide and as with all pharmacotherapies for alcoholism, it is used in conjunction with psychosocial interventions.

AREAS COVERED IN THIS REVIEW

This article reviews the mechanism of action, clinical efficacy and safety of acamprosate in Phase I, II and III randomized controlled trials involving healthy and alcohol-dependent populations using published reports from 1984 to 2009.

WHAT THE READER WILL GAIN

This review provides an update of the mechanism of action and the safety and efficacy profile of acamprosate.

TAKE HOME MESSAGE

Acamprosate appears to act centrally to restore the normal activity of glutamatergic neurotransmission altered by chronic alcohol exposure. Acamprosate's excellent safety profile along with several pharmacokinetic and pharmacodynamic characteristics make it well suited for treating a broad population of alcohol-dependent patients.

Intermittent high-dose ethanol exposures increase motivation for operant ethanol self-administration: possible neurochemical mechanism

We investigated the neurochemical mechanism of how high-dose ethanol exposure may increase motivation for ethanol consumption. First, we developed an animal model of increased motivation for ethanol using a progressive ratio (PR) schedule. Sprague-Dawley rats were trained to administer 10% ethanol-containing gelatin or plain gelatin (on alternate weeks) in daily 30-min sessions under different fixed ratio (FR) and PR schedules. During FR schedules, rats self-administered about 1 g/kg ethanol, which was decreased to 0.4+/-0.03 g/kg under PR10. Rats then received four pairs of either 3 g/kg ethanol or saline injections during the weeks when the reinforcer was plain gelatin. During subsequent ethanol gel sessions, breakpoints and ethanol consumption rose 40% in the high-dose ethanol group by the fourth set of injections with no change in plain gel responding. Alterations in amino acids in the ventral striatum (VS) during PR10 responding for 10% ethanol gelatin and plain gelatin were measured using microdialysis sampling coupled with capillary electrophoresis and laser-induced fluorescence detection. There was greater release of taurine, glycine and glutamate in the NAC of the high-dose ethanol rats during 10% ethanol-containing gelatin responding, compared to the control rats or during plain gel responding. An increase in the release of glycine in this same brain region has recently been shown to be involved with anticipation of a reward. Thus, it appears that intermittent high-dose ethanol exposure not only increases motivation for ethanol responding but may also change neurotransmitter release that mediates anticipation of reinforcement, which may play a key role in the development of alcoholism.

Aminophylline (a theophylline-ethylenediamine complex) blocks ethanol behavioral effects in mice

Aminophylline is a complex of theophylline-ethylenediamine, where theophylline is the main component. Theophylline is a methyxanthine and besides inhibiting phosphodiesterase enzymes, it is also a nonselective adenosine antagonist. Several reports suggested the involvement of the brain adenosinergic system in the ethanol-induced motor incoordination. Thus, the objective of this work was to study the effects of the interaction of ethanol with aminophylline as assessed by behavioral tests in mice. Eight groups of male Swiss mice were used. The animals were treated with either distilled water (control) or ethanol (E; 2, 4, and 6 g/kg, orally) for 5 days, or with distilled water for 4 days, and on the fifth day with aminophylline (A; 5 and 10 mg/kg, intraperitoneally). In the association groups (association protocols), the animals were treated with ethanol (E; 6 g/kg, orally) for 4 days, and on the fifth day received aminophylline (A; 10 mg/kg, intraperitoneally), 30 min after the last ethanol administration (first protocol, E/A). In the second association protocol (A/E), ethanol was administered for 4 days, and on the fifth day the animals received aminophylline (A; 10 mg/kg, intraperitoneally), followed again by ethanol (E; 6 g/kg, orally) administration, 30 min later. E (6 g/kg) evoked a central nervous system depressor effect, by decreasing both the locomotor activity and rearing in the open field test, and A (5 and 10 mg/kg) showed opposite effects. However, the E/A or A/E associations blocked the ethanol effect. In the rota rod test, ethanol presented a muscular relaxant effect, which was decreased in both association protocols. In the tail suspension test, while the E/A association decreased immobility, A/E association increased it, as compared with controls. In conclusion, the effects of ethanol were inhibited by its association with aminophylline, suggesting that ethanol acts on the adenosine neurotransmission.

Glycine receptor expression in the forebrain of male AA/ANA rats

Ethanol is known to directly interact with the glycine receptor (GlyR). GlyRs are membrane proteins and are constituted as either alpha-homomers or alpha-beta heteromers with a subunit stoichiometry of 2 alpha 3 beta. Previous studies by our group have suggested a role for GlyRs and its endogenous ligands glycine and taurine in the mesolimbic dopamine activating and reinforcing effects of ethanol. Here we use quantitative PCR (qPCR) to compare the relative GlyR expression in Alko Alcohol/Non-Alcohol (AA/ANA) rats. These animals have been selectively bred to create distinct populations regarding alcohol consumption and preference, presumably mainly due to genetic differences. The aim of this study was to examine the relative gene expression of GlyR subunits (alpha1-3 and beta) in different brain areas and relate it to alcohol consumption. The hypothesis was that AA/ANA rats are differently disposed to ethanol consumption due to their GlyR set-ups and/or compositions. Results from the present study indicate that alpha2 is the most widely expressed alpha-subunit in the forebrain regions and that the alpha 2 beta-heteromer seems to be the most common subunit composition in this part of the CNS. Despite displaying different drinking behaviours the anticipated differences in mRNA expression were few. However, correlations found between alcohol consumption and/or preference and GlyR expression support a role for GlyRs in alcohol consumption. Tentative differences between AA and ANA animals related to GlyR transmission could therefore lie in, for example, the regulation of the levels of the endogenous ligand(s) for the receptor or in mechanisms downstream to GlyR activation.

Initiating acamprosate within-detoxification versus post-detoxification in the treatment of alcohol dependence

OBJECTIVES

This trial compared the efficacy of acamprosate, started at the beginning of detoxification, to acamprosate started at the completion of detoxification, in the treatment of alcohol dependence.

METHODS

This biphasic clinical trial consisted of a randomized, double-blind, placebo-controlled Detoxification Phase (DP), followed by a 10-week open-label Rehabilitation Phase (RP). Forty alcohol dependent patients were randomly assigned to receive either 1998 mg of acamprosate daily, or matching placebo, during the DP (5-14 days). After completing detoxification, all patients received open label acamprosate (1998 mg daily) in the RP. Outcome measures during the DP included: treatment retention, alcohol withdrawal, alcohol consumption, and oxazepam used. Outcome measures during the RP included: treatment retention and alcohol consumption.

RESULTS

There were no significant outcome differences between acamprosate and placebo-treated patients during the DP. Patients given acamprosate, compared to placebo, during the DP drank more alcohol in the RP.

CONCLUSIONS

Starting acamprosate at the beginning of detoxification did not improve DP outcomes. Starting acamprosate after detoxification was completed was associated with better drinking outcomes during subsequent alcohol rehabilitation treatment.

Association of single nucleotide polymorphisms in a glutamate receptor gene (GRM8) with theta power of event-related oscillations and alcohol dependence

Evidence suggests the P3 amplitude of the event-related potential and its underlying superimposed event-related oscillations (EROs), primarily in the theta (4-5 Hz) and delta (1-3 Hz) frequencies, as endophenotypes for the risk of alcoholism and other disinhibitory disorders. Major neurochemical substrates contributing to theta and delta rhythms and P3 involve strong GABAergic, cholinergic and glutamatergic system interactions. The aim of this study was to test the potential associations between single nucleotide polymorphisms (SNPs) in glutamate receptor genes and ERO quantitative traits. GRM8 was selected because it maps at chromosome 7q31.3-q32.1 under the peak region where we previously identified significant linkage (peak LOD = 3.5) using a genome-wide linkage scan of the same phenotype (event-related theta band for the target visual stimuli). Neural activities recorded from scalp electrodes during a visual oddball task in which rare target elicited P3s were analyzed in a subset of the Collaborative Study on the Genetics of Alcoholism (COGA) sample comprising 1,049 Caucasian subjects from 209 families (with 472 DSM-IV alcohol dependent individuals). The family-based association test (FBAT) detected significant association (P < 0.05) with multiple SNPs in the GRM8 gene and event-related theta power to target visual stimuli, and also with alcohol dependence, even after correction for multiple comparisons by false discovery rate (FDR). Our results suggest that variation in GRM8 may be involved in modulating event-related theta oscillations during information processing and also in vulnerability to alcoholism. These findings underscore the utility of electrophysiology and the endophenotype approach in the genetic study of psychiatric disorders.

Breath alcohol level and plasma amino acids: a comparison between older and younger chronic alcohol-dependent patients

AIM

The aim of the present study is to examine the distribution of plasma excitatory and inhibitory amino acids, according to the age and current breath alcohol levels (BrAl+/-), of alcohol-dependent patients.

PARTICIPANTS AND METHODS

78 alcohol-dependent patients (mean age=46.2+/-11 years, men/women=54/24) were clinically tested, including the determination of the major excitatory as well as inhibitory amino acids. The independent variables were gender, age and current alcohol consumption measured with the breath alcohol level (BrAl+/-status).

RESULTS

In comparison to BrAl negatives, BrAl positives had higher plasma levels of glutamic acid (P=0.01) and proline (P=0.026), and lower levels of aminobutyric acid (P=0.002), serine (P=0.031) and urea (P=0.01). In the BrAl positives, no age effect was found related to the plasma amino acids. In contrast, the BrAl negatives displayed age-related differences. The older (>or=50 years) BrAl negative patients had higher plasma levels of cystine, tyrosine, citrulline and urea, and lower histidine levels, compared to the younger group (<50 years). In general, differences in plasma levels of certain amino acids were dependent on gender, BrAl status, age and biochemical markers (GGT, MCV) of alcohol abuse.

CONCLUSIONS

Abstaining patients (BrAl-/) display age-related differences in AAs' distribution, while active drinking (BrAl+/) seems to even out those differences, underpinning the hypothesis that drinking mimics changes seen with advanced age.

Determination of amino acid levels in the rat striatum, after administration of ethanol alone and associated with ketamine, a glutamatergic antagonist

The main goal of this study was to determine the amino acids (glutamate, aspartate, glutamine and tyrosine) levels in the rat striatum, after ethanol administration alone and/or associated with ketamine. In protocol 1 (Et+ketamine-1), ethanol was administered to male Wistar rats until the 7th day, and at the next day the group received only ketamine (25mg/kg, i.p.) up to the 14th day. In protocol 2 (Et+ketamine-2), ethanol was also administered up to the 7th day, and was associated with ketamine from the 8th up to the 14th day. In other groups, animals were treated daily with ethanol (4 g/kg, p.o.), for 7 or 14 days or ketamine daily for 7 days. Controls were administered with distilled water for 7 days. Results showed that, in protocol 1, aspartate (ASP) levels increased after ketamine administration, as compared to the controls. This effect was inhibited in the group Et+ketamine-1. Ethanol (7 days) increased glutamate (GLU) levels, as compared to control, and this effect did not differ significantly from that observed in the ketamine group. When ketamine was administered after the ethanol withdrawal (protocol 1), no alterations in those amino acid concentrations were seen, as compared to the control and ketamine groups. A tendency for increasing GLU levels was observed, after administration of ethanol (14 days) or ketamine alone or associated (protocol 2), when compared to control values. In protocol 2, TYR levels decreased as related to controls and to the 14-day ethanol-treated group. We can assume that ketamine presents only an antagonist effect, in animals pretreated with ethanol, followed by ketamine administered from the 8th day on. This is due to the fact that NMDA receptors are already sensitized, leading to a decrease in these receptors functions and consequently to ASP and GLU releases.

High temporal resolution of amino acid levels in rat nucleus accumbens during operant ethanol self-administration: involvement of elevated glycine in anticipation

Capillary electrophoresis coupled with laser-induced fluorescence detection (CE-LIF) provides 15-s temporal resolution of amino acid levels in microdialysate, which, for the first time, allows almost real time measurement of changes during episodes of behavior. We trained Sprague-Dawley rats to self-administer either 10% ethanol-containing gelatin or non-alcoholic gelatin in a typical operant chamber. After rats reached stable daily levels of responding, microdialysis probes were inserted into nucleus accumbens and samples were collected before, during and after operant sessions with on-line analysis via CE-LIF. During the first 15 min of the operant session, there was a significant increase in taurine that correlated with the amount of ethanol consumed (R(2)=0.81) but no change in rats responding for plain gel. There were large, consistent increases in glycine in both the ethanol and plain gel groups which correlated with the amount of gel consumed. A smaller increase was observed in rats with free non-operant access to plain gel compared to the increase seen with the same amount of gel consumed under operant conditions. When rats were given a time out after each delivery of gel in the operant protocol, the greatest increase of glycine was obtained with the longest time out period. Thus, increases in glycine in nucleus accumbens appear to be related to anticipation of reinforcement.

Uncovering genes for cognitive (dys)function and predisposition for alcoholism spectrum disorders: a review of human brain oscillations as effective endophenotypes

Brain oscillations provide a rich source of potentially useful endophenotypes (intermediate phenotypes) for psychiatric genetics, as they represent important correlates of human information processing and are associated with fundamental processes from perception to cognition. These oscillations are highly heritable, are modulated by genes controlling neurotransmitters in the brain, and provide links to associative and integrative brain functions. These endophenotypes represent traits that are less complex and more proximal to gene function than either diagnostic labels or traditional cognitive measures, providing a powerful strategy in searching for genes in psychiatric disorders. These intermediate phenotypes identify both affected and unaffected members of an affected family, including offspring at risk, providing a more direct connection with underlying biological vulnerability. Our group has utilized heritable neurophysiological features (i.e., brain oscillations) as endophenotypes, making it possible to identify susceptibility genes that may be difficult to detect with diagnosis alone. We have discussed our findings of significant linkage and association between brain oscillations and genes in GABAergic, cholinergic and glutamatergic systems (GABRA2, CHRM2, and GRM8). We have also shown that some oscillatory indices from both resting and active cognitive states have revealed a common subset of genetic foci that are shared with the diagnosis of alcoholism and related disorders. Implications of our findings have been discussed in the context of physiological and pharmacological studies on receptor function. These findings underscore the utility of quantitative neurophysiological endophenotypes in the study of the genetics of brain function and the genetic diathesis underlying complex psychiatric disorders.

Acamprosate attenuates the handling induced convulsions during alcohol withdrawal in Swiss Webster mice

In the present study, we examined the effects of acamprosate for its ability to reduce handling induced convulsions (HICs) during alcohol withdrawal. Diazepam was used as a positive control. Swiss Webster male mice received three daily IP injections of alcohol (2.5 g/kg) or alcohol (2.5 g/kg)+methylpyrazole (4-MP) (9 mg/kg). (4-MP, being an alcohol dehydrogenase inhibitor slows down the breakdown of alcohol. 4-MP in combination with alcohol exhibits a dramatic increase in blood alcohol level compared to alcohol alone). Ten hours following the last alcohol injection, the mice were picked up by the tail and examined for their seizure susceptibility (HICs). Diazepam, a benzodiazepine known to reduce seizures during alcohol withdrawal, significantly reduced these HICs at doses of 0.25, 0.5 and 1 mg/kg (p's<0.001). Acamprosate, an anti-relapse compound used clinically in newly abstinent alcoholics, also reduced these HICs at doses of 100, 200 and 300 mg/kg (p's<0.05). This study supports the use of acamprosate during periods of alcohol withdrawal as well as during abstinence.

Glutamatergic substrates of drug addiction and alcoholism

The past two decades have witnessed a dramatic accumulation of evidence indicating that the excitatory amino acid glutamate plays an important role in drug addiction and alcoholism. The purpose of this review is to summarize findings on glutamatergic substrates of addiction, surveying data from both human and animal studies. The effects of various drugs of abuse on glutamatergic neurotransmission are discussed, as are the effects of pharmacological or genetic manipulation of various components of glutamate transmission on drug reinforcement, conditioned reward, extinction, and relapse-like behavior. In addition, glutamatergic agents that are currently in use or are undergoing testing in clinical trials for the treatment of addiction are discussed, including acamprosate, N-acetylcysteine, modafinil, topiramate, lamotrigine, gabapentin and memantine. All drugs of abuse appear to modulate glutamatergic transmission, albeit by different mechanisms, and this modulation of glutamate transmission is believed to result in long-lasting neuroplastic changes in the brain that may contribute to the perseveration of drug-seeking behavior and drug-associated memories. In general, attenuation of glutamatergic transmission reduces drug reward, reinforcement, and relapse-like behavior. On the other hand, potentiation of glutamatergic transmission appears to facilitate the extinction of drug-seeking behavior. However, attempts at identifying genetic polymorphisms in components of glutamate transmission in humans have yielded only a limited number of candidate genes that may serve as risk factors for the development of addiction. Nonetheless, manipulation of glutamatergic neurotransmission appears to be a promising avenue of research in developing improved therapeutic agents for the treatment of drug addiction and alcoholism.

Acamprosate attenuates cocaine- and cue-induced reinstatement of cocaine-seeking behavior in rats

RATIONALE

Acamprosate (calcium acetylhomotaurinate) is a glutamatergic neuromodulator used for the treatment of alcoholism, but its potential efficacy in the treatment of psychostimulant addiction has not been explored.

OBJECTIVES

The purpose of this study was to assess the effects of acamprosate on cocaine-stimulated locomotor activity, cocaine self-administration, and cue- and cocaine-induced reinstatement of cocaine-seeking behavior.

MATERIALS AND METHODS

All experiments utilized once-daily treatment for 5 consecutive days. First, the effects of saline or acamprosate (100, 300, or 500 mg/kg intraperitoneally) on body weight were examined. On the last day of treatment, locomotor activity was assessed before and after drug treatment, after which all animals received an acute challenge of cocaine (10 mg/kg). Next, a separate group of rats were trained to intravenously (IV) self-administer cocaine (0.6 mg/kg per infusion), subjected to extinction procedures, and then tested for effects of acamprosate on cue- or cocaine-induced reinstatement. A third group of rats was trained to self-administer cocaine as described above and were treated with saline or acamprosate before daily IV self-administration sessions.

RESULTS

Repeated administration of 500 mg/kg acamprosate but not lower doses produced reductions in both body weight and spontaneous locomotor activity, and thus this dose was not tested further. Acamprosate at 300 mg/kg but not 100 mg/kg attenuated both cocaine- and cue-induced reinstatement without altering baseline patterns of cocaine self-administration or cocaine-stimulated hyperlocomotion.

CONCLUSIONS

Acamprosate attenuates both drug- and cue-induced reinstatement of cocaine-seeking behavior, suggesting that this compound may serve as a potential treatment for preventing relapse in cocaine-addicted humans.

A pilot double-blind treatment trial of memantine for alcohol dependence

BACKGROUND

There is growing evidence that N-methyl-d-aspartate (NMDA) receptor antagonists may have potential for the treatment of alcohol disorders. Memantine is a selective noncompetitive NMDA receptor antagonist that has been shown to decrease alcohol craving in moderate drinkers. This 16-week double-blind outpatient pilot clinical trial determined if memantine was more effective than placebo at reducing alcohol use in actively drinking alcohol-dependent patients.

METHODS

Forty-four treatment-seeking alcohol-dependent individuals were enrolled, with 34 patients stratified to either the memantine group (n=19; maximum dose of 40 mg/d) or the placebo (PBO; n=15) group. The primary outcome measures were related to alcohol use (average drinks per day, average drinks per drinking day, percentage of heavy drinking days, and percentage of days abstinent) based on the timeline follow-back (TLFB). Secondary outcome measures included the Obsessive Compulsive Drinking Scale, Clinical Global Impression ratings, and gamma-glutamyltransferase (GGT), a biomarker of recent alcohol use. To enhance retention, patients received voucher incentives for clinic attendance.

RESULTS

Of those randomized, approximately 80% (27) completed the entire 16-week trial. Longitudinal analysis of drinks per day and drinks per drinking day showed a significant reduction in alcohol use, but no difference between the 2 groups. Further, the percentage of heavy drinking days indicated that both groups showed a significant decrease in drinking behavior, but there was significant treatment effect in favor of the PBO group. Similarly, for the percentage of days abstinent, the PBO group achieved a significantly greater percentage of days abstinent at a faster rate than the memantine group. Lastly, the memantine group reported a greater number of side effects compared with the PBO group, such that 26% of patients had their drug dose decreased or discontinued due to memantine-related side effects.

CONCLUSIONS

The results of this double-blind placebo-controlled pilot trial do not support the use of memantine for the treatment of actively drinking alcohol-dependent patients. However, voucher incentives did facilitate retention.

Ethanol and acetaldehyde induce similar changes in extracellular levels of glutamate, taurine and GABA in rat anterior cingulate cortex

It is controversial regarding to the roles of acetaldehyde and ethanol in the central nervous system. In the present study, the effects of acetaldehyde and ethanol on extracellular levels of glutamate, taurine and GABA in the anterior cingulate cortex (ACC) of freely moving rats were investigated by using the microdialysis technique coupled to high performance liquid chromatography (HPLC) with fluorescent detection. The result showed that glutamate levels were significantly decreased after acute administration of acetaldehyde (AcH, 20 and 100 mg/kg, i.p.), while taurine levels were significantly increased after the higher dose of acetaldehyde (100 mg/kg, i.p.). GABA levels had no changes at any doses of acetaldehyde tested. Interestingly, similar changes of these amino acids were induced by ethanol (EtOH, 3 g/kg, i.p.) when sodium azide (NaN3, 10 mg/kg, i.p.), a catalase inhibitor that can reduce brain ethanol metabolism, was used simultaneously. These findings suggest that acetaldehyde and ethanol have the similar effects on the extracellular output of glutamate, taurine and GABA in the ACC.