Tobacco smoking may delay habituation of reinforcer effectiveness in humans

An Evaluation of Zebrafish, an Emerging Model Analyzing the Effects of Toxicants on Cognitive and Neuromuscular Function

An emerging alternative to conventional animal models in toxicology research is the zebrafish. Their accelerated development, regenerative capacity, transparent physical appearance, ability to be genetically manipulated, and ease of housing and care make them feasible and efficient experimental models. Nonetheless, their most esteemed asset is their 70% (+) genetic similarity with the human genome, which allows the model to be used in a variety of clinically relevant studies. With these attributes, we propose the zebrafish is an excellent model for analyzing cognitive and neuromuscular responses when exposed to toxicants. Neurocognition can be readily analyzed using visual discrimination, memory and learning, and social behavior testing. Neuromuscular function can be analyzed using techniques such as the startle response, assessment of activity level, and evaluation of critical swimming speed. Furthermore, selectively mutated zebrafish is another novel application of this species in behavioral and pharmacological studies, which can be exploited in toxicological studies. There is a critical need in biomedical research to discover ethical and cost-effective methods to develop new products, including drugs. Through mutagenesis, zebrafish models have become key in meeting this need by advancing the field in numerous areas of biomedical research.

Reinforcement enhancement by nicotine: A novel abuse-liability assessment of e-cigarettes in young adults

Nicotine can act as a primary positive reinforcer, and as negative reinforcer to relieve withdrawal; we tested whether it can also enhance the reinforcing efficacy of non-drug reinforcers. Young-adult never-users were delivered nicotine via e-cigarette, and a videogame reinforcer was used to test nicotine enhancement. Three dose groups were tested (placebo-only, 6 or 12-mg nicotine), and participants returned to the lab for several sessions over the course of 1 month. Those in the two nicotine-dose groups received placebo on some occasions and nicotine on others; nicotine enhancement of the videogame reinforcer was assessed in a within-subjects fashion by comparing each of the two nicotine groups' dedicated nicotine dose to placebo. In the placebo-only group, progressive-ratio (PR) schedule breakpoints did not alter as a function of videogame exposure, suggesting that the videogame retained its basic-reinforcing properties throughout the study. For the two groups that received nicotine, both doses of nicotine increased PR-schedule breakpoints for the videogame reinforcer relative to the placebo condition. Although nicotine was associated with greater subjective evaluation of the enjoyment of the videogame, it was unrelated to the enjoyment of the e-cigarette device. No evidence was found that nicotine elevated either anhedonia or withdrawal symptoms in the timeframe of the study. The results provide initial evidence that nicotine enhancement, via electronic cigarettes, occurs in non-frequent users of nicotine products and may be a reason they can develop nicotine dependence in the absence of withdrawal and direct effects of nicotine. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Anhedonia in Nicotine Dependence

Prior findings indicate that trait anhedonia enhances the likelihood of becoming a tobacco smoker, and preliminary evidence suggests that smoking abstinence leads to anhedonic states in some individuals and situations, and nicotine administration reduces anhedonic states. Nevertheless, many vital questions exist concerning relationships between anhedonia and nicotine dependence, including situational and individual difference factors that may moderate the strength of these associations. This chapter provides a critical review of the literature assessing relationships of anhedonia to nicotine dependence and the effects of acute nicotine through the lenses of the Research Domain Criteria's (RDoC) Positive Valence Systems (NIMH, RDoC changes to the matrix (CMAT) workgroup update: proposed positive valence domain revisions. A report by the national advisory mental health council workgroup on changes to the research domain criteria matrix, 2018) and the Situation x Trait Affective Response (STAR) model of nicotine's effects and nicotine dependence (Gilbert, Smoking individual differences, psychopathology, and emotion. Taylor and Francis, Washington, DC, 1995; Gilbert, Hum Psychopharmacol Clin Exp 12:S89-S102, 1997). The effects of nicotine and nicotine withdrawal on subjective, behavioral, and brain indices vary across the three RDoC Positive Valences Systems (Reward Responsiveness, Reward Learning, and Reward Valuation) in a manner that supports the research and potential clinical utility of using RDoC criteria and the STAR model to guide research and clinical innovation. We provide a revision of the STAR model that incorporates the three RDoC Positive Valence Systems with evidence that nicotine's effects on hedonic and affective processes vary as a function of the dominance/salience of (1) situational hedonic and affective cues and task/active coping cues, and (2) state executive functioning level/capacity and state reward sensitivity such that these effects of nicotine are maximal during states of suboptimal cognitive functioning and reward sensitivity, combined with low situational stimulus salience and low task-related cues/demands.

Impact of Graphic Warning Messages on Intentions to Use Alternate Tobacco Products

Graphic cigarette warnings increase quit attempts. Perceived message effectiveness and message avoidance are predictive of later quit attempts. We sought to examine whether randomized exposure to warning messages would inadvertently increase intentions to use alternate tobacco products while enhancing attempts to quit cigarettes. An online survey of 1392 adult smokers in the US asked participants to rate six randomly selected tobacco warnings (from a set of 319) on perceived effectiveness and avoidance intentions. These two indicators of message effectiveness were calculated at the message-level and then at the individual campaign-level to facilitate causal inference. After viewing a message campaign of six warning messages, participants indicated their intentions to use alternate tobacco products. Sixty-eight percent of participants reported some intention to use e-cigarettes and intentions to use other alternate tobacco products ranged from 31% to 40%. Campaigns of messages eliciting higher avoidance increased the odds of intending to use hookah (aOR: 4.32), smokeless tobacco (aOR: 4.88), and snus (aOR: 8.06), but not the intention to use electronic cigarettes. These relationships are mediated by intentions to quit smoking (all p <.05). Viewing campaigns with higher campaign-level perceived effectiveness increased the intentions to quit, which in turn increased intentions to try alternate tobacco products. Our findings increase the tobacco control community's understanding of unintended consequences of graphic tobacco warnings.

Preliminary Evaluations of Habituation of Operant Responding for Sensory Stimuli in Humans

Research suggests that repetitive reinforcers wane in their ability to maintain operant behavior in a manner consistent with habituation. Weaker reinforcers, including sensory stimuli common in human work, may be most impacted by repetition. The present research examined within-session operant responding patterns for visual stimuli in humans from two experiments assessing multiple characteristics of habituation. In Experiment 1, declines in reinforced responding were assessed and stimulus specificity was evaluated to test habituation's contribution to these declines. Seventy-three participants completed two visits, both including a reinforcement paradigm using pictures. With repetition, operant responding declined. The stimulus specificity manipulation did not enhance responding, suggesting that habituation did not contribute to response declines. Several methodological concerns may have contributed to the absence of a stimulus specificity effect. Experiment 2 assessed a separate habituation characteristic, rate of stimulation, to address these methodological concerns and further evaluate habituation. Twenty-eight participants completed the reinforcement paradigm over three visits. Decline in responding was partially supported, but the rate of stimulation did not alter declines. In sum, habituation's contribution to within-session declines for sensory reinforcers was not evident in either experiment. These results suggest that assessment of habituation of sensory reinforcers in humans may require parametric evaluation.