Valentina Vengeliene

Involvement of the AMPA Receptor GluR-C Subunit in Alcohol-Seeking Behavior and Relapse

Craving and relapse are core symptoms of drug addiction and alcoholism. It is suggested that, after chronic drug consumption, long-lasting neuroplastic changes within the glutamatergic system are important determinants of addictive behavior. Here, we show that the AMPA type glutamate receptor plays a crucial role in alcohol craving and relapse. We observed, in two animal models of alcohol craving and relapse, that the AMPA antagonist GYKI 52466 [1-(4-aminophenyl)-4-methyl-7, 8-methylenedioxy-5H-2, 3-benzodiazepine] dose-dependently reduced cue-induced reinstatement of alcohol-seeking behavior and the alcohol deprivation effect. The involvement of the AMPA receptor in these phenomena was further studied using mice deficient for the GluR-C AMPA subunit [GluR-C knock-out (KO)]. GluR-C KOs displayed a blunted, cue-induced reinstatement response and alcohol deprivation effect, when compared with wild-type controls; however, no differences between genotypes could be observed regarding ethanol self-administration under operant or home cage drinking conditions. These results imply a role for GluR-C in alcohol relapse, although this phenotype could also be attributable to a reduction in the total number of AMPA receptors in specific brain areas. In conclusion, AMPA receptors seem to be involved in the neuroplastic changes underlying alcohol seeking behavior and relapse. Thus, AMPA receptors represent a novel therapeutic target in preventing relapse.

Influence of age at drinking onset on long-term ethanol self-administration with deprivation and stress phases.

BACKGROUND Onset of alcohol use during adolescence has potentially long-lasting consequences, e.g., prospective alcohol dependence. To obtain new insight into the effects of early chronic ethanol consumption, we compared the drinking behavior of two adult male Wistar rat groups: one that initiated alcohol consumption during adolescence (adolescent group) and the other that initiated their drinking during adulthood (adult group) in a model of long-term alcohol self-administration. We investigated the magnitude of the effects of deprivation and stress on alcohol intake and the influence of these events on the alcohol drinking behavior across time. METHODS Heterogeneous Wistar rats aged 31 days (adolescents) and 71 days (adults) were given ad libitum access to water, as well as 5% and 20% ethanol solutions during an observation period of 30 wk. A deprivation phase of 14 days was instituted after eight wk of access to alcohol. After 16 and 26 wk of alcohol access, all animals were subjected for three consecutive days to forced swimming and electric foot shocks, respectively. RESULTS At the onset of drinking, adolescent animals consumed less alcohol and showed lower preference than adults. The deprivation phase was followed by increased intake of highly concentrated ethanol solution without appreciable differences between age groups. Repeated swim stress produced a slight increase in ethanol consumption in both animal groups; however, alcohol intake was not significantly different between groups, whereas the foot shock stress-induced increase in alcohol intake was significantly higher in the animal group that initiated alcohol consumption during adolescence. After swim stress, the drinking behavior of the adolescent group resembled that of the adult group. In particular, the adolescent group increased their preference for 20% ethanol solution for the remainder of the experiment. CONCLUSIONS Age of voluntary alcohol drinking onset does not appear to be a strong predictor for prospective alcohol intake and relapse-like drinking behavior under the present experimental conditions. However, male Wistar rats that initiated alcohol consumption during adolescence seem to be more susceptible to acute stressor-specific effects in terms of alcohol consumption.

Effect of Acamprosate on Magnetic Resonance Spectroscopy Measures of Central Glutamate in Detoxified Alcohol-Dependent Individuals A Randomized Controlled Experimental Medicine Study

CONTEXT Acamprosate is approved for the treatment of alcoholism, but its mechanism of action remains unclear. Results of animal studies suggest that a persistent hyperglutamatergic state contributes to the pathogenesis of alcoholism and that acamprosate may exert its actions by intervening in this process. Human translation of these findings is lacking. OBJECTIVE To examine whether acamprosate modulates indices of central glutamate levels in recently abstinent alcohol-dependent patients as measured using proton nuclear magnetic resonance spectroscopy (¹H-MRS). DESIGN A 4-week, double-blind, placebo-controlled, randomized controlled experimental medicine study, with ¹H-MRS measures obtained on days 4 and 25. SETTING An inpatient research unit at the NIH Clinical Center. Patients Thirty-three patients who met the DSM-IV criteria for alcohol dependence and who were admitted for medically supervised withdrawal from ongoing alcohol use. Intervention Four weeks of acamprosate (initial oral loading followed by 1998 mg daily) or matched placebo, initiated at the time of admission. MAIN OUTCOME MEASURES The glutamate to creatine ratio as determined using single-voxel ¹H-MRS in the anterior cingulate. Exploratory neuroendocrine, biochemical, and behavioral outcomes were also collected, as were safety- and tolerability-related measures. RESULTS There was a highly significant suppression of the glutamate to creatine ratio across time by acamprosate (time × treatment interaction: F₁(,)₂₉ = 13.5, P < .001). Cerebrospinal fluid levels of glutamate obtained in a subset of patients 4 weeks into abstinence were uncorrelated with the MRS measures and unaffected by treatment but were strongly correlated (R² = 0.48, P < .001) with alcohol dependence severity. Other exploratory outcomes, including repeated dexamethasone-corticotropin-releasing hormone tests, and psychiatric ratings were unaffected. Among tolerability measures, gastrointestinal symptoms were significantly greater in acamprosate-treated individuals, in agreement with the established profile of acamprosate. CONCLUSION The MRS measures of central glutamate are reduced across time when acamprosate therapy is initiated at the onset of alcohol abstinence. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00106106.

Rats with congenital learned helplessness respond less to sucrose but show no deficits in activity or learning.

Inbred rat strains for congenital learned helplessness (cLH) and for congenital resistance to learned helplessness (cNLH) were investigated as a model to study genetic predisposition to major depression. Congenitally helpless rats respond less to sucrose under a progressive ratio schedule. This is not confounded by locomotor hypoactivity: in contrast, cLH rats show a slight hyperactivity during the first 5 min of an open field test. cLH rats acquire operant responding to sucrose as readily as cNLH rats and exhibit normal memory acquisition and retrieval in the Morris water maze, thus ruling out general learning deficits as the cause of the decreased response to sucrose. Reduced total responses and reduced breaking points for sucrose in the cLH strain argue for anhedonia, which is an analogue to loss of pleasure essential for the diagnosis of major depressive episodes, and thus confirm the validity of congenitally learned helpless rats as a model of major depression.

The dopamine D3 receptor plays an essential role in alcohol-seeking and relapse

Our study aimed to identify new candidate genes, which might be involved in alcohol craving and relapse. To find changes in gene expression after long‐term alcohol consumption, we studied gene expression profiles in the striatal dopamine system by using DNA microarrays of two different alcohol‐preferring rat lines (HAD and P). Our data revealed an up‐regulation of the dopamine D3 receptor (D3R) after 1 yr of voluntary alcohol consumption in the striatum of alcohol preferring rats that was confirmed by qRT‐polymerase chain reaction. This finding was further supported by the finding of up‐regulated striatal D3R mRNA in nonselected Wistar rats after long‐term alcohol consumption when compared with age‐matched control animals. We further examined the role of the D3R in mediating alcohol relapse behavior using the alcohol deprivation effect (ADE) model in long‐term alcohol drinking Wistar rats and the model of cue‐induced reinstatement of alcohol‐seeking behavior using the selective D3R antagonist SB‐277011‐A (0, 1, 3, and 10 mg/kg) and the partial agonist BP 897 (0, 0.1, 1, and 3 mg/kg). Both treatments caused a dose‐dependent reduction of relapse‐like drinking in the ADE model as well as a decrease in cue‐induced ethanol‐seeking behavior. We conclude that long‐term alcohol consumption leads to an up‐regulation of the dopamine D3R that may contribute to alcohol‐seeking and relapse. We therefore suggest that selective antagonists of this pharmacological target provide a specific treatment approach to reduce alcohol craving and relapse behavior.—Vengeliene, V., Leonardi‐Essmann, F., Perreau‐Lenz, S., Gebicke‐Haerter, P., Drescher, K., Gross, G., Spanagel, R. The dopamine D3 receptor plays an essential role in alcohol‐seeking and relapse. FASEB J. 20, 2223–2233 (2006)

Compulsive alcohol drinking in rodents

Upon prolonged alcohol exposure, the behaviour of an individual can gradually switch from controlled to compulsive. Our review is focused on the neurobiological mechanisms that might underlie this transition as well as the factors that are influencing it. Animal studies suggest that temporally increased alcohol consumption during post‐abstinence drinking is accompanied by a loss of flexibility of the behaviour and therefore, could serve as a model for compulsive alcohol drinking. However, studies using different alcohol‐preferring rat lines in the post‐abstinence drinking model suggest that high alcohol consumption does not necessarily lead to the development of compulsive drinking. This indicates the significance of genetic predisposition to compulsive behaviour. Neuroimaging data show that chronic alcohol consumption affects the activity of several brain regions such as the extrapyramidal motor system and several areas of the prefrontal cortex including the orbitofrontal and anterior cingulate cortex. Similar changes in brain activity is seen in patients suffering from obsessive–compulsive disorder at baseline conditions and during provocation of obsessive thoughts and urge to perform compulsive‐like rituals. This indicates that dysfunction of these regions may be responsible for the expression of compulsive components of alcohol drinking behaviour. Several brain neurotransmitter systems seem to be responsible for the switch from controlled to compulsive behaviour. In particular, hypofunctioning of monoaminergic systems and hyperfunctioning of glutamatergic systems may play a role in compulsive alcohol drinking.

Influence of age at drinking onset on the alcohol deprivation effect and stress-induced drinking in female rats.

We have recently observed increased stress responsiveness with regard to alcohol consumption in male rats that consumed alcohol since their adolescent period. Thus, early age at drinking onset can induce enhanced stress-induced alcohol drinking in male rats. However, it is not known whether female rats respond in a similar way. Therefore, we compared the drinking behavior of two female Wistar rat groups--one that acquired alcohol consumption during adolescence (adolescent group) and the other that acquired their drinking during adulthood (adult group) in a model of long-term voluntary alcohol drinking with repeated deprivation and stress phases. Furthermore, we studied the influence of age at drinking onset on the efficacy of acamprosate treatment. Thirty-nine female Wistar rats aged 31 days (adolescents) and 71 days (adults) were given ad libitum access to water, as well as to 5% and 20% ethanol solutions during an observation period of 29 weeks. A deprivation phase of 14 days was introduced following 8 weeks of access to alcohol in order to measure the alcohol deprivation effect (ADE). After 15 and 25 weeks of alcohol access, all animals were subjected for 3 consecutive days of forced swim and electric foot-shock stress, respectively. After 29 weeks of access to alcohol all animals underwent a second deprivation phase and the subsequent ADE was measured either under acamprosate (200 mg/kg) or vehicle treatment. Drinking before the first deprivation phase was not different between animal groups. However, the expression of the first ADE was more pronounced in adult female rats and alcohol intake stayed increased for the remainder of the experiment in the adult group. Both repeated swim stress and foot-shock stress produced a more pronounced increase in ethanol consumption in the adolescent group compared to the adult group. Acamprosate reduced relapse-like drinking in the adult female rat group. However, it had no effect on the ADE in the adolescent group. In conclusion, female rats that initiate alcohol consumption during adolescence might be more susceptible to stress-induced alcohol consumption. Adolescent alcohol drinking might also result in a reduced response to acamprosate.

Acamprosate Produces Its Anti-Relapse Effects Via Calcium

Alcoholism is one of the most prevalent neuropsychiatric diseases, having an enormous health and socioeconomic impact. Along with a few other medications, acamprosate (Campral—calcium-bis (N-acetylhomotaurinate)) is clinically used in many countries for relapse prevention. Although there is accumulated evidence suggesting that acamprosate interferes with the glutamate system, the molecular mode of action still remains undefined. Here we show that acamprosate does not interact with proposed glutamate receptor mechanisms. In particular, acamprosate does not interact with NMDA receptors or metabotropic glutamate receptor group I. In three different preclinical animal models of either excessive alcohol drinking, alcohol-seeking, or relapse-like drinking behavior, we demonstrate that N-acetylhomotaurinate by itself is not an active psychotropic molecule. Hence, the sodium salt of N-acetylhomotaurinate (i) is ineffective in alcohol-preferring rats to reduce operant responding for ethanol, (ii) is ineffective in alcohol-seeking rats in a cue-induced reinstatement paradigm, (iii) and is ineffective in rats with an alcohol deprivation effect. Surprisingly, calcium salts produce acamprosate-like effects in all three animal models. We conclude that calcium is the active moiety of acamprosate. Indeed, when translating these findings to the human situation, we found that patients with high plasma calcium levels due to acamprosate treatment showed better primary efficacy parameters such as time to relapse and cumulative abstinence. We conclude that N-acetylhomotaurinate is a biologically inactive molecule and that the effects of acamprosate described in more than 450 published original investigations and clinical trials and 1.5 million treated patients can possibly be attributed to calcium.

The acute anti‐craving effect of acamprosate in alcohol‐preferring rats is associated with modulation of the mesolimbic dopamine system

Acamprosate (Campral ?) is a drug used clinically for the treatment of alcoholism. In order to examine further the time‐course and mechanism of action of acamprosate, the effect of acute and repeated acamprosate administration was examined on (i) operant ethanol self‐administration and (ii) voluntary home cage ethanol consumption by alcohol‐preferring Fawn‐Hooded, iP and Alko Alcohol (AA) rats. Acutely, acamprosate was shown to cause a significant decrease in operant ethanol self‐administration by Fawn‐Hooded and alcohol‐preferring iP rats in part by decreasing the motivational relevance of a specific ethanol cue; however, repeated injection of acamprosate led to tolerance to this effect. Voluntary alcohol consumption in the home cage in Fawn‐Hooded and AA rats was also reduced by an acute acamprosate injection; however, again tolerance developed to repeated injections. In a separate experiment, the effect of acamprosate on markers of the dopaminergic system was examined. Interestingly, acute acamprosate was also shown to cause increased dopamine transporter density and decreased dopamine D2‐like receptor density within the nucleus accumbens but not in the caudate‐putamen, suggesting a link between the decreased motivational salience of the ethanol cue and altered dopaminergic signalling within the nucleus accumbens. With repeated injections of acamprosate, markers of the dopaminergic system returned to steady state levels with a similar temporal profile to the development of tolerance in the behavioural studies. Along with previous studies, our findings indicate that acamprosate modulates the mesolimbic dopaminergic system and may thereby decrease ethanol reinforcement processes; however, these effects undergo tolerance in alcohol‐preferring rats and may in part explain the fact why some subjects are non‐responders to chronic acamprosate treatment.

A systems medicine research approach for studying alcohol addiction

According to the World Health Organization, about 2 billion people drink alcohol. Excessive alcohol consumption can result in alcohol addiction, which is one of the most prevalent neuropsychiatric diseases afflicting our society today. Prevention and intervention of alcohol binging in adolescents and treatment of alcoholism are major unmet challenges affecting our health‐care system and society alike. Our newly formed German SysMedAlcoholism consortium is using a new systems medicine approach and intends (1) to define individual neurobehavioral risk profiles in adolescents that are predictive of alcohol use disorders later in life and (2) to identify new pharmacological targets and molecules for the treatment of alcoholism. To achieve these goals, we will use omics‐information from epigenomics, genetics transcriptomics, neurodynamics, global neurochemical connectomes and neuroimaging (IMAGEN; Schumann et al. ) to feed mathematical prediction modules provided by two Bernstein Centers for Computational Neurosciences (Berlin and Heidelberg/Mannheim), the results of which will subsequently be functionally validated in independent clinical samples and appropriate animal models. This approach will lead to new early intervention strategies and identify innovative molecules for relapse prevention that will be tested in experimental human studies. This research program will ultimately help in consolidating addiction research clusters in Germany that can effectively conduct large clinical trials, implement early intervention strategies and impact political and healthcare decision makers.