Human functional neuroimaging connectivity research in dependence

Functional and effective connectivity are relatively new techniques in the analysis of functional neuroimaging studies in humans. They have previously been used in studies of 'normal' psychological and neurological processes such as vision before gradually transferring into use in pathological disease states such as schizophrenia. These techniques are now beginning to extend into the field of substance misuse and dependence. So far, most functional neuroimaging studies in this field have shown consistent patterns of activation in several brain regions, and theories are emerging based upon these and animal models. Studies of brain connectivity can now begin to help further unravel the tangle of disparate brain regions and their connections that underpin the psychopharmacological processes of dependence

GABA-B receptor function in healthy volunteers, a pharmacokinetic and pharmacodynamic study of two doses of baclofen compared to placebo

AIMS AND HYPOTHESIS To assess the subjective and objective effects of baclofen on brain function in healthy volunteers. BACKGROUND Recent evidence suggests baclofen, a γ-aminobutyric acid type B (GABA-B) receptor agonist, reduces alcohol consumption and craving and promotes abstinence in alcoholics. However, characterisation of the GABA-B receptor system in clinical addiction is limited, and it is unclear why some patients require, or tolerate, higher doses to treat alcoholism. This study assesses the effects of baclofen on brain function in healthy volunteers to inform future studies investigating the sensitivity of GABA-B receptors in alcohol addiction. METHODS Eight healthy male volunteers completed a double blind randomised 3-way cross over study, receiving oral placebo (vitamin C 100mg), 10mg and 60mg baclofen. Subjective and objective measurements were taken at baseline (before medication) and at +30mins, 1, 2, 3, 4 and 6 hours after dosing. Objective measures included blood plasma samples, heart rate and blood pressure. Subjective measures included; the Subjective High Assessment Questionnaire (SHAS), visual analogue scales for sleepy, relaxed, tense and alert and a motor coordination task (zig-zag task). Pharmacokinetic data was obtained using liquid chromatography mass-spectrometry (LC-MS) to measure plasma baclofen concentrations. RESULTS 60mg Baclofen showed changes in subjective measures peaking at 2 hours post dosing compared with placebo, including a significant increase (p<0.05) in total SHAS scores with individual items, including feeling ‘drunk or intoxicated’, effects of alcohol and ‘muddled or confused’ particular affected.. Systolic blood pressure was significantly increased (p<0.05) at the 2 hours post 60mg dose. For both 10mg and 60mg baclofen, peak plasma concentration was achieved 60 minutes post dose. Pharmacokinetic data will be presented. There were no significant changes in these measures between 10mg Baclofen and placebo. CONCLUSIONS The objective and subjective measures used in this study are able to differentiate between placebo and 60mg baclofen. These findings will inform further research investigating the sensitivity of GABA-B receptors in alcohol addiction

Significant reductions in human visual gamma frequency by the gaba reuptake inhibitor tiagabine revealed by robust peak frequency estimation

The frequency of visual gamma oscillations is determined by both the neuronal excitation-inhibition balance and the time constants of GABAergic processes. The gamma peak frequency has been linked to sensory processing, cognitive function, cortical structure, and may have a genetic contribution. To disentangle the intricate relationship among these factors, accurate and reliable estimates of peak frequency are required. Here, a bootstrapping approach that provides estimates of peak frequency reliability, thereby increasing the robustness of the inferences made on this parameter was developed. The method using both simulated data and real data from two previous pharmacological MEG studies of visual gamma with alcohol and tiagabine was validated. In particular, the study by Muthukumaraswamy et al. [] (Neuropsychopharmacology 38(6):1105-1112), in which GABAergic enhancement by tiagabine had previously demonstrated a null effect on visual gamma oscillations, contrasting with strong evidence from both animal models and very recent human studies was re-evaluated. After improved peak frequency estimation and additional exclusion of unreliably measured data, it was found that the GABA reuptake inhibitor tiagabine did produce, as predicted, a marked decrease in visual gamma oscillation frequency. This result demonstrates the potential impact of objective approaches to data quality control, and provides additional translational evidence for the mechanisms of GABAergic transmission generating gamma oscillations in humans. Hum Brain Mapp, 2016. © 2016 Wiley Periodicals, Inc

Ethanol reversal of tolerance to the respiratory depressant effects of morphine

Opioids are the most common drugs associated with unintentional drug overdose. Death results from respiratory depression. Prolonged use of opioids results in the development of tolerance but the degree of tolerance is thought to vary between different effects of the drugs. Many opioid addicts regularly consume alcohol (ethanol), and post-mortem analyses of opioid overdose deaths have revealed an inverse correlation between blood morphine and ethanol levels. In the present study, we determined whether ethanol reduced tolerance to the respiratory depressant effects of opioids. Mice were treated with opioids (morphine, methadone, or buprenorphine) for up to 6 days. Respiration was measured in freely moving animals breathing 5% CO(2) in air in plethysmograph chambers. Antinociception (analgesia) was measured as the latency to remove the tail from a thermal stimulus. Opioid tolerance was assessed by measuring the response to a challenge dose of morphine (10 mg/kg i.p.). Tolerance developed to the respiratory depressant effect of morphine but at a slower rate than tolerance to its antinociceptive effect. A low dose of ethanol (0.3 mg/kg) alone did not depress respiration but in prolonged morphine-treated animals respiratory depression was observed when ethanol was co-administered with the morphine challenge. Ethanol did not alter the brain levels of morphine. In contrast, in methadone- or buprenorphine-treated animals no respiratory depression was observed when ethanol was co-administered along with the morphine challenge. As heroin is converted to morphine in man, selective reversal of morphine tolerance by ethanol may be a contributory factor in heroin overdose deaths

Interdisciplinary working in public health research: a proposed good practice checklist.

Background: Guidance on how different disciplines from the natural, behavioural and social sciences can collaborate to resolve complex public health problems is lacking. This article presents a checklist to support researchers and principle investigators to develop and implement interdisciplinary collaborations. Methods: Fourteen individuals, representing 10 disciplines, participated in in-depth interviews to explore the strengths and challenges of working together on an interdisciplinary project to identify the determinants of substance use and gambling disorders, and to make recommendations for future interdisciplinary teams. Data were analysed thematically and a checklist was derived from insights offered by participants during interview and discussion among the authors on the implications of findings. Results: Participants identified 18 scientific, interactional and structural strengths and challenges of interdisciplinary research. These findings were used to develop an 18-item BASICS checklist to support future interdisciplinary collaborations. The five domains of the checklist are: (i) Blueprint, (ii) Attitudes, (iii) Staffing, (iv) Interactions and (v) Core Science. Conclusion: Interdisciplinary work has the potential to advance public health science but the numerous challenges should not be underestimated. Use of a checklist, such as BASICS, when planning and managing projects may help future collaborations to avoid some of the common pitfalls of interdisciplinary research

Impact of COVID-19 restrictions on alcohol consumption behaviours

Background We aimed to evaluate how coronavirus (COVID-19) restrictions had altered individual's drinking behaviours, including consumption, hangover experiences, and motivations to drink, and changing levels of depression and anxiety. Method We conducted an online cross-sectional self-report survey. Whole group analysis compared pre- versus post-COVID restrictions. A correlation coefficient matrix evaluated the associations between all outcome scores. Self-report data was compared with Alcohol Use Disorders Identification Test (AUDIT) scores from the 2014 Adult Psychiatric Morbidity Survey. Multiple linear modelling (MLM) was calculated to identify factors associated with increasing AUDIT scores and post-restriction AUDIT scores. Results In total, 346 individuals completed the survey, of which 336 reported drinking and were therefore analysed. After COVID-19 restrictions 23.2% of respondents reported an increased AUDIT score, and 60.1% a decreased score. AUDIT score change was positively correlated with change in depression (P < 0.01, r = 0.15), anxiety (P < 0.01, r = 0.15) and drinking to cope scores (P < 0.0001, r = 0.35). MLM revealed that higher AUDIT scores were associated with age, mental illness, lack of a garden, self-employed or furloughed individuals, a confirmed COVID-19 diagnosis and smoking status. Conclusions COVID-19 restrictions decreased alcohol consumption for the majority of individuals in this study. However, a small proportion increased their consumption; this related to drinking to cope and increased depression and anxiety

Validated method for the quantification of baclofen in human plasma using solid-phase extraction and liquid chromatography–tandem mass spectrometry

A highly sensitive and fully validated method was developed for the quantification of baclofen in human plasma. After adjusting the pH of the plasma samples using a phosphate buffer solution (pH 4), baclofen was purified using mixed mode (C8/cation exchange) solid-phase extraction (SPE) cartridges. Endogenous water-soluble compounds and lipids were removed from the cartridges before the samples were eluted and concentrated. The samples were analyzed using triple-quadrupole liquid chromatography–tandem mass spectrometry (LC–MS-MS) with triggered dynamic multiple reaction monitoring mode for simultaneous quantification and confirmation. The assay was linear from 25 to 1,000 ng/mL (r2 > 0.999; n = 6). Intraday (n = 6) and interday (n = 15) imprecisions (% relative standard deviation) were <5%, and the average recovery was 30%. The limit of detection of the method was 5 ng/mL, and the limit of quantification was 25 ng/mL. Plasma samples from healthy male volunteers (n = 9, median age: 22) given two single oral doses of baclofen (10 and 60 mg) on nonconsecutive days were analyzed to demonstrate method applicability

Improving GHB withdrawal with baclofen: study protocol for a feasibility study for a randomised controlled trial

Background: GHB (gamma-hydroxybutyrate) and its pro-drugs GBL (gamma-butyrolactone) and 1,4-butanediol (1,4-BD) are central nervous system depressants whose street names include ‘G’ and ‘liquid ecstasy’. They are used recreationally predominately for their stimulant and pro-sexual effects or for sedation to help with sleep and/or to ‘come down’ after using stimulant recreational drugs. Although overall population prevalence is low (0.1 %), in some groups such as men who have sex with men, GHB/GBL use may reach 20 %. GHB/GBL dependence may be associated with severe withdrawal with individuals presenting either acutely to emergency departments or to addiction services for support. Benzodiazepines are currently prescribed for GHB/GBL detoxification but do not prevent all complications, such as behavioural disinhibition, that may require hospitalisation or admission to a high dependency /intensive care unit. The GABAB receptor mediates most effects of GHB/GBL and the GABAB agonist, baclofen, has shown promise as an adjunct to benzodiazepines in reducing withdrawal severity when prescribed both during withdrawal and as a 2-day ‘preload’ prior to detoxification. The key aim of this feasibility study is provide information about recruitment and characteristics of the proposed outcome measure (symptom severity, complications including delirium and treatment escalation) to inform an application for a definitive randomised placebo controlled trial to determine the role of baclofen in the management of GHB/GBL withdrawal and whether starting baclofen 2 days earlier improves outcomes further. Methods/design: This is a prospective, randomised, double-blind, placebo-controlled feasibility study that will recruit participants (aged over 18 years) who are GHB/GBL- dependent and wish to undergo planned GHB/GBL detoxification or are at risk of acute withdrawal and are inpatients requiring unplanned withdrawal. We aim to recruit 88 participants: 28 unplanned inpatients and 60 planned outpatients. During detoxification we will compare baclofen 10 mg three times a day with placebo as an adjunct to the usual benzodiazepine regimen. In the planned outpatient arm, we will also compare a 2-day preload of baclofen 10 mg three times a day with placebo. Ratings of GHB/GBL withdrawal, sleep, depression, anxiety as well as GHB/GBL use will be collected. The main data analyses will be descriptive about recruitment and characterising the impact of adding baclofen to the usual benzodiazepine regimen on measures and outcomes of GHB/GBL withdrawal to provide estimates of variability and effect size. A qualitative approach will evaluate research participant and clinician acceptability and data collected to inform cost-effectiveness. Discussion: This feasibility study will inform a randomised controlled trial to establish whether adding baclofen to a benzodiazepine regimen reduces the severity and complications of GHB/GBL withdrawal

Nature or nurture? Determining the heritability of human striatal dopamine function:an [18F]-DOPA PET study

Striatal dopamine function is important for normal personality, cognitive processes and behavior, and abnormalities are linked to a number of neuropsychiatric disorders. However, no studies have examined the relative influence of genetic inheritance and environmental factors in determining striatal dopamine function. Using [18F]-DOPA positron emission tomography (PET), we sought to determine the heritability of presynaptic striatal dopamine function by comparing variability in uptake values in same sex monozygotic (MZ) twins to dizygotic (DZ) twins. Nine MZ and 10 DZ twin pairs underwent high-resolution [18F]-DOPA PET to assess presynaptic striatal dopamine function. Uptake values for the overall striatum and functional striatal subdivisions were determined by a Patlak analysis using a cerebellar reference region. Heritability, shared environmental effects and non-shared individual-specific effects were estimated using a region of interest (ROI) analysis and a confirmatory parametric analysis. Overall striatal heritability estimates from the ROI and parametric analyses were 0.44 and 0.33, respectively. We found a distinction between striatal heritability in the functional subdivisions, with the greatest heritability estimates occurring in the sensorimotor striatum and the greatest effect of individual-specific environmental factors in the limbic striatum. Our results indicate that variation in overall presynaptic striatal dopamine function is determined by a combination of genetic factors and individual-specific environmental factors, with familial environmental effects having no effect. These findings underline the importance of individual-specific environmental factors for striatal dopaminergic function, particularly in the limbic striatum, with implications for understanding neuropsychiatric disorders such as schizophrenia and addictions

Using [11C]Ro15 4513 PET to characterise GABA-benzodiazepine receptors in opiate addiction: Similarities and differences with alcoholism

The importance of the GABA-benzodiazepine receptor complex and its subtypes are increasingly recognised in addiction. Using the α1/α5 benzodiazepine receptor PET radioligand [ 23 11C]Ro15 4513, we previously showed reduced binding in the nucleus accumbens and hippocampus in abstinent alcohol dependence. We proposed that 24 reduced [ 25 11C]Ro15 4513 binding in the nucleus accumbens was a marker of addiction whilst the reduction in hippocampus and positive relationship with memory was a consequence of chronic alcohol abuse. To examine this 26 further we assessed [ 27 11C]Ro15 4513 binding in another addiction, opiate dependence, and used spectral analysis to estimate contributions of α1 and α5 subtypes to [ 28 11C]Ro15 4513 binding in opiate and previously acquired alcohol-dependent groups. Opiate substitute maintained opiate-dependent men (n = 12) underwent an [ 29 11C]Ro15 4513 PET scan and compared with matched healthy controls (n = 13). We found a significant reduction in 30 [ 31 11C]Ro15 4513 binding in the nucleus accumbens in the opiate-dependent compared with the healthy control group. There was no relationship between [ 32 11C]Ro15 4513 binding in the hippocampus with memory. We found that reduced [ 33 11C]Ro15 4513 binding was associated with reduced α5 but not α1 subtypes in the opiate-dependent group. This was also seen in an alcohol-dependent group where an association between memory 34 performance and [ 35 11C]Ro15 4513 binding was primarily driven by α5 and not α1 subtype. We suggest that reduced α5 levels in the nucleus accumbens are associated with addiction since we have now shown this in depen- 36 dence to two pharmacologically different substances, alcohol and opiates