Neural markers of genetic vulnerability to drug addiction

Anticipation of monetary reward in amygdala, insula, caudate are predictors of pleasure sensitivity to d-Amphetamine administration

BACKGROUND

Drug addiction and dependence continue as an unresolved source of morbidity and mortality. Two approaches to identifying risk for abuse and addiction are psychopharmacological challenge studies and neuroimaging experiments. The present study combined these two approaches by examining associations between self-reported euphoria or liking after a dose of d-amphetamine and neural-based responses to anticipation of a monetary reward.

METHODS

Healthy young adults (N = 73) aged 19 and 26, without any history of alcohol/substance dependence completed four laboratory sessions in which they received oral d-amphetamine (20 mg) or placebo, and completed drug effect questionnaires. On a separate session they underwent a functional magnetic resonance imaging scan while they completed a monetary incentive delay task. During the task, we recorded neural signal related to anticipation of winning $5 or $1.50 compared to winning no money (WinMoney-WinZero), in reward related regions.

RESULTS

Liking of amphetamine during the drug sessions was related to differences in activation during the WinMoney-WinZero conditions - in the amygdala (positive), insula (negative) and caudate (negative). In posthoc analyses, liking of amphetamine was also positively correlated with activation of the amygdala during anticipation of large rewards and negatively related to activation of the left insula to both small and large anticipated rewards.

CONCLUSIONS

These findings suggest that individual differences in key regions of the reward network are related to rewarding subjective effects of a stimulant drug. To further clarify these relationships, future pharmacofMRI studies could probe the influence of amphetamine at the neural level during reward anticipation.

Developmentally Specific Associations Between CNR1 Genotype and Cannabis Use Across Emerging Adulthood

OBJECTIVE

Previous studies have found preliminary evidence for associations between common single-nucleotide polymorphisms (SNPs) in the cannabinoid receptor gene CNR1 and cannabis use and dependence. The present study examined a set of eight independent SNPs in or near CNR1 in relation to cannabis use measured longitudinally across emerging adulthood.

METHOD

Using latent growth curve modeling of 10 waves of longitudinal data spanning mean ages 18.4-23.8 years in a sample of non-Hispanic White individuals (n = 334), we tested if genotype at each CNR1 SNP was associated with both level and growth of cannabis use over time. Peer group drug use, a known correlate of individual use, was evaluated as a time-varying predictor of cannabis use and as a moderator of the relationship between SNPs and individual use.

RESULTS

After correction for multiple comparisons, one SNP, rs806374, was significantly associated with individual differences in level-but not growth-of cannabis use over time, such that C carriers were more likely to use cannabis more frequently at study onset (around age 18). Peer drug use was a predictor of individual cannabis use that grew in terms of effect size with time, but did not significantly moderate the effect of rs806374 genotype.

CONCLUSIONS

C carriers at rs806374 may be at specific risk for increased odds of use during the transition out of high school (around age 18). Future studies should investigate potential mechanisms at this developmental stage, including individual differences in subjective response, innate tolerance, reinforcement mechanisms, or general liability for substance misuse.

The uncanny return of the race concept

The aim of this Hypothesis and Theory is to question the recently increasing use of the "race" concept in contemporary genetic, psychiatric, neuroscience as well as social studies. We discuss "race" and related terms used to assign individuals to distinct groups and caution that also concepts such as "ethnicity" or "culture" unduly neglect diversity. We suggest that one factor contributing to the dangerous nature of the "race" concept is that it is based on a mixture of traditional stereotypes about "physiognomy", which are deeply imbued by colonial traditions. Furthermore, the social impact of "race classifications" will be critically reflected. We then examine current ways to apply the term "culture" and caution that while originally derived from a fundamentally different background, "culture" is all too often used as a proxy for "race", particularly when referring to the population of a certain national state or wider region. When used in such contexts, suggesting that all inhabitants of a geographical or political unit belong to a certain "culture" tends to ignore diversity and to suggest a homogeneity, which consciously or unconsciously appears to extend into the realm of biological similarities and differences. Finally, we discuss alternative approaches and their respective relevance to biological and cultural studies.

Drug addiction in pregnancy: disease not moral failure

Nurses have demonstrated concern for years about their interactions with pregnant women who abuse drugs. Reports of nurses' concern with substance abuse have been reported in the literature since the 1980s. As with any chronic disease, drug addiction causes physiologic changes, and the pathology that occurs in the brain drives characteristic behaviors. Research suggests that choices that addicts make are driven by pathology rather than by failure of a moral compass. This article reviews the theoretical explanations for addictive behaviors, describes the pathophysiology of drug addiction that is responsible for the predictable symptoms and behaviors exhibited by women who abuse prescription drugs and other opioids, and identifies nursing interventions to impact positive outcomes. Nurses who have a working knowledge of this disease will provide more effective nursing care to the women they encounter and are better prepared to make a difference in the lives of both women and their children.

Genetics and epigenetics of alcohol dependence

Alcohol dependence is a severe and common disorder associated with high morbidity and mortality rates. Genetic as well as environmental factors are known to modulate susceptibility to alcohol dependence. There is a growing body of evidence suggesting that this interaction between the genome and the environment is mediated by epigenetic mechanisms, e.g. DNA methylation at CpG sites. Following an introduction of epigenetic regulation of gene transcription, this review will provide an overview over recent genetic and epigenetic findings in the context of alcohol dependence focusing on human studies. Finally, we will discuss the current limitations of epigenetic studies as well as the implications of genetic and epigenetic findings for the development of better treatment and prevention strategies.

The relationship between rs3779084 in the dopa decarboxylase (DDC) gene and alcohol consumption is mediated by drinking motives in regular smokers

BACKGROUND

Motivational models of alcohol use propose that the motivation to consume alcohol is the final common pathway to its use. Both alcohol consumption and drinking motives are influenced by latent genetic factors that partially overlap. This study investigated whether drinking motives mediate the associations between alcohol consumption and 2 single-nucleotide polymorphisms (SNPs) from genes involved in serotonin (TPH2; rs1386496) and dopamine synthesis (DDC; rs3779084). Based on earlier work showing that enhancement and coping motives were heritable in regular smokers but not in nonregular smokers, we hypothesized these motives would mediate the relationships between alcohol consumption and these SNPs in regular smokers.

METHODS

Drinking motives data were available from 830 young adult female twins (n = 344 regular smokers and n = 486 never/nonregular smokers). We used confirmatory factor analyses to model enhancement, coping, and alcohol consumption factors and to conduct mediation analyses in the regular smoker and never/nonregular smoker groups.

RESULTS

Our hypothesis was partially supported. The relationship between alcohol consumption and rs1386496 was not mediated by drinking motives in either group. However, in the regular smokers, the relationship between alcohol consumption and rs3779084 was mediated by enhancement and coping motives. Carriers of the rs3779084 minor allele who were regular smokers reported more motivation to consume alcohol. Given this pattern of results was absent in the never/nonregular smokers, our results are consistent with a gene × smoking status interaction.

CONCLUSIONS

In regular smokers, variability at the locus marked by rs3779084 in the DDC gene appears to index biologically based individual differences in the motivation to consume alcohol to attain or improve a positive affective state or to relieve a negative one. These results could be because of increased sensitivity to the reinforcing effects of alcohol among minor allele carriers who smoke, which might be due to structural or functional differences in mesorticolimic dopamine "reward" circuitry.

Sex hormone activity in alcohol addiction: integrating organizational and activational effects

There are well-known sex differences in the epidemiology and etiopathology of alcohol dependence. Male gender is a crucial risk factor for the onset of alcohol addiction. A directly modifying role of testosterone in alcohol addiction-related behavior is well established. Sex hormones exert both permanent (organizational) and transient (activational) effects on the human brain. The sensitive period for these effects lasts throughout life. In this article, we present a novel early sex hormone activity model of alcohol addiction. We propose that early exposure to sex hormones triggers structural (organizational) neuroadaptations. These neuroadaptations affect cellular and behavioral responses to adult sex hormones, sensitize the brain's reward system to the reinforcing properties of alcohol and modulate alcohol addictive behavior later in life. This review outlines clinical findings related to the early sex hormone activity model of alcohol addiction (handedness, the second-to-fourth-finger length ratio, and the androgen receptor and aromatase) and includes clinical and preclinical literature regarding the activational effects of sex hormones in alcohol drinking behavior. Furthermore, we discuss the role of the hypothalamic-pituitary-adrenal and -gonadal axes and the opioid system in mediating the relationship between sex hormone activity and alcohol dependence. We conclude that a combination of exposure to sex hormones in utero and during early development contributes to the risk of alcohol addiction later in life. The early sex hormone activity model of alcohol addiction may prove to be a valuable tool in the development of preventive and therapeutic strategies.

Positive and negative effects of alcohol and nicotine and their interactions: a mechanistic review

Nicotine and alcohol are two of the most commonly abused legal substances. Heavy use of one drug can often lead to, or is predictive of, heavy use of the other drug in adolescents and adults. Heavy drinking and smoking alone are of significant health hazard. The combination of the two, however, can result in synergistic adverse effects particularly in incidences of various cancers (e.g., esophagus). Although detrimental consequences of smoking are well established, nicotine by itself might possess positive and even therapeutic potential. Similarly, alcohol at low or moderated doses may confer beneficial health effects. These opposing findings have generated considerable interest in how these drugs act. Here we will briefly review the negative impact of drinking-smoking co-morbidity followed by factors that appear to contribute to the high rate of co-use of alcohol and nicotine. Our main focus will be on what research is telling us about the central actions and interactions of these drugs, and what has been elucidated about the mechanisms of their positive and negative effects. We will conclude by making suggestions for future research in this area.

Pilot study of the application of magnetic bead protein profiling to the study of biomarkers in addiction research

OBJECTIVES

Proteomic technologies based on mass spectrometry are increasingly used as a valuable tool in clinical research allowing high-throughput protein and peptide profiling to be undertaken. Whilst previous research has focussed the application of this novel technology on the study of patients with disorders compared to comparable individuals from the healthy population, this current study seeks to determine the effect of successful treatment for alcoholism on the serum protein profile obtained.

METHODS

Serum samples were collected from patients after initial treatment for alcohol abuse and also 6 months after treatment. The serum samples were prepared for analysis using reverse phase magnetic bead fractionation and the resulting peptides analysed by matrix assisted laser desorption ionisation time-of-flight (MALDI-ToF) mass spectrometry.

RESULTS

Whilst the majority of the peptides detected by this approach exhibited constant levels between the two time points, three peptides were elevated at the 6-month time point compared to the initial sampling.

CONCLUSIONS

Whilst disorders with very clear biological causes (such as cancer) exhibit significantly different peptide profiles, psychiatric disorders such as alcohol addiction which are multifactorial show less obvious changes. Despite this the two groups of samples could statistically be distinguished by certain peptides expression levels.

Health differentials in the older population of England: an empirical comparison of the materialist, lifestyle and psychosocial hypotheses

BACKGROUND

In developed countries with old age structures most deaths occur at older ages and older people account for the majority of those in poor health, which suggests a particular need to investigate health inequalities in the older population.

METHODS

We empirically compared the materialist, psychosocial and lifestyle/behavioural theoretical mechanisms of explanation for socio-economic variation in health using data from two waves of the English Longitudinal Study of Ageing (ELSA), a nationally representative multi-purpose sample of the population aged 50 and over living in England. Three dimensions of health were examined: somatic health, depression and well-being.

RESULTS

The materialist and lifestyle/behavioural paths had the most prominent mediating role in the association between socio-economic position and health in the older population, whereas the psychosocial pathway was less influential and exerted most of its influence on depression and well-being, with part of its effect being due to the availability of material resources.

CONCLUSIONS

From a policy perspective there is therefore an indication that population interventions to reduce health differentials and thus improve the overall health of the older population should focus on material circumstances and population based interventions to promote healthy lifestyles.