The Effects of Anger on Alcohol Demand and Subjective Alcohol Craving.

BACKGROUND: Anger and anger-related traits have been related to alcohol use in both cross-sectional and prospective studies. However, only a small number of studies have experimentally manipulated anger to examine whether the manipulation of anger influences alcohol craving or the relative reinforcing value of alcohol. METHODS: Participants (N = 231) recruited through Amazon's MTurk were randomly assigned to a provocation condition or a neutral condition prior to completing both the Alcohol Purchase Task and a self-report measure of alcohol craving. Linear regression analyses were conducted to examine the effects of the anger induction, trait hostility, frequency of alcohol use in the past month, and relevant demographic characteristics (gender, age, income) on alcohol craving and indices of alcohol demand. RESULTS: Participants assigned to the provocation condition had greater PMax (B = 0.17, p = 0.012) and breakpoint (B = 0.18, p = 0.006) values, less elastic demand (B = -0.15, p = 0.020), and lower drinking intensity (B = -0.14, p = 0.025) than participants assigned to the neutral condition. Trait hostility was positively related to OMax (B = 0.22, p = 0.001), intensity of demand (B = 0.27, p < 0.001), and subjective alcohol craving posttask (B = 0.32, p < 0.001), but did not moderate the relationship between condition and outcomes. CONCLUSIONS: Although most persistence indices of alcohol demand were sensitive to the anger induction, we did not observe higher scores on amplitude indices or subjective craving in the provocation condition relative to the neutral condition. Further investigation into the role which anger plays in alcohol use is warranted.

Food reinforcement and delay discounting in zBMI-discordant siblings.

OBJECTIVE: The interaction of food reinforcement and the inability to delay gratification are related to adult energy intake and obesity. This study was designed to test the association of sibling pair differences in relative reinforcing efficacy of food and delay discounting on sibling pair differences in zBMI scores of same-gender zBMI-discordant siblings. DESIGN AND METHODS: We tested main and interactive relationships between delay discounting and relative reinforcing efficacy of food on zBMI discordance in 14 zBMI-discordant biological sibling pairs (6 female pairs) using a discordant sibling study design. RESULTS: Sibling pair differences in relative reinforcing efficacy of food were associated with sibling pair differences in zBMI (p= 0.046); this effect was moderated by delay discounting (p <0.002). Sibling pairs with greater differences in relative reinforcing efficacy and delay discounting had greater differences in zBMI. CONCLUSIONS: The combination of greater sibling pair differences in delay discounting and relative reinforcing efficacy is associated with greater discordance in zBMI in adolescent sibling pairs.

Contextual and psychosocial factors influencing drug reward in humans: The importance of non-drug reinforcement.

The reinforcing efficacy, or behavior-strengthening effect, of a substance is a critical determinant of substance use typically quantified by measuring behavioral allocation to the substance under schedules of reinforcement with escalating response requirements. Although responses on these tasks are often used to indicate stable reinforcing effects or trait-level abuse potential for an individual, task designs often demonstrate within-person variability across varying degrees of a constraint within experimental procedures. As a result, quantifying behavioral allocation is an effective approach for measuring the impact of contextual and psychosocial factors on substance reward. We review studies using laboratory self-administration, behavioral economic purchase tasks, and ambulatory assessments to quantify the impact of various contextual and psychosocial factors on behavioral allocation toward consumption of a substance. We selected these assessment approaches because they cover the translational spectrum from experimental control to ecological relevance, with consistent support across these approaches representing greater confidence in the effect. Conceptually, we organized factors that influence substance value into two broad categories: factors that influence the cost/benefit ratio of the substance (social context, stress and affect, cue exposure), and factors that influence the cost/benefit ratio of an alternative (alternative non-drug reinforcers, alternative drug reinforcers, and opportunity costs). We conclude with an overview of future research directions and considerations for clinical application.

Aging reduces the sensitivity to the reinforcing efficacy of morphine.

The US geriatric population is growing and using more opioids than ever before. The purpose of this study was to determine whether aging influenced the reinforcing efficacy of morphine in male and female rats using a rodent intravenous self-administration paradigm. Male and female aged (20-24 months) and young (2-4 months) Wistar rats were tested at 2 doses of morphine (0.75 mg/kg/infusion and 0.25 mg/kg/infusion). During 10 days of self-administration, aged rats took significantly less morphine than their younger counterparts at the 0.25 mg/kg/infusion dose. Aged males also earned significantly fewer infusions on a progressive ration reinforcement schedule at this dose, suggesting that the reinforcing efficacy of morphine is decreased for this group at this dose. These effects dissipated when a separate group of animals had access to the 0.75 mg/kg/infusion dose for both sexes. Our results indicate that morphine is less reinforcing at lower doses in aged male, but not female rats. This research has potential clinical implications for the chronic treatments involving opioids in aged individuals.

Effects of the mGluR2/3 receptor agonist LY379268 on the reinforcing strength of cocaine in rhesus monkeys.

RATIONALE: Because chronic cocaine exposure produces profound effects on brain glutamate function, this system has been investigated as a target for novel medications for cocaine use disorder. Studies in animal models have provided encouraging results for drugs that target metabotropic glutamate receptors (mGluR), particularly group II mGluRs which includes mGluR2 and mGluR3 receptors. OBJECTIVE: The present study examined the effects of the mGluR2/3 receptor-selective agonist, (-)-2-oxa-4-aminobicylco hexane-4,6-dicarboxylic acid (LY379268), in male rhesus monkeys self-administering cocaine under two procedures that assess the strength of cocaine as a reinforcer. METHODS AND RESULTS: In four monkeys, acute effects of LY379268 on food and cocaine self-administration were characterized using a multiple 10-response fixed-ratio food, progressive-ratio cocaine schedule of reinforcement. Maximum injections were delivered when the available cocaine dose was 0.01-0.1 mg/kg. When monkeys self-administered 0.03 mg/kg per injection cocaine, LY379268 (0.001-0.56 mg/kg, i.v.), increased cocaine injections and disrupted food-maintained responding. Another group of monkeys (n = 3) responded under a food-cocaine choice procedure in which a dose-effect curve for self-administered cocaine (0.0, 0.003-0.1 mg/kg per injection) was generated daily. Acute LY379268 (0.01-0.1 mg.kg, i.v.) produced a shift in allocation of responding towards cocaine without affecting the total reinforcers delivered. When treatment was extended to 5 consecutive days, tolerance developed to LY379268-induced increases in cocaine choice. CONCLUSIONS: These data from two complimentary nonhuman primate models of cocaine use disorder are consistently negative with respect to the potential of LY379268 as a pharmacotherapy for reducing ongoing cocaine use.

Relative reinforcing efficacy of cigarettes as a predictor of smoking abstinence among treatment-seeking smokers.

RATIONALE: Relative reinforcing efficacy (RRE) is a core feature of behavioral economic theories of addiction. A measure of RRE in smokers is the cigarette purchase task (CPT). Only one previous study has assessed whether CPT indices predict treatment outcomes among smokers with substance use disorders (SUDs) who were not motivated to quit smoking, limiting the generalizability of the results. OBJECTIVES: This study was aimed at exploring demand indices as predictors of smoking abstinence among participants receiving a cognitive behavioral treatment (CBT) combined with contingency management (CM) versus CBT alone. It also sought to validate the CPT as a measure of RRE. METHODS: Participants were 159 (62.3 % women) smokers aged 44.8 (SD 12.6) years randomized to CBT alone or combined with CM. They smoked an average of 21.1 (SD 8.5) cigarettes per day, and their mean score on the Fagerström Test for Nicotine Dependence (FTND) was 5.5 (SD 1.9). Demand indices were generated from a hypothetical CPT assessed at baseline. RESULTS: Smoking levels were high (≥20 cigarettes) at prices of up to €0.10 per cigarette. Elasticity was the only index that predicted smoking abstinence at the end of treatment, but only in the CBT + CM condition. The variance explained by elasticity was 6.8 % in the independent model and 4.6 % in the covariate model. Cigarette demand indices and smoking-related measures were significantly associated. CONCLUSION: This is the first research showing that CPT is a valid measure of CM outcome among treatment-seeking smokers. This study also provides evidence of convergent validity for the CPT.

Predictors of delay discounting among smokers: education level and a Utility Measure of Cigarette Reinforcement Efficacy are better predictors than demographics, smoking characteristics, executive functioning, impulsivity, or time perception.

Ninety-four smokers completed the delay discounting procedure for either hypothetical amounts of money, $10 (money) and $1000 (money) or hypothetical amounts of cigarettes ($10 and $1000 worth of cigarettes). We investigated how variables previously found to be related to rates of delay discounting accounted for the observed results. These variables included the following: demographic information, smoking characteristics, executive function abilities, impulsivity, time perception, and the Utility Measure of Cigarette Reinforcing Efficacy (UMCE). Education level and UMCE were each significantly correlated with 3 out of 4 of the discounting measures. Moreover, the largest effect sizes observed were between these two measures and the four discounting measures. All potential discounting predictors were also investigated using step-wise linear regression with Bayesian Information Criterion (BIC) analysis­these BIC models revealed that education level and UMCE accounted for large portions of the variance. We conclude that education level and UMCE were the most consistent predictors of discounting. This data is discussed within the framework of a widely accepted neuroeconomic model that suggests that two brain systems separately assess two separate facets of decision-making, and the interplay between these two systems determines self-control in smokers. We hypothesize that education level and UMCE may serve as surrogate measures of the functionality of these two systems and that discounting may be a sentinel measure of self-control.

Influence of reinforcer magnitude and nicotine amount on smoking's acute reinforcement enhancing effects.

BACKGROUND: Nicotine's acute effects on enhancing reinforcement from sensory rewards, shown in animal models, appear to occur with smoking in humans. These effects may vary due to reinforcer magnitude and amount of acute smoke intake (dose). METHODS: In a fully within-subjects design, dependent smokers (n=23) participated in 3 sessions. Each session followed overnight abstinence and involved 4 trials to assess responding via progressive ratio (PR 50%) for sensory reinforcement from high, moderate, or low preference music, or no reward (counter-balanced, 30-s/reinforcer). Sessions differed in smoking prior to each trial: 8 puffs on arrival and 2 puffs/trial ("8+2″), 2 puffs/trial only ("0+2″), or no smoking. Puffs were consumed via CReSS (Clinical Research Support System) to control topography, and smoking involved own brand to ensure palatability and increase generalizability of results. RESULTS: Reinforced responding was influenced by main effects of smoking condition (p<.05) and music reward type (p<.001). Compared to no smoking, responding for music was increased after smoking 8+2/trial puffs (p<.005), but not after 0+2/trial puffs. Smoking condition significantly increased reinforced responding only for the high preference music (p=.01), and not for moderate or low preference music, or for no reward. Withdrawal did not differ between the two smoking sessions, ruling out withdrawal relief as an explanation for differential reinforcement enhancement. CONCLUSIONS: Our findings confirm that just one cigarette after abstinence is sufficient for reinforcement enhancing effects and suggest that such enhancement is greater as magnitude of a reward's reinforcing efficacy increases.