Novel therapeutic strategies for alcohol and drug addiction: focus on GABA, ion channels and transcranial magnetic stimulation

GABAergic signaling in alcohol use disorder and withdrawal: pathological involvement and therapeutic potential

Alcohol is one of the most widely used substances. Alcohol use accounts for 5.1% of the global disease burden, contributes substantially to societal and economic costs, and leads to approximately 3 million global deaths yearly. Alcohol use disorder (AUD) includes various drinking behavior patterns that lead to short-term or long-lasting effects on health. Ethanol, the main psychoactive molecule acting in alcoholic beverages, directly impacts the GABAergic system, contributing to GABAergic dysregulations that vary depending on the intensity and duration of alcohol consumption. A small number of interventions have been developed that target the GABAergic system, but there are promising future therapeutic avenues to explore. This review provides an overview of the impact of alcohol on the GABAergic system, the current interventions available for AUD that target the GABAergic system, and the novel interventions being explored that in the future could be included among first-line therapies for the treatment of AUD.

Shared Mechanisms of GABAergic and Opioidergic Transmission Regulate Corticolimbic Reward Systems and Cognitive Aspects of Motivational Behaviors

The functional interplay between the corticolimbic GABAergic and opioidergic systems plays a crucial role in regulating the reward system and cognitive aspects of motivational behaviors leading to the development of addictive behaviors and disorders. This review provides a summary of the shared mechanisms of GABAergic and opioidergic transmission, which modulate the activity of dopaminergic neurons located in the ventral tegmental area (VTA), the central hub of the reward mechanisms. This review comprehensively covers the neuroanatomical and neurobiological aspects of corticolimbic inhibitory neurons that express opioid receptors, which act as modulators of corticolimbic GABAergic transmission. The presence of opioid and GABA receptors on the same neurons allows for the modulation of the activity of dopaminergic neurons in the ventral tegmental area, which plays a key role in the reward mechanisms of the brain. This colocalization of receptors and their immunochemical markers can provide a comprehensive understanding for clinicians and researchers, revealing the neuronal circuits that contribute to the reward system. Moreover, this review highlights the importance of GABAergic transmission-induced neuroplasticity under the modulation of opioid receptors. It discusses their interactive role in reinforcement learning, network oscillation, aversive behaviors, and local feedback or feedforward inhibitions in reward mechanisms. Understanding the shared mechanisms of these systems may lead to the development of new therapeutic approaches for addiction, reward-related disorders, and drug-induced cognitive impairment.

Association of GABA receptor delta subunit gene variations with increased risk of methamphetamine dependence

OBJECTIVE

Evidence reveals that γ-aminobutyric acid (GABA) receptors are involved in the development of methamphetamine (METH) dependence. The GABA receptor delta subunit gene (GABRD) might be a good candidate gene for METH dependence. In a case-control study, we investigated the association between the single nucleotide polymorphisms (SNPs) in GABRD and METH dependence in a Chinese Han population.

METHODS

A total of 300 METH dependent patients and 300 age and sex matched normal control subjects were recruited. Four SNPs (rs13303344, rs4481796, rs2376805, and rs2229110) in GABRD were determined with the TaqMan genotyping assay. The association of the SNPs with METH dependence was assessed.

RESULTS

Only the allele frequency of rs2376805 significantly differed between the patients and controls (P = 0.030). The G allele frequency of rs2376805 was higher in the METH dependent group than in the controls (odds ratio = 1.332, 95 % CI: 1.028-1.724). This association was found in females but not in males. In females, the frequencies of genotype and allele at rs2376805 significantly differed between the patients and controls (P = 0.025, 0.022, respectively); the rs2376805 G allele may also be a risk factor for METH dependence (odds ratio = 1.548, 95 % CI: 1.063-2.257). The haplotype ACGT frequency significantly differed between the patients and controls in total subjects (P = 0.008, odds ratio = 1.815, 95 % CI: 1.183-2.782), as well as in females (P = 0.005, odds ratio = 2.702, 95 % CI: 1.313-5.562). In females only, the METH craving score was significantly lower in patients harboring the G allele at rs2376805 than in those harboring the homozygous AA genotype (P = 0.044).

CONCLUSION

The preliminary results indicate that GABRD rs2376805 is associated with METH dependence, especially in females.

Therapeutics for Substance-Using Women: The Need to Elucidate Sex-Specific Targets for Better-Tailored Treatments

In the last decade, alcohol consumption in the US has risen by 84% in women compared with 35% in men. Furthermore, research has shown that sex- and gender-related differences may disadvantage women in terms of developing a range of psychological, cognitive, and medical problems considerably earlier in their drinking history than men, and despite consuming a similar quantity of substances. While this "telescoping" process has been acknowledged in the literature, a concomitant understanding of the underlying biobehavioral mechanisms, and an increase in the development of specific treatments tailored to women, has not occurred. In the current chapter we focus on understanding why the need for personalized, sex-specific medications is imperative, and highlight some of the potential sex-specific gonadal and stress-related adaptations underpinning the accelerated progress from controlled to compulsive drug and alcohol seeking in women. We additionally discuss the efficacy of these mechanisms as novel targets for medications development, using exogenous progesterone and guanfacine as examples. Finally, we assess some of the challenges faced and progress made in terms of developing innovative medications in women. We suggest that agents such as exogenous progesterone and adrenergic medications, such as guanfacine, may provide some efficacy in terms of attenuating stress-induced craving for several substances, as well as improving the ability to emotionally regulate in the face of stress, preferentially in women. However, to fully leverage the potential of these therapeutics in substance-using women, greater focus needs to the placed on reducing barriers to treatment and research by encouraging women into clinical trials.

Role of neuropeptide neuromedin U in the nucleus accumbens shell in cocaine self-administration in male rats

The nucleus accumbens shell (NAcSh) and its afferent and efferent neuronal projections control key aspects of motivation for cocaine. A recently described regulator of γ-aminobutyric acid (GABA) projections from the dorsal raphe nucleus (DRN) to the NAcSh (DRN → NAcSh) is the neuropeptide neuromedin U (NMU). Here, we find that systemic administration of NMU decreases breakpoint for cocaine on a progressive ratio schedule of reinforcement in male rats. Employing a retrograde adeno-associated virus (AAV), we found that RNAi-mediated knockdown of the NMU receptor 2 (NMUR2) in afferent DRN projections to the NAcSh increases the breakpoint for cocaine. Our previous studies demonstrated that NMU regulates GABA release in the NAcSh, and our current investigation found that systemic NMU administration suppresses cocaine-evoked GABA release in the NAcSh and increases phosphorylated c-Fos expression in neurons projecting from the NAcSh to the ventral pallidum (VP). To further probe the impact of NMU/NMUR2 on neuroanatomical pathways regulating motivation for cocaine, we employed multi-viral transsynaptic studies. Using a combination of rabies virus and retrograde AAV helper virus, we mapped the impact of NMU across three distinct brain regions simultaneously and found a direct connection of GABAergic DRN neurons to the NAcSh → VP pathway. Together, these data reveal that NMU/NMUR2 modulates a direct connection within the GABAergic DRN → NAcSh → VP circuit that diminishes breakpoints for cocaine. These findings importantly advance our understanding of the neurochemical underpinnings of pathway-specific regulation of neurocircuitry that may regulate cocaine self-administration, providing a unique therapeutic perspective.

Allosteric Modulators of Metabotropic Glutamate Receptors as Novel Therapeutics for Neuropsychiatric Disease

Metabotropic glutamate (mGlu) receptors, a family of G-protein-coupled receptors, have been identified as novel therapeutic targets based on extensive research supporting their diverse contributions to cell signaling and physiology throughout the nervous system and important roles in regulating complex behaviors, such as cognition, reward, and movement. Thus, targeting mGlu receptors may be a promising strategy for the treatment of several brain disorders. Ongoing advances in the discovery of subtype-selective allosteric modulators for mGlu receptors has provided an unprecedented opportunity for highly specific modulation of signaling by individual mGlu receptor subtypes in the brain by targeting sites distinct from orthosteric or endogenous ligand binding sites on mGlu receptors. These pharmacological agents provide the unparalleled opportunity to selectively regulate neuronal excitability, synaptic transmission, and subsequent behavioral output pertinent to many brain disorders. Here, we review preclinical and clinical evidence supporting the utility of mGlu receptor allosteric modulators as novel therapeutic approaches to treat neuropsychiatric diseases, such as schizophrenia, substance use disorders, and stress-related disorders.

Increased Voluntary Alcohol Consumption in Mice Lacking GABAB(1) Is Associated With Functional Changes in Hippocampal GABAA Receptors

Gamma-aminobutyric acid type B receptor (GABA_BR) has been extensively involved in alcohol use disorders; however, the mechanisms by which this receptor modulates alcohol drinking behavior remain murky. In this study, we investigate alcohol consumption and preference in mice lacking functional GABA_BR using the 2-bottle choice paradigm. We found that GABA_B(1), knockout (KO), and heterozygous (HZ) mice drank higher amounts of an alcoholic solution, preferred alcohol to water, and reached higher blood alcohol concentrations (BACs) compared to wild-type (WT) littermates. The GABA_BR agonist GHB significantly reduced alcohol consumption in the GABA_B(1) HZ and WT but not in the KO mice. Next, because of a functional crosstalk between GABA_BR and δ-containing GABA_A receptor (δ-GABA_AR), we profiled δ subunit mRNA expression levels in brain regions in which the crosstalk was characterized. We found a loss of the alcohol-sensitive GABA_AR δ subunit in the hippocampus of the GABA_B(1) KO alcohol-naïve mice that was associated with increased ɣ² subunit abundance. Electrophysiological recordings revealed that these molecular changes were associated with increased phasic inhibition, suggesting a potential gain of synaptic GABA_AR responsiveness to alcohol that has been previously described in an animal model of excessive alcohol drinking. Interestingly, voluntary alcohol consumption did not revert the dramatic loss of hippocampal δ-GABA_AR occurring in the GABA_B(1) KO mice but rather exacerbated this condition. Finally, we profiled hippocampal neuroactive steroids levels following acute alcohols administration in the GABA_B(1) KO and WT mice because of previous involvement of GABA_BR in the regulation of cerebral levels of these compounds. We found that systemic administration of alcohol (1.5 g/kg) did not produce alcohol-induced neurosteroid response in the GABA_B(1) KO mice but elicited an expected increase in the hippocampal level of progesterone and 3α,5α-THP in the WT controls. In conclusion, we show that genetic ablation of the GABA_B(1) subunit results in increased alcohol consumption and preference that were associated with functional changes in hippocampal GABA_AR, suggesting a potential mechanism by which preference for alcohol consumption is maintained in the GABA_B(1) KO mice. In addition, we documented that GABA_B(1) deficiency results in lack of alcohol-induced neurosteroids, and we discussed the potential implications of this finding in the context of alcohol drinking and dependence.

Dopamine-induced changes to thalamic GABA concentration in impulsive Parkinson disease patients

Impulsivity is inherent to behavioral disorders such as substance abuse and binge eating. While the role of dopamine in impulse behavior is well established, γ-aminobutyric acid (GABA) therapies have promise for the treatment of maladaptive behaviors. In Parkinson disease (PD), dopaminergic therapies can result in the development of impulsive and compulsive behaviors, and this clinical syndrome shares similar pathophysiology to that seen in addiction, substance abuse, and binge-eating disorders. We hypothesized that impulsive PD patients have a reduced thalamic GABAergic response to dopamine therapy. To test this hypothesis, we employed GABA magnetic resonance spectroscopy, D2-like receptor PET imaging, and clinical and quantitative measures of impulsivity in PD patients (n = 33), before and after dopamine agonist administration. We find a blunted thalamic GABA response to dopamine agonists in patients with elevated impulsivity (p = 0.027). These results emphasize how dopamine treatment differentially augments thalamic GABA concentrations, which may modify behavioral impulsivity.

Sex differences in GABAA receptor subunit transcript expression are mediated by genotype in subjects with alcohol-related cirrhosis of the liver

Male and female human subjects show contrasting propensities to misuse drugs of addiction, including alcohol. These differences lead to different psychological and neurological consequences, such as the likelihood of developing dependence. The pattern and extent of brain damage in alcohol-use disorder cases also varies with comorbid disease. To explore mechanisms that might underlie these outcomes, we used autopsy tissue to determine mRNA transcript expression in relation to genotype for two GABAA receptor subunit genes. We used quantitative Real-Time PCR to measure GABRA6 and GABRA2 mRNA concentrations in dorsolateral prefrontal and primary motor cortices of alcohol-use disorder subjects and controls of both sexes with and without liver disease who had been genotyped for these GABAA receptor subunit genes. Cirrhotic alcohol-use disorder cases had significantly higher expression of GABRA6 and GABRA2 transcripts than either controls or non-cirrhotic alcohol-use disorder cases. Differences were observed between sexes, genotypes and brain regions. We show that sex differences in subjects with GABRA6 and GABRA2 variants may contribute to differences in susceptibility to alcohol-use disorder and alcohol-induced cirrhosis.

Biomaterial Cues Regulated Differentiation of Neural Stem Cells into GABAergic Neurons through Ca2+/c-Jun/TLX3 Signaling Promoted by Hydroxyapatite Nanorods

Directed differentiation enables the production of a specific cell type by manipulating signals in development. However, there is a lack of effective means to accelerate the regeneration of neurons of particular subtypes for pathogenesis and clinical therapy. In this study, we find that hydroxyapatite (HAp) nanorods promote neural differentiation of neural stem cells due to their chemical compositions. Lysosome-mediated degradation of HAp nanorods elevates intracellular calcium concentrations and accelerates GABAergic neurogenesis. As a mechanism, the enhanced activity of a Ca²⁺ peak initiated by HAp nanorods leads to the activation of c-Jun and thus suppresses the expression of GABAergic/glutamatergic selection gene TLX3. We demonstrate the capability of HAp nanorods in promoting the differentiation into GABAergic neurons at both molecular and cellular function levels. Given that GABAergic neurons are responsible for various physiological and pathological processes, our findings open up enormous opportunities in efficient and precise stem cell therapy of neurodegenerative diseases.

Drug addiction: from bench to bedside

Drug addiction is responsible for millions of deaths per year around the world. Still, its management as a chronic disease is shadowed by misconceptions from the general public. Indeed, drug consumers are often labelled as "weak", "immoral" or "depraved". Consequently, drug addiction is often perceived as an individual problem and not societal. In technical terms, drug addiction is defined as a chronic, relapsing disease resulting from sustained effects of drugs on the brain. Through a better characterisation of the cerebral circuits involved, and the long-term modifications of the brain induced by addictive drugs administrations, first, we might be able to change the way the general public see the patient who is suffering from drug addiction, and second, we might be able to find new treatments to normalise the altered brain homeostasis. In this review, we synthetise the contribution of fundamental research to the understanding drug addiction and its contribution to potential novel therapeutics. Mostly based on drug-induced modifications of synaptic plasticity and epigenetic mechanisms (and their behavioural correlates) and after demonstration of their reversibility, we tried to highlight promising therapeutics. We also underline the specific temporal dynamics and psychosocial aspects of this complex psychiatric disease adding parameters to be considered in clinical trials and paving the way to test new therapeutic venues.

Electrophysiology of ionotropic GABA receptors

GABA_A receptors are ligand-gated chloride channels and ionotropic receptors of GABA, the main inhibitory neurotransmitter in vertebrates. In this review, we discuss the major and diverse roles GABA_A receptors play in the regulation of neuronal communication and the functioning of the brain. GABA_A receptors have complex electrophysiological properties that enable them to mediate different types of currents such as phasic and tonic inhibitory currents. Their activity is finely regulated by membrane voltage, phosphorylation and several ions. GABA_A receptors are pentameric and are assembled from a diverse set of subunits. They are subdivided into numerous subtypes, which differ widely in expression patterns, distribution and electrical activity. Substantial variations in macroscopic neural behavior can emerge from minor differences in structure and molecular activity between subtypes. Therefore, the diversity of GABA_A receptors widens the neuronal repertoire of responses to external signals and contributes to shaping the electrical activity of neurons and other cell types.

Association between GABA receptor delta subunit gene polymorphisms and heroin addiction

Evidence suggests that γ-aminobutyric acid (GABA) receptors are involved in the development of drug dependence. Considering its exclusively extrasynaptic localization, GABA receptor delta subunit (GABRD) is likely involved in heroin addiction. The purpose of this study was to explore the association between the single nucleotide polymorphisms (SNPs) of GABRD and heroin addiction. Genotyping of five SNPs (rs13303344, rs4481796, rs2376805, rs2229110, and rs41307846) in GABRD gene was performed by using TaqMan SNP assay. The association between heroin addiction and these SNPs was assessed in 446 heroin dependent patients and 400 normal control subjects of male Han Chinese origin. Only the genotype and allele frequencies at rs13303344 differed significantly between the cases and controls (nominal P values were 0.028 and 0.019, respectively). The C allele of rs13303344 was associated with an increased risk of heroin addiction (OR = 1.281, 95 % CI: 1.042-1.575). After Bonferroni correction, the association lost significance. The frequencies of the haplotype C-C-A and A-C-A at GARBD (rs13303344-rs4481796- rs2376805) differed significantly between the cases and controls. The heroin craving score was significantly higher in patients with CC/AC genotypes at rs13303344 than in those with the AA genotype (nominal P = 0.017). The results suggest that GABRD rs13303344 may contribute to the susceptibility to heroin addiction and is associated with the drug cravings of heroin dependent patients.

Noninvasive brain stimulation in alcohol craving: A systematic review and meta-analysis

BACKGROUND

Alcohol dependence (AD) is characterized by a set of physical and behavioral symptoms, which may include withdrawal, tolerance and craving. Recently, noninvasive brain stimulation (NIBS) methods, namely transcranial direct current stimulation (tDCS) and transcranial magnetic stimulation (TMS), have been investigated as possible new therapeutic approaches for adjusting the pathological neuroplasticity involved in alcohol dependence. Therefore, we conducted a systematic review and meta-analysis on the therapeutic uses of tDCS and rTMS in AD patients.

METHODS

A systematic search was performed on Scopus, Web of Science, PubMed, Cochrane library and ProQuest. Search terms presented the diagnoses of interest (alcohol dependence, alcohol craving, alcohol use disorders and hazardous drinkers) and the intervention of interest (NIBS, TMS, rTMS, TBS, tDCS, tACS and transcranial). Original articles reporting the use of tDCS or rTMS to treat AD were screened and studied by two researchers independently based on PRISMA guidelines. Next, in the meta-analysis step, random-effects model was utilized to measure the pooled effect size.

RESULTS

We found 34 eligible studies including 11 tDCS trials and 23 rTMS trials. Three of these studies were case-reports, four were open label trials and the remaining 27 were controlled trials which assessed tDCS/rTMS effects on the three cognitive, behavioral and biological dimensions in AD. The pooled standardized mean differences for the effects of tDCS and rTMS on alcohol cravings were - 0.13 [-0.34, 0.08] and - 0.43 [-1.02, 0.17], respectively.

CONCLUSION

There is no evidence for a positive effect of tDCS/rTMS on various dimensions of AD. We need more randomized, double blind, sham controlled trials with enough follow-up periods to evaluate the efficacy of tDCS/rTMS for alcohol dependence treatment.

Roux-en-Y gastric bypass increases GABA-A receptor levels in regions of the rat brain involved in object recognition memory and perceptual acuity

Roux-en-Y gastric bypass surgery (RYGB), one of the most common and successful procedures for combatting obesity, is associated with post-surgery substance use disorder (SUD) and other addictive behaviors in a subset of patients. We investigated the effects of RYGB on GABA-A receptor levels in the rat brain to identify potential mechanisms of this behavior. The GABAergic system is affected in addiction and has been implicated in the pathology of obesity. We assigned male Sprague-Dawley rats to four groups: standard, low fat diet with sham surgery (control), ad libitum HFD with sham surgery (Sham), calorie restricted HFD with sham surgery (Sham-FR), or HFD with RYGB surgery. Surgery was performed after 8 weeks on the control or HFD diet. Rats maintained their respective diets for 9 weeks post-surgery, then were sacrificed for GABA-A receptor autoradiography using the [³H] Flunitrazepam ligand. We identified increased GABA-A binding in the perirhinal cortex of ad-libitum HFD fed rats compared to normal diet controls. RYGB surgery increased GABA-A in the ectorhinal cortex compared to normal diet controls, and increased binding in the jaw region of the primary somatosensory cortex compared to food-restricted rats that received sham surgery. Hypothalamus GABA-A was also negatively correlated with body weight in the RYGB group, where GABA signaling may play a role in obesity regulation. These results suggest that HFD and RYGB modulate GABA signaling in regions important for object recognition memory, and that increased GABA-A levels in the jaw's perceptual field cortex arise from the surgery itself, independent of caloric restriction.

Efficacy of Gabapentin for the Treatment of Alcohol Use Disorder in Patients With Alcohol Withdrawal Symptoms: A Randomized Clinical Trial

IMPORTANCE

Although an estimated 30 million people meet criteria for alcohol use disorder (AUD), few receive appropriate pharmacotherapy. A more personalized, symptom-specific, approach might improve efficacy and acceptance.

OBJECTIVE

To examine whether gabapentin would be useful in the treatment of AUD, especially in those with the most alcohol withdrawal symptoms.

DESIGN, SETTING, AND PARTICIPANTS

This double-blind randomized clinical trial conducted between November 2014 and June 2018 evaluated gabapentin vs placebo in community-recruited participants screened and treated in an academic outpatient setting over a 16-week treatment period. A total of 145 treatment-seeking individuals who met Diagnostic and Statistical Manual of Mental Disorders (Fifth Edition) criteria for AUD and were not receiving other AUD intervention were screened, and 96 who also met recent alcohol withdrawal criteria were randomized to treatment after 3 abstinent days. Daily drinking was recorded, and percentage of disialo carbohydrate-deficient transferrin in the blood, a heavy drinking marker, was collected at baseline and monthly during treatment.

INTERVENTIONS

Gabapentin up to 1200 mg/d, orally, vs placebo along with 9 medical management visits (20 minutes each).

MAIN OUTCOMES AND MEASURES

The percentage of individuals with no heavy drinking days and those with total abstinence were compared between treatment groups and further evaluated based on prestudy alcohol withdrawal symptoms.

RESULTS

Of 96 randomized individuals, 90 were evaluable (44 in the gabapentin arm and 46 in the placebo arm), with a mean (SD) age of 49.6 (10.1) years; 69 were men (77%) and 85 were white (94%). The evaluable participants had 83% baseline heavy drinking days (4 or more drinks/day for women, 5 or more for men) and met 4.5 alcohol withdrawal criteria from the Diagnostic and Statistical Manual of Mental Disorders (Fifth Edition). More gabapentin-treated individuals had no heavy drinking days (12 of 44 participants [27%]) compared with placebo (4 of 46 participants [9%]), a difference of 18.6% (95% CI, 3.1-34.1; P = .02; number needed to treat [NNT], 5.4), and more total abstinence (8 of 44 [18%]) compared with placebo (2 of 46 [4%]), a difference of 13.8% (95% CI, 1.0-26.7; P = .04; NNT, 6.2). The prestudy high-alcohol withdrawal group had positive gabapentin effects on no heavy drinking days (P < .02; NNT, 3.1) and total abstinence (P = .003; NNT, 2.7) compared with placebo, while within the low-alcohol withdrawal group, there were no significant differences. These findings were similar for other drinking variables, where gabapentin was more efficacious than placebo in the high-alcohol withdrawal group only. Gabapentin caused more dizziness, but this did not affect efficacy.

CONCLUSIONS AND RELEVANCE

These data, combined with others, suggest gabapentin might be most efficacious in people with AUD and a history of alcohol withdrawal symptoms. Future studies should evaluate sleep changes and mood during early recovery as mediators of gabapentin efficacy.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT02349477.

High frequency deep transcranial magnetic stimulation acutely increases β-endorphins in obese humans

PURPOSE

In obesity, metabolic and voluntary factors regulate appetite, and a dysregulation of the reward pathway was demonstrated in all addiction disorders. Deep transcranial magnetic stimulation (dTMS) is already used to modulate cerebral dopamine activation in neuro-psychiatric diseases. We presently assess the acute effect of high frequency (HF) and low frequency (LF) dTMS on the modulation of the main neuropeptides and neurotransmitters involved in the reward pathway in obese subjects.

METHODS

This study was designed as a double-blind, sham-controlled, randomized clinical trial. Thirty-three obese patients (9 males, 24 females, age 48.1 ± 10.6, BMI 36.4 ± 4.7) were enrolled in the study. All patients were studied during a single dTMS session and blood aliquots were drawn before and after a single dTMS session. Metabolic and neuro-endocrine parameters were evaluated before and after: (1) 18 Hz dTMS (HF, 13 patients); (2) 1 Hz dTMS (LF, 10 patients); (3) Sham treatment (Sham, 10 patients).

RESULTS

No statistically significant variations in metabolic parameters, systolic and diastolic blood pressure, and heart rate were shown acutely. HF showed a significant increase of β-endorphin compared to other groups (p = 0.048); a significant increase of ghrelin in LF (p = 0.041) was also demonstrated.

CONCLUSIONS

A single session of HF dTMS treatment determines in obese subjects an acute increase of β-endorphin level, indicating an activation of the reward pathway. The present findings constitute proof of principle for a potential application of this methodology in obesity treatment.

The genetics of smoking in individuals with chronic obstructive pulmonary disease

Background

Smoking is the principal modifiable environmental risk factor for chronic obstructive pulmonary disease (COPD) which affects 300 million people and is the 3rd leading cause of death worldwide. Most of the genetic studies of smoking have relied on self-reported smoking status which is vulnerable to reporting and recall bias. Using data from the Lung Health Study (LHS), we sought to identify genetic variants associated with quantitative smoking and cessation in individuals with mild to moderate COPD.

Methods

The LHS is a longitudinal multicenter study of mild-to-moderate COPD subjects who were all smokers at recruitment. We performed genome-wide association studies (GWASs) for salivary cotinine (n = 4024), exhaled carbon monoxide (eCO) (n = 2854), cigarettes per day (CPD) (n = 2706) and smoking cessation at year 5 follow-up (n = 717 quitters and 2175 smokers). The GWAS analyses were adjusted for age, gender, and genetic principal components.

Results

For cotinine levels, SNPs near UGT2B10 gene achieved genome-wide significance (i.e. P < 5 × 10^− 8) with top SNP rs10023464, P = 1.27 × 10^− 11. For eCO levels, one significant SNP was identified which mapped to the CHRNA3 gene (rs12914385, P = 2.38 × 10^− 8). A borderline region mapping to KCNMA1 gene was associated with smoking cessation (rs207675, P = 5.95 × 10^− 8). Of the identified loci, only the CHRNA3/5 locus showed significant associations with lung function but only in heavy smokers. No regions met genome-wide significance for CPD.

Conclusion

The study demonstrates that using objective measures of smoking such as eCO and/or salivary cotinine can more precisely capture the genetic contribution to multiple aspects of smoking behaviour. The KCNMA1 gene association with smoking cessation may represent a potential therapeutic target and warrants further studies.

Trial registration

The Lung Health Study ClinicalTrials.gov Identifier: NCT00000568. Date of registration: October 28, 1999.

Electronic supplementary material

The online version of this article (10.1186/s12931-018-0762-7) contains supplementary material, which is available to authorized users.

Inhibition of Glyoxalase 1 reduces alcohol self-administration in dependent and nondependent rats

Previous studies showed that the glyoxalase 1 (Glo1) gene modulates anxiety-like behavior, seizure susceptibility, depression-like behavior, and alcohol drinking in the drinking-in-the-dark paradigm in nondependent mice. Administration of the small-molecule GLO1 inhibitor S-bromobenzylglutathione cyclopentyl diester (pBBG) decreased alcohol drinking in nondependent mice, suggesting a possible therapeutic strategy. However, the preclinical therapeutic efficacy of pBBG in animal models of alcohol dependence remains to be demonstrated. We tested the effect of pBBG (7.5 and 25 mg/kg) on operant alcohol self-administration in alcohol-dependent and nondependent rats. Wistar rats were trained to self-administer 10% alcohol (v/v) and made dependent by chronic intermittent passive exposure to alcohol vapor for 5 weeks. Pretreatment with pBBG dose-dependently reduced alcohol self-administration in both nondependent and dependent animals, without affecting water self-administration. pBBG treatment was more effective in dependent rats than in nondependent rats. These data extend previous findings that implicated Glo1 in alcohol drinking in nondependent mice by showing even more profound effects in alcohol-dependent rats. These results suggest that the pharmacological inhibition of GLO1 is a relevant therapeutic target for the treatment of alcohol use disorders.

Both active and sham low-frequency rTMS single sessions over the right DLPFC decrease cue-induced cravings among pathological gamblers seeking treatment: A randomized, double-blind, sham-controlled crossover trial

Background Craving is a core symptom of addictive disorders, such as pathological gambling for example. Over the last decade, several studies have assessed the efficacy of repetitive transcranial magnetic stimulation (rTMS) in the addiction field, which triggers the dorsolateral prefrontal cortex (DLPFC) to decrease craving. The STIMJEU study investigated whether a single session of low-frequency (LF, i.e., 1 Hz) rTMS applied to the right DLPFC reduced cue-induced gambling craving in a sample of treatment-seeking pathological gamblers. Methods Thirty patients received both active and sham rTMS in random order and were blinded to the condition in a within-subject crossover design. Outcome measures included self-reported gambling craving (Visual Analog Scale and Gambling Craving Scale) and physiological measures (heart rate and blood pressure). Results The rTMS sessions were associated with a significant decrease in the gambling urge, regardless of whether the session was active or sham. When controlling cue-induced craving levels, no effects were observed on craving for active rTMS. Overall, rTMS was well-tolerated, and the credibility of the sham procedure was assessed and appeared to be appropriate. Conclusions We failed to demonstrate the specific efficacy of one session of LF rTMS to decrease cue-induced craving in pathological gamblers. A strong placebo-effect and rTMS parameters may partly explain these results. Yet, we are convinced that rTMS remains a promising therapeutic method. Further studies are required to examine its potential effect.

Gut microbiota modulates alcohol withdrawal-induced anxiety in mice

Excessive alcohol consumption remains a major public health problem that affects millions of people worldwide. Accumulative experimental evidence has suggested an important involvement of gut microbiota in the modulation of host's immunological and neurological functions. However, it is previously unknown whether enteric microbiota is implicated in the formation of alcohol withdrawal-induced anxiety. Using a murine model of chronic alcoholism and withdrawal, we examined the impact of alcohol consumption on the possible alterations of gut microbiota as well as alcohol withdrawal-induced anxiety and behavior changes. The 16S rRNA sequencing revealed that alcohol consumption did not alter the abundance of bacteria, but markedly changed the composition of gut microbiota. Moreover, the transplantation of enteric microbes from alcohol-fed mice to normal healthy controls remarkably shaped the composition of gut bacteria, and elicited behavioral signs of alcohol withdrawal-induced anxiety. Using quantitative real-time polymerase chain reaction, we further confirmed that the expression of genes implicated in alcohol addiction, BDNF, CRHR1 and OPRM1, was also altered by transplantation of gut microbes from alcohol-exposed donors. Collectively, our findings suggested a possibility that the alterations of gut microbiota composition might contribute to the development of alcohol withdrawal-induced anxiety, and reveal potentially new etiologies for treating alcohol addiction.

Chronic Alcohol, Intrinsic Excitability, and Potassium Channels: Neuroadaptations and Drinking Behavior

Neural mechanisms underlying alcohol use disorder remain elusive, and this lack of understanding has slowed the development of efficacious treatment strategies for reducing relapse rates and prolonging abstinence. While synaptic adaptations produced by chronic alcohol exposure have been extensively characterized in a variety of brain regions, changes in intrinsic excitability of critical projection neurons are understudied. Accumulating evidence suggests that prolonged alcohol drinking and alcohol dependence produce plasticity of intrinsic excitability as measured by changes in evoked action potential firing and after-hyperpolarization amplitude. In this chapter, we describe functional changes in cell firing of projection neurons after long-term alcohol exposure that occur across species and in multiple brain regions. Adaptations in calcium-activated (K_Ca2), voltage-dependent (K_V7), and G protein-coupled inwardly rectifying (K_ir3 or GIRK) potassium channels that regulate the evoked firing and after-hyperpolarization parallel functional changes in intrinsic excitability induced by chronic alcohol. Moreover, there are strong genetic links between alcohol-related behaviors and genes encoding K_Ca2, K_V7, and GIRK channels, and pharmacologically targeting these channels reduces alcohol consumption and alcohol-related behaviors. Together, these studies demonstrate that chronic alcohol drinking produces adaptations in K_Ca2, K_V7, and GIRK channels leading to impaired regulation of the after-hyperpolarization and aberrant cell firing. Correcting the deficit in the after-hyperpolarization with positive modulators of K_Ca2 and K_V7 channels and altering the GIRK channel binding pocket to block the access of alcohol represent a potentially highly effective pharmacological approach that can restore changes in intrinsic excitability and reduce alcohol consumption in affected individuals.

Online effects of transcranial direct current stimulation on prefrontal metabolites in gambling disorder

Gambling disorder is characterized by persistent maladaptive gambling behaviors and is now considered among substance-related and addictive disorders. There is still unmet therapeutic need for these clinical populations, however recent advances indicate that interventions targeting the Glutamatergic/GABAergic system hold promise in reducing symptoms in substance-related and addictive disorders, including gambling disorder. There is some data indicating that transcranial direct current stimulation may hold clinical benefits in substance use disorders and modulate levels of brain metabolites including glutamate and GABA. The goal of the present work was to test whether this non-invasive neurostimulation method modulates key metabolites in gambling disorder. We conducted a sham-controlled, crossover, randomized study, blinded at two levels in order to characterize the effects of transcranial direct current stimulation over the dorsolateral prefrontal cortex on neural metabolites levels in sixteen patients with gambling disorder. Metabolite levels were measured with magnetic resonance spectroscopy from the right dorsolateral prefrontal cortex and the right striatum during active and sham stimulation. Active as compared to sham stimulation elevated prefrontal GABA levels. There were no significant changes between stimulation conditions in prefrontal glutamate + glutamine and N-acetyl Aspartate, or in striatal metabolite levels. Results also indicated positive correlations between metabolite levels during active, but not sham, stimulation and levels of risk taking, impulsivity and craving. Our findings suggest that transcranial direct current stimulation can modulate GABA levels in patients with gambling disorder which may represent an interesting future therapeutic avenue.

Proteomics and metabolomics analysis of hepatic mitochondrial metabolism in alcohol-preferring and non-preferring rats

Alcohol preference induced tolerance in humans and animals when their bodily functions adapt to compensate for the disruption caused by alcohol consumption. This was thought to be an important component of the genetic predisposition to alcoholism. To investigate the underlying mechanisms of hepatic metabolic tolerance during alcohol preference, the alcohol preferring and alcohol non-preferring rats were used in this study. The liver mitochondria were purified for comparative quantitative proteomics analysis, and the liver metabolite extracts were collected for metabolomics analysis. Our study identified 96 differentially expressed hepatic mitochondrial proteins that associated with alcohol preference, the further gene ontology and protein interaction network analysis suggest a down-regulation of amino acid metabolism and up-regulation of lipid metabolism. We found alcohol preference induced a series of enzymes decreased (e.g. SSADH and GABA-T) and several amino acids increased (e.g. glutamate and aspartate) in rat liver, indicating down-regulations of glutamate degradation occurred during alcohol preference. Most of these changes were due to the genetic differences between alcohol preferring and non-preferring animals. Furthermore, this study would provided new insights to further clarify the mechanisms of hepatic metabolic tolerance during alcohol preference.

SYVN1, an ERAD E3 Ubiquitin Ligase, Is Involved in GABAAα1 Degradation Associated with Methamphetamine-Induced Conditioned Place Preference

Abuse of methamphetamine (METH), a powerful addictive amphetamine-type stimulants (ATS), is becoming a global public health problem. The gamma-aminobutyric acid (GABA)ergic system plays a critical role in METH use disorders. By using rat METH conditioned place preference (CPP) model, we previously demonstrated that METH-associated rewarding memory formation was associated with the reduction of GABA_Aα1 expression in the dorsal straitum (Dstr), however, the underlying mechanism was unclear. In the present study, we found that METH-induced CPP formation was accompanied by a significant increase in the expression of Synovial apoptosis inhibitor 1 (SYVN1), an endoplasmic reticulum (ER)-associated degradation (ERAD) E3 ubiquitin ligase, in the Dstr. The siRNA knockdown of SYVN1 significantly increased GABA_Aα1 protein levels in both primary cultured neurons and rodent Dstr. Inhibition of proteasomal activity by MG132 and Lactacystin significantly increased GABA_Aα1 protein levels. We further found that SYVN1 knockdown increased GABA_Aα1 in the intra-ER, but not in the extra-ER. Accordingly, endoplasmic reticulum stress (ERS)-associated Glucose-regulated protein 78 (GRP78) and C/EBP homologous protein (CHOP) increased. Thus, this study revealed that SYVN1, as the ERAD E3 ubiquitin ligase, was associated with Dstr GABA_Aα1 degradation induced by METH conditioned pairing.

The effect of litter separation on methamphetamine-conditioned place preference in post-partum dams

Methamphetamine (METH) abuse among women has recently increased to levels comparable to those observed in men. Although studies using animal models of addiction have begun to include more female subjects, examination of the effects of drugs of abuse on post-partum females is currently lacking. This is especially important in light of the significant hormonal and neurobiological changes that accompany pregnancy and rearing experiences. Furthermore, stress in a known factor in addiction vulnerability and the post-partum experience in the clinical population can be highly stressful. Here, we utilized the conditioned place preference paradigm to investigate the conditioned rewarding effects of METH either in virgin rats or in dams exposed to brief separation (15 min) or long separation (180 min) from the litter. We found that females in the brief separation group showed significantly greater METH conditioned place preference compared with both the long separation and virgin groups. No differences were found in locomotor activity during the conditioning sessions. These findings suggest that peripartum experience and brief litter separation may enhance the rewarding effects of METH.

A novel non-opioid protocol for medically supervised opioid withdrawal and transition to antagonist treatment

BACKGROUND

The clinical feasibility of a novel non-opioid and benzodiazepine-free protocol was assessed for the treatment of medically supervised opioid withdrawal and transition to subsequent relapse prevention strategies.

METHODS

A retrospective chart review of DSM-IV diagnosed opioid-dependent patients admitted for inpatient medically supervised withdrawal examined 84 subjects (52 males, 32 females) treated with a 4-day protocol of scheduled tizanidine, hydroxyzine, and gabapentin. Subjects also received ancillary medications as needed, and routine counseling. Primary outcomes were completion of medically supervised withdrawal, and initiation of injectable extended release (ER) naltrexone treatment. Secondary outcomes included the length of hospital stay, Clinical Opiate Withdrawal Scale (COWS) scores, and facilitation to substance use disorder treatment intervention. Ancillary medication use and adverse effects were also assessed.

RESULTS

A total of 79 (94%) of subjects completed medically supervised withdrawal. A total of 27 (32%) subjects chose to pursue transition to ER naltrexone, and 24 of the 27 (89%) successfully received the injection prior to hospital discharge. The protocol subjects had a mean length of hospital stay of 3.6 days, and the mean COWS scores was 3.3, 3.4, 2.8, and 2.4 on Day 1, 2, 3, and 4, respectively. Furthermore, 71 (85%) engaged in an inpatient or outpatient substance use disorder (SUD) treatment program following protocol completion.

CONCLUSION

This retrospective chart review suggests the feasibility of a novel protocol for medically supervised opioid withdrawal and transition to relapse prevention strategies, including injectable ER naltrexone. This withdrawal protocol does not utilize opioid agonists or other controlled substances.‬‬‬‬.

Genome-wide meta-analysis identifies a novel susceptibility signal at CACNA2D3 for nicotine dependence

Nicotine dependence (ND) has a reported heritability of 40-70%. Low-coverage whole-genome sequencing was conducted in 1,889 samples from the UCSF Family study. Linear mixed models were used to conduct genome-wide association (GWA) tests of ND in this and five cohorts obtained from the database of Genotypes and Phenotypes. Fixed-effect meta-analysis was carried out separately for European (n = 14,713) and African (n = 3,369) participants, and then in a combined analysis of both ancestral groups. The meta-analysis of African participants identified a significant and novel susceptibility signal (rs56247223; p = 4.11 × 10^-8 ). Data from the Genotype-Tissue Expression (GTEx) study suggested the protective allele is associated with reduced mRNA expression of CACNA2D3 in three human brain tissues (p < 4.94 × 10^-2 ). Sequence data from the UCSF Family study suggested that a rare nonsynonymous variant in this gene conferred increased risk for ND (p = 0.01) providing further support for CACNA2D3 involvement in ND. Suggestive associations were observed in six additional regions in both European and merged populations (p < 5.00 × 10^-6 ). The top variants were found to regulate mRNA expression levels of genes in human brains using GTEx data (p < 0.05): HAX1 and CHRNB2 (rs1760803), ADAMTSL1 (rs17198023), PEX2 (rs12680810), GLIS3 (rs12348139), non-coding RNA for LINC00476 (rs10759883), and GABBR1 (rs56020557 and rs62392942). A gene-based association test further supported the relation between GABBR1 and ND (p = 6.36 × 10^-7 ). These findings will inform the biological mechanisms and development of therapeutic targets for ND.

Deep Transcranial Magnetic Stimulation of the Dorsolateral Prefrontal Cortex in Alcohol Use Disorder Patients: Effects on Dopamine Transporter Availability and Alcohol Intake

Repetitive Transcranial Magnetic Stimulation (rTMS) of the dorsolateral prefrontal cortex may affect neuro-adaptations associated with alcohol use disorder (AUD), potentially influencing craving and alcohol intake. We investigated alcohol intake and dopamine transporter (DAT) availability by Single Photon Emission Computed Tomography (SPECT) in the striatum of AUD patients before and after deep rTMS. Fourteen patients underwent baseline clinical and SPECT assessment. Eleven out of fourteen patients were randomized into two groups for the REAL (n.5) or SHAM (n.6) treatment. Clinical and SPECT evaluations were then carried out after four weeks of rTMS sessions (T1). At baseline, AUD patients showed higher striatal DAT availability than healthy control subjects (HC). Patients receiving the REAL stimulation revealed a reduction in DAT availability at T1, whereas the SHAM-treated group did not. In addition, patients receiving the REAL stimulation had a decrease in alcohol intake. The results of this longitudinal pilot study may suggest a modulatory effect of deep rTMS on dopaminergic terminals and a potential clinical efficacy in reducing alcohol intake in AUD patients. Further investigations are required to confirm these preliminary data.

Cortical inhibition within motor and frontal regions in alcohol dependence post-detoxification: A pilot TMS-EEG study

OBJECTIVES

Preclinical studies suggest that cortical alterations within the prefrontal cortex (PFC) are critical to the pathophysiology of alcohol dependence. Combined transcranial magnetic stimulation (TMS) and electroencephalography (EEG) allows direct assessment of cortical excitability and inhibition within the PFC of human subjects. We report the first application of TMS-EEG to measure these indices within the PFC of alcohol-dependent (ALD) patients post-detoxification.

METHODS

Cortical inhibition was assessed in 12 ALD patients and 14 healthy controls through single and paired-pulse TMS paradigms. Long-interval cortical inhibition indexed cortical inhibition in the PFC. In the motor cortex (MC), short- interval intracortical inhibition and cortical silent period determined inhibition, while intracortical facilitation measured facilitation, resting and active motor threshold indexed cortical excitability.

RESULTS

ALD patients demonstrated altered cortical inhibition across the bilateral frontal cortices relative to controls. There was evidence of altered cortical excitability in ALD patients; however, no significant differences in MC inhibition.

CONCLUSIONS

Our study provides first direct evidence of reduced cortical inhibition in the PFC of ALD patients post-detoxification. Altered cortical excitability in the MC may reflect hyper-excitability within the cortex associated with chronic alcohol consumption. These findings provide initial neurophysiological evidence of disrupted cortical excitability within the PFC of ALD patients.

Bilateral Transcranial Magnetic Stimulation of the Prefrontal Cortex Reduces Cocaine Intake: A Pilot Study

BACKGROUND

Chronic cocaine consumption is associated with a decrease in mesolimbic dopamine transmission that maintains drug intake. transcranial magnetic stimulation (TMS) is gaining reliability, a useful therapeutic tool in drug addiction, since it can modulate cortico-limbic activity resulting in reduction of drug craving.

AIMS

In the present study, we investigated the therapeutic effect of bilateral TMS of prefrontal cortex (PFC) in reducing cocaine intake, in a sample of treatment-seeking patients with current cocaine use disorder (DSM-V).

METHODS

Ten cocaine addicts (DSM-V) were randomly assigned to the active or sham stimulation protocol in a double-blind experimental design. Twelve repetitive TMS (rTMS) sessions were administered three times a week for 4 weeks at 100% of motor threshold, over bilateral PFC. Cocaine intake (ng/mg) was assessed by hair analysis at baseline (before treatment, T0), after 1 month (end of treatment, T1), 3 (T2), and 6 (T3) months later. All subjects received psychological support weekly.

RESULTS

The two-way ANOVA for repeated measures did not show a significant effect of the interaction between time and treatment (F 4,32 = 0.35; p = 0.87). Despite that result indicated no difference in the effect of the two conditions (active vs. sham) along time, a decreasing trend in cocaine consumption in active TMS group (F 3,23 = 3.42; p = 0.04) vs. sham (F 3,15 = 1.88; p = 0.20) was observed when we performed exploratory analysis with time as factor. Indeed, Post hoc comparisons showed a significant reduction in the amount of cocaine detected from the onset to 3 months later (T0-T2; p = 0.02) and to the end of treatment (T0-T3; p = 0.01) in addicts from the active group.

CONCLUSION

Bilateral rTMS of PFC at 10 Hz did not show a significant effect on cocaine intake compared to sham. However, a long-term reduction on cocaine intake in active TMS-treated patients was observed when we considered the time as factor. Further studies are required to confirm these encouraging but preliminary findings, in order to consolidate rTMS as a valid tool to treat cocaine addiction.

Long-Term Effects of Repeated Prefrontal Cortex Transcranial Direct Current Stimulation (tDCS) on Food Craving in Normal and Overweight Young Adults

BACKGROUND

The dorsolateral prefrontal cortex (DLPFC) plays an important role in the regulation of food intake. Several previous studies demonstrated that a single session of transcranial direct current stimulation (tDCS) of the DLPFC reduces food craving and caloric intake.

OBJECTIVES

We hypothesized that repeated tDCS of the right DLPFC cortex may exert long-term changes in food craving in young, healthy adults and that these changes may differ between normal and overweight subjects.

METHODS

Thirty healthy individuals who reported frequent food cravings without a prior history of eating disorders were initially recruited. Subjects were randomized into an ACTIVE group who received 5 days of real tDCS (20 minutes, anode right-cathode left montage, 2 mA with current density kept at 0.06 mA/cm2, 1 min ramp-up/ramp-down), and a SHAM group, who received one day of real tDCS, on the first day (same parameters), followed by 4 days of sham tDCS. Food craving intensity was examined by Food Craving Questionnaires State and Trait and Food Craving Inventory before, during, (5-days) and one month (30-days) after tDCS.

RESULTS

Single session of tDCS significantly reduced the intensity of current food craving (FCQ-S). Five days of active tDCS significantly reduced habitual experiences of food craving (FCQ-T), when compared to baseline pre-stimulation levels. Furthermore, both current (FCQ-S) and habitual craving (FCQ-T) were significantly reduced 30 days after active tDCS, while sham tDCS, i.e. a single tDCS session did not have significant effects. Also, active tDCS significantly decreased craving for fast food and sweets, and to a lesser degree for fat, while it did not have significant effects on craving for carbohydrates (FCI). There were no significant differences between individual FCQ-T subscales (craving dimensions) after 5 or 30 days of either sham or active tDCS. Changes in craving were not significantly associated with the initial weight, or with weight changes 30 days after the stimulation in the subjects.

CONCLUSIONS

The results confirm earlier findings that single session of tDCS has immediate effects in reducing food craving. They also show that repeated tDCS over the right DLPFC may increase the duration of its effects, which may be present 30 days after the stimulation. These results support further investigation of the use of tDCS in obesity.

Potentiation of Gamma Aminobutyric Acid Receptors (GABAAR) by Ethanol: How Are Inhibitory Receptors Affected?

In recent years there has been an increase in the understanding of ethanol actions on the type A γ-aminobutyric acid chloride channel (GABA_AR), a member of the pentameric ligand gated ion channels (pLGICs). However, the mechanism by which ethanol potentiates the complex is still not fully understood and a number of publications have shown contradictory results. Thus many questions still remain unresolved requiring further studies for a better comprehension of this effect. The present review concentrates on the involvement of GABA_AR in the acute actions of ethanol and specifically focuses on the immediate, direct or indirect, synaptic and extra-synaptic modulatory effects. To elaborate on the immediate, direct modulation of GABA_AR by acute ethanol exposure, electrophysiological studies investigating the importance of different subunits, and data from receptor mutants will be examined. We will also discuss the nature of the putative binding sites for ethanol based on structural data obtained from other members of the pLGICs family. Finally, we will briefly highlight the glycine gated chloride channel (GlyR), another member of the pLGIC family, as a suitable target for the development of new pharmacological tools.

Alcohol Effects on Stress Pathways: Impact on Craving and Relapse Risk

A significant amount of neurobiological research regarding the development of alcohol use disorders (AUDs) has focused on alcohol-related activation and long-term alterations in the mesocortical dopaminergic reward pathways. However, alcohol does not only interact with brain reward systems. Many of its acute and chronic effects may be related to allostatic adaptations in hypothalamic and extrahypothalamic stress regulation pathways. For example, acute binge intoxication is associated with hypothalamically driven increases in blood cortisol, norepinephrine, and sex steroid metabolite levels. This may contribute to the development of mesocortical sensitization to alcohol. Furthermore, chronic alcohol exposure is associated with systemic dysregulation of the hypothalamic pituitary adrenal axis, sympathetic adrenal medullary system, and sex steroid systems. This dysregulation appears to manifest as neuroendocrine tolerance. In this review, we first summarize the literature suggesting that alcohol-induced alterations in these hypothalamic systems influence craving and contribute to the development of AUDs. We note that for women, the effects of alcohol on these neuroendocrine stress regulation systems may be influenced by the rhythmic variations of hormones and steroids across the menstrual cycle. Second, we discuss how changes in these systems may indicate progression of AUDs and increased risk of relapse in both sexes. Specifically, neuroendocrine tolerance may contribute to mesocortical sensitization, which in turn may lead to decreased prefrontal inhibitory control of the dopaminergic reward and hypothalamic stress systems. Thus, pharmacological strategies that counteract alcohol-associated changes in hypothalamic and extrahypothalamic stress regulation pathways may slow the development and progression of AUDs.

Involvement of dorsal striatal α1-containing GABAA receptors in methamphetamine-associated rewarding memories

Rewarding memories induced by addictive drugs may contribute to persistent drug-seeking behaviors, which is an important contributing factor to drug addiction. However, the biological mechanisms underlying drug-associated rewarding memories have not yet been fully understood, especially the new synthetic drugs, such as amphetamine-type stimulants (ATS). In this study, using the rat-conditioned place preference (CPP) model, a classic animal model for the reward-associated effects of addictive drugs, we found that the expression level of GABAA α1 subunits was significantly decreased in the dorsal striatum (Dstr) after conditioned methamphetamine (METH) pairing, and no significant differences were observed in the other four rewarding memory-associated areas (medial prefrontal cortex (mPFC), nucleus accumbens (NAc), amygdala (Amy), and dorsal hippocampus (DH)). Intra-Dstr injection of either the GABAA receptor agonist muscimol or the specific α1GABAA receptor-preferring benzodiazepine (BDZ) agonist zolpidem significantly abolished METH CPP formation. Thus, this study extends previous findings by showing that GABAA receptors, particularly the α1-containing GABAA receptors, may be strongly implicated in METH-associated rewarding memories. This work provides us with a new perspective on the goal of treating ATS addiction.

Glutamatergic and GABAergic susceptibility loci for heroin and cocaine addiction in subjects of African and European ancestry

BACKGROUND

Drug addiction, a leading health problem, is a chronic brain disease with a significant genetic component. Animal models and clinical studies established the involvement of glutamate and GABA neurotransmission in drug addiction. This study was designed to assess if 258 variants in 27 genes of these systems contribute to the vulnerability to develop drug addiction.

METHODS

Four independent analyses were conducted in a sample of 1860 subjects divided according to drug of abuse (heroin or cocaine) and ancestry (African and European).

RESULTS

A total of 11 SNPs in eight genes showed nominally significant associations (P<0.01) with heroin and/or cocaine addiction in one or both ancestral groups but the associations did not survive correction for multiple testing. Of these SNPs, the GAD1 upstream SNP rs1978340 is potentially functional as it was shown to affect GABA concentrations in the cingulate cortex. In addition, SNPs GABRB3 rs7165224; DBI rs12613135; GAD1 SNPs rs2058725, rs1978340, rs2241164; and GRIN2A rs1650420 were previously reported in associations with drug addiction or related phenotypes.

CONCLUSIONS

The study supports the involvement of genetic variation in the glutamatergic and GABAergic systems in drug addiction with partial overlap in susceptibility loci between cocaine and heroin addiction.

Opioid antagonists block acetaldehyde-induced increments in dopamine neurons activity

BACKGROUND

Acetaldehyde is the main metabolite of ethanol ingested through alcoholic beverages. Traditionally considered aversive is presently being viewed as an activating agent of the mesolimbic dopamine system but underlying mechanisms are only partially known.

METHODS

Through in vivo electrophysiology experiments in rats we have studied the role of endogenous opioids in acetaldehyde-induced increments in dopamine activity.

RESULTS

Here we show that acetaldehyde-induced increase in firing rate, burst firing and spikes/burst of antidromically-identified ventro-tegmental area nucleus accumbens-projecting neurons are abolished by pretreatment with the opiate unselective antagonist naltrexone (0.4 mg/kg/ip). Similar effects are obtained after administration of naloxone (0.1 mg/kg/iv). These results indicate that endogenous opiate system(s) participate in acetaldehyde-induced increments in dopaminergic neuronal activity.

CONCLUSION

These data may explain the reduction in acetaldehyde-induced dopamine release in the nucleus accumbens after blockade of opiate receptors. Considering the paucity of efficacious therapies in alcoholism, and recent developments in ethanol-derived acetaldehyde effects, further experiments are warranted to further elucidate its role as a biomarker potentially useful to develop new strategies in the search for effective compounds aimed at reducing excessive alcohol intake, abuse and ultimately alcoholism.

Serotonin stimulates lateral habenula via activation of the post-synaptic serotonin 2/3 receptors and transient receptor potential channels

There is growing interest on the role of the lateral habenula (LHb) in depression, because it closely and bilaterally connects with the serotoninergic raphe nuclei. The LHb sends glutamate efferents to the raphe nuclei, while it receives serotoninergic afferents, and expresses a high density of serotonin (5-HT) receptors. Recent studies suggest that 5-HT receptors exist both in the presynaptic and postsynaptic sites of LHb neurons, and activation of these receptors may have different effects on the activity of LHb neurons. The current study focused on the effect of 5-HT on the postsynaptic membrane. We found that 5-HT initiated a depolarizing inward current (I((5-HTi))) and accelerated spontaneous firing in ∼80% of LHb neurons in rat brain slices. I((5-HTi)) was also induced by the 5-HT uptake blocker citalopram, indicating activity of endogenous 5-HT. I((5-HTi)) was diminished by 5-HT(2/3) receptor antagonists (ritanserin, SB-200646 or ondansetron), and activated by the selective 5-HT(2/3) agonists 1-(3-Chlorophenyl) piperazine hydrochloride or 1-(3-Chlorophenyl) biguanide hydrochloride. Furthermore, I((5-HTi)) was attenuated by 2-Aminoethyl diphenylborinate, a blocker of transient receptor potential channels, and an IP3 receptor inhibitor, indicating the involvement of transient receptor potential channels. These results demonstrate that the reciprocal connection between the LHb and the 5-HT system highlights a key role for 5-HT stimulation of LHb neurons that may be important in the pathogenesis of depression.

Transcranial direct current stimulation (tDCS) in behavioral and food addiction: a systematic review of efficacy, technical, and methodological issues

Objectives: Behavioral addictions (BA) are complex disorders for which pharmacological and psychotherapeutic treatments have shown their limits. Non-invasive brain stimulation, among which transcranial direct current stimulation (tDCS), has opened up new perspectives in addiction treatment. The purpose of this work is to conduct a critical and systematic review of tDCS efficacy, and of technical and methodological considerations in the field of BA.

Methods: A bibliographic search has been conducted on the Medline and ScienceDirect databases until December 2014, based on the following selection criteria: clinical studies on tDCS and BA (namely eating disorders, compulsive buying, Internet addiction, pathological gambling, sexual addiction, sports addiction, video games addiction). Study selection, data analysis, and reporting were conducted according to the PRISMA guidelines.

Results: Out of 402 potential articles, seven studies were selected. So far focusing essentially on abnormal eating, these studies suggest that tDCS (right prefrontal anode/left prefrontal cathode) reduces food craving induced by visual stimuli.

Conclusions: Despite methodological and technical differences between studies, the results are promising. So far, only few studies of tDCS in BA have been conducted. New research is recommended on the use of tDCS in BA, other than eating disorders.

The use of repetitive transcranial magnetic stimulation for modulating craving and addictive behaviours: a critical literature review of efficacy, technical and methodological considerations

OBJECTIVES

Repetitive transcranial magnetic stimulation (rTMS) is a potential therapeutic intervention for the treatment of addiction. This critical review aims to summarise the recent developments with respect to the efficacy of rTMS for all types of addiction and related disorders (including eating disorders), and concentrates on the associated methodological and technical issues.

METHODS

The bibliographic search consisted of a computerised screening of the Medline and ScienceDirect databases up to December 2013. Criteria for inclusion were the target problem was an addiction, a related disorder, or craving; the intervention was performed using rTMS; and the study was a clinical trial.

RESULTS

Of the potential 638 articles, 18 met the criteria for inclusion. Most of these (11 of the 18) supported the efficacy of rTMS, especially in the short term. In most cases, the main assessment criterion was the measurement of craving using a Visual Analogue Scale.

DISCUSSION

The results are discussed with respect to the study limitations and, in particular, the many methodological and technical discrepancies that were identified. Key recommendations are provided.

Behavioral and Genetic Evidence for GIRK Channels in the CNS: Role in Physiology, Pathophysiology, and Drug Addiction

G protein-coupled inwardly rectifying potassium (GIRK) channels are widely expressed throughout the brain and mediate the inhibitory effects of many neurotransmitters. As a result, these channels are important for normal CNS function and have also been implicated in Down syndrome, Parkinson's disease, psychiatric disorders, epilepsy, and drug addiction. Knockout mouse models have provided extensive insight into the significance of GIRK channels under these conditions. This review examines the behavioral and genetic evidence from animal models and genetic association studies in humans linking GIRK channels with CNS disorders. We further explore the possibility that subunit-selective modulators and other advanced research tools will be instrumental in establishing the role of individual GIRK subunits in drug addiction and other relevant CNS diseases and in potentially advancing treatment options for these disorders.

Anticonvulsants for the treatment of alcohol withdrawal syndrome and alcohol use disorders

Alcoholic patients suffer from harmful allostatic neuroplastic changes in the brain causing an acute withdrawal syndrome upon cessation of drinking followed by a protracted abstinence syndrome and an increased risk of relapse to heavy drinking. Benzodiazepines have long been the treatment of choice for detoxifying patients and managing alcohol withdrawal syndrome (AWS). Non-benzodiazepine anticonvulsants (NBACs) are increasingly being used both for alcohol withdrawal management and for ongoing outpatient treatment of alcohol dependence, with the goal of either abstinence or harm reduction. This expert narrative review summarizes the scientific basis and clinical evidence supporting the use of NBACs in treating AWS and for reducing harmful drinking patterns. There is less evidence in support of NBAC therapy for AWS, with few placebo-controlled trials. Carbamazepine and gabapentin appear to be the most promising adjunctive treatments for AWS, and they may be useful as monotherapy in select cases, especially in outpatient settings and for the treatment of mild-to-moderate low-risk patients with the AWS. The body of evidence supporting the use of the NBACs for reducing harmful drinking in the outpatient setting is stronger. Topiramate appears to have a robust effect on reducing harmful drinking in alcoholics. Gabapentin is a potentially efficacious treatment for reducing the risk of relapse to harmful drinking patterns in outpatient management of alcoholism. Gabapentin's ease of use, rapid titration, good tolerability, and efficacy in both the withdrawal and chronic phases of treatment make it particularly appealing. In summary, several NBACs appear to be beneficial in treating AWS and alcohol use disorders.

The use of virtual reality in craving assessment and cue-exposure therapy in substance use disorders

Craving is recognized as an important diagnosis criterion for substance use disorders (SUDs) and a predictive factor of relapse. Various methods to study craving exist; however, suppressing craving to successfully promote abstinence remains an unmet clinical need in SUDs. One reason is that social and environmental contexts recalling drug and alcohol consumption in the everyday life of patients suffering from SUDs often initiate craving and provoke relapse. Current behavioral therapies for SUDs use the cue-exposure approach to suppress salience of social and environmental contexts that may induce craving. They facilitate learning and cognitive reinforcement of new behavior and entrain craving suppression in the presence of cues related to drug and alcohol consumption. Unfortunately, craving often overweighs behavioral training especially in real social and environmental contexts with peer pressure encouraging the use of substance, such as parties and bars. In this perspective, virtual reality (VR) is gaining interest in the development of cue-reactivity paradigms and practices new skills in treatment. VR enhances ecological validity of traditional craving-induction measurement. In this review, we discuss results from (1) studies using VR and alternative virtual agents in the induction of craving and (2) studies combining cue-exposure therapy with VR in the promotion of abstinence from drugs and alcohol use. They used virtual environments, displaying alcohol and drugs to SUD patients. Moreover, some environments included avatars. Hence, some studies have focused on the social interactions that are associated with drug-seeking behaviors and peer pressure. Findings indicate that VR can successfully increase craving. Studies combining cue–exposure therapy with virtual environment, however, reported mitigated success so far.

Sodium oxybate in the treatment of alcohol withdrawal syndrome: a randomized double-blind comparative study versus oxazepam. The GATE 1 trial

BACKGROUND

Benzodiazepines (BDZs) are the gold standard in the treatment of alcohol withdrawal syndrome (AWS). Sodium oxybate (SMO) has been tested as a treatment for AWS with encouraging results. The aim of this phase IV, multicenter, randomized, double-blind, double-dummy study was to evaluate the efficacy of SMO in comparison with oxazepam in the treatment of uncomplicated AWS.

METHODS

Alcohol-dependent outpatients (n = 126) affected by uncomplicated AWS according to the Clinical Institute Withdrawal Assessment for Alcohol-revised (CIWA-Ar) scale were enrolled in the study and randomized in two groups: 61 patients received SMO and 65 patients received oxazepam for 10 days. The primary endpoint was the reduction of symptoms of AWS measured by the change in the total CIWA-Ar score from baseline (day 1) to the end of the study (day 10). This study is registered with ClinicalTrials.gov, number: NCT02090504 RESULTS: A significant decrease of the mean total CIWA-Ar score from baseline to the end of the study was found in both the SMO (p < 0.0001) and the oxazepam group (p < 0.0001), with no significant differences between the two treatments (p = 0.21). Treatment with SMO and oxazepam resulted in a marked decrease in the severity of the mean CIWA subscales, i.e. sweating, tremor, and anxiety, with no significant differences between the two treatments. Both drugs were well tolerated and no severe side effects were reported.

CONCLUSION

SMO is as effective as oxazepam, one of the gold standard BDZs, in the treatment of uncomplicated AWS. Due to its tolerability and absence of significant side effects, SMO may be considered a valid alternative choice in the treatment of AWS.

Drug abuse relapse rates linked to level of education: can we repair hypodopaminergic-induced cognitive decline with nutrient therapy?

It is well known that athletes and other individuals who have suffered painful injuries are at increased risk for all reward deficiency syndrome (RDS) behaviors, including substance use disorder (SUD). Comparing patient demographics and relapse rates in chemical dependence programs is pertinent because demographics may affect outcomes. Increased risk for relapse and lower academic achievement were found to have a significant association in recent outcome data from a holistic treatment center (HTC) located in North Miami Beach, FL. Relapse outcomes from the Drug Addiction Treatment Outcome Study (DATOS; n = 1738) and HTC (n = 224) were compared for a 12-month period. Post-discharge relapse was reported by 26% of HTC patients and 58% of patients in DATOS. When broken out by education level-less than high school, high school diploma, college degree, and graduate degree-HTC patient relapse was 50%, 36%, 33%, and 16%, respectively, and demonstrated an inverse linear association (F = 5.702; P = 0.017). Looking at DATOS patient relapse rates broken down by educational grades/years completed, patients who attended school between 7th grade and 4 years of college also demonstrated an inverse linear association (F = 5.563; P = 0.018). Additionally, the lowest performers, patients who reported their academic performance as "not so good," had the highest relapse (F = 4.226; P = 0.04). Albeit certain limitations, compared with DATOS patients, HTC patients produced significantly larger net differences in relapse rates (X 2 = 84.09; P = 0.0001), suggesting that other variables, such as the treatment model may also affect patient relapse. Our results implicate the use of vitamin and mineral supplements coupled with a well-researched natural dopamine agonist nutrient therapy; both have been shown to improve cognition and behavior, and thus academic achievement. That relapse is highest among addicts who have less education and who report lower grades is a factor that can be useful when considering treatment type and controlled for when comparing treatment outcomes.