Reinforcement Enhancing Effects of Nicotine Via Patch and Nasal Spray

Individual variations in motives for nicotine self-administration in male rats: evidence in support for a precision psychopharmacology

The significant heterogeneity in smoking behavior among smokers, coupled with the inconsistent efficacy of approved smoking cessation therapies, supports the presence of individual variations in the mechanisms underlying smoking. This emphasizes the need to shift from standardized to personalized smoking cessation therapies. However, informed precision medicine demands precision fundamental research. Tobacco smoking is influenced and sustained by diverse psychopharmacological interactions between nicotine and environmental stimuli. In the classical experimental rodent model for studying tobacco dependence, namely intravenous self-administration of nicotine, seeking behavior is reinforced by the combined delivery of nicotine and a discrete cue (nicotine+cue). Whether self-administration behavior is driven by the same psychopharmacological mechanisms across individual rats remains unknown and unexplored. To address this, we employed behavioral pharmacology and unbiased cluster analysis to investigate individual differences in the mechanisms supporting classical intravenous nicotine self-administration (0.04 mg/kg/infusion) in male outbred Sprague-Dawley rats. Our analysis identified two clusters: one subset of rats sought nicotine primarily for its reinforcing effects, while the second subset sought nicotine to enhance the reinforcing effects of the discrete cue. Varenicline (1 mg/kg i.p.) reduced seeking behavior in the former group, whereas it tended to increase in the latter group. Crucially, despite this fundamental qualitative difference revealed by behavioral manipulation, the two clusters exhibited quantitatively identical nicotine+cue self-administration behavior. The traditional application of rodent models to study the reinforcing and addictive effects of nicotine may mask individual variability in the underlying motivational mechanisms. Accounting for this variability could significantly enhance the predictive validity of translational research.

Learning to quit: can reinforcement theories predict the success of smoking cessation attempts using nicotine replacement therapy patches in a general population sample of smokers at 8-weeks and 6-months follow-up?

Primary, secondary, and tertiary reinforcement contribute to the maintenance of smoking behaviour and may influence the efficacy of different cessation treatments. This analysis examined these relationships in a large general population sample and investigated how previous experiences of the different reinforcement mechanisms impacted future quit attempts. Random digit telephone dialing was used to recruit a sample of Canadian adults who smoked and were interested in being part of a hypothetical program that would provide nicotine replacement therapy (NRT) patches free by mail and half of the eligible participants were randomized to actually receive a five-week supply of NRT patches. During the interviews, reasons for relapse to smoking during previous quit attempts were collected and coded by two reviewers (disagreements were settled by a third reviewer). Binary logistic regression was used to determine if type of reinforcer moderated the intervention effect of the patches. Participants who made cessation attempts in the past year were more likely to report negative (p = .039), secondary (p = .041), and tertiary (p = .010) reinforcers and less likely to report positive reinforcers (p = .016) compared to those who did not attempt to quit. Logistic regressions revealed no significant conditional effects of the intervention on the relationship between reinforcer type and quit attempts or 30-day smoking abstinence. Analysis including all three reinforcers showed negative reinforcers decreased but tertiary reinforcers increased the odds participants reported a cessation attempt before the baseline interview and between baseline and 8-weeks. Understanding the different ways nicotine reinforces smoking behaviour could help guide individuals to more effective treatment options.

Elucidating the reinforcing effects of nicotine: a tribute to Nadia Chaudhri

Nadia Chaudhri worked with us as a graduate student in the Center for Neuroscience at the University of Pittsburgh from 1999 until she earned her PhD in 2005, a time that coincided with the discovery in our lab of the dual reinforcing actions of nicotine, a concept that she played an important role in shaping. The research that was described in her doctoral thesis is among the foundational pillars of the now well-accepted notion that nicotine acts as both a primary reinforcer and an amplifier of other reinforcer stimuli. This reinforcement-enhancing action of nicotine is robust and likely to be a powerful driver of nicotine use. Below, we discuss the evidence that these two actions of nicotine - primary reinforcement and reinforcement enhancement - are distinct and dissociable, a finding that Nadia was closely associated with. We go on to address two other topics that greatly interested Nadia during that time, the generalizability of the reinforcement-enhancing action of nicotine to multiple classes of reinforcing stimuli and potential sex differences in the dual reinforcing actions of nicotine. The research has greatly expanded since Nadia's involvement, but the core ideas that she helped to develop remain central to the concept of the dual reinforcing actions of nicotine and its importance for understanding the drivers of nicotine use.

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).

The incentive amplifying effects of nicotine: Roles in alcohol seeking and consumption

Nicotine has a unique profile among drugs of abuse. To the noninitiated user, nicotine has powerful aversive effects and its relatively weak euphorigenic effects undergo rapid tolerance. Despite this, nicotine is commonly abused despite negative heath consequences, and nicotine users have enormous difficulty quitting. Further, nicotine is one of the most commonly co-abused substances, in that it is often taken in combination with other drugs. One explanation of this polydrug use is that nicotine has multiple appetitive and consummatory conditioning effects. For example, nicotine is a reinforcement enhancer in that it can potently increase the incentive value of other stimuli, including those surrounding drugs of abuse such as alcohol. In addition, nicotine also has a unique profile of neurobiological effects that alter regulation of alcohol intake and interoception. This review discusses the psychological and biological mechanisms surrounding nicotine's appetitive conditioning and consummatory effects, particularly its interactions with alcohol.

Reliability and validity of a transdiagnostic measure of reward valuation effort

To identify biobehavioral mechanisms underlying excessive reward consumption, reward valuation-effort (RV-E) assessments should (a) parallel measures in basic science to permit translation from preclinical to clinical studies; (b) quantify constructs dimensionally from healthy to disease states; and (c) hold relevance across different diagnostic categories. To address these aims, we developed a progressive ratio (PR) task whereby RV-E is measured as breakpoint when participants worked for access to playing a game. We evaluated test-retest reliability of breakpoint and convergent and discriminant validity of interpretations of this score against an established PR task for food. In Study 1, female undergraduates (N = 71; 33% racial minority; 28% ethnic minority) completed the game and food tasks in fasted and fed states. In Study 2, women (N = 189; 29% racial minority; 27% ethnic minority) with eating disorders (n = 158) were compared to controls (n = 31) on tasks. Game task breakpoint demonstrated excellent test-retest reliability, intraclass correlation coefficient (ICC) = .91, 95% CI [.80, -.96], over 2 weeks and convergent validity with the fasted food task (r = .51, p < .001). Consistent with animal models, breakpoint was lower in fed compared to fasted states across tasks, B (SE) = 321.01 (552.40), p < .001. Finally, the game task demonstrated discriminant validity from measurement of satiation. In Study 2, women with eating disorders demonstrated higher breakpoint on both tasks compared to controls, and game PR task breakpoint decreased from a fasted to fed state. The game PR task offers a novel approach for translating results from animal models of RV-E into testable hypotheses in nonclinical and clinical samples. (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.

Investigating sex differences and the effect of drug exposure order in the sensory reward-enhancing effects of nicotine and d-amphetamine alone and in combination

Nicotine enhances the rewarding effects of other environmental stimuli; this reward-enhancement encourages and maintains nicotine consumption. Nicotine use precedes other psychostimulant use, but receiving a stimulant prescription also predicts future smoking. Previously, no study has investigated effects of drug exposure order in reward-enhancement, nor with nicotine and d-amphetamine. Thus, we aimed to investigate how drug exposure order impacted the reward-enhancing effects of nicotine and d-amphetamine, alone and in combination. We used 20 male and 20 female Sprague-Dawley rats. Enhancement was investigated within-subjects by examining responding maintained by a visual stimulus reinforcer following a pre-session injection of either d-amphetamine (Sal, 0.1, 0.3, or 0.6 mg/kg) or nicotine (Sal, 0.03, 0.06, 0.1, 0.3 mg/kg). Twenty rats (10 M, 10 F) completed enhancement testing with nicotine before d-amphetamine. The other 20 rats (10 M, 10 F) completed testing with d-amphetamine before nicotine. Following these phases, rats were then given two pre-session injections: one of d-amphetamine (Sal, 0.1, 0.3, or 0.6 mg/kg) and another of nicotine (Sal, 0.03, 0.06, 0.1, or 0.3 mg/kg). Experiencing amphetamine before nicotine increased reward-enhancing effects of nicotine. Females exhibited greater effects of d-amphetamine on reward-enhancement, with no effect of exposure order. During the interaction phase, receiving nicotine before amphetamine enhanced the interaction between nicotine and d-amphetamine for females whereas amphetamine before nicotine heightened this interaction for males. From this, prior and current amphetamine use, in addition to sex, should be considered when treating nicotine dependency and when examining factors driving poly-substance use involving nicotine and d-amphetamine. Keywords: Adderall, ADHD, Dexedrine, operant, smoking, polysubstance use.

Applying design of experiments (DoE) on the properties of buccal film for nicotine delivery

Design of experiments is used to optimize ratios between deproteinized natural rubber latex, Eudragit® NM 30 D, and pectin for nicotine buccal film with dependent variables as moisture content, moisture uptake, and swelling index in simulated saliva 3 and 5 h. Mathematical models were linear for moisture content and moisture uptake, while swelling index in simulated saliva 3 and 5 h was a quadratic model. Optimized polymer ratio was 0.319:0.362:0.319, respectively. Experimental values were 13.17 ± 0.92%, 3.96 ± 0.84%, 112.58 ± 22.63%, and 124.69 ± 8.01% for dependent variables, respectively. The buccal film showed high swelling at pH 7 and swelling–deswelling behaviors in a water/ethanol environment. The surface pH, weight, and thickness were 8.11, 63.28 ± 6.18 mg, and 219.87 ± 44.28 µm, respectively. Nicotine content was found as 10.22 ± 0.46 mg/4 cm2. Maximum cumulative nicotine release was 9.82 ± 0.94 mg/4 cm2. Kinetic model fitted to the Korsmeyer-Peppas model and release exponent was 0.36, representing that release mechanism was controlled by Fickian diffusion release.

Reward-enhancing effects of d-amphetamine and its interactions with nicotine were greater in female rats and persisted across schedules of reinforcement

Nicotine enhances the value of environmental stimuli and rewards, and reward enhancement can maintain nicotine consumption. Stimulants such as d-amphetamine are misused more by women and are commonly co-used with nicotine. d-Amphetamine potentiates nicotine's effects in human and animal research. To date, there are no published studies examining this interaction in a reward-enhancement task. The current study sought to investigate the reward-enhancing effects of nicotine alongside and coadministered with d-amphetamine. Further, we evaluated the persistence of reward enhancement across ratio and temporal schedules of reinforcement. We used 10 male and 10 female Sprague-Dawley rats. Enhancement was assessed within subjects by examining active lever pressing for a visual stimulus reinforcer on variable ratio 3, variable interval 30 s and variable time 30 s - variable ratio 3 schedules. Before 1-h sessions, rats received one injection of saline, 0.1 or 0.3 mg/kg d-amphetamine and one of saline or 0.4 mg/kg nicotine, making six possible drug combinations (saline + saline, saline + nicotine, 0.1 d-amphetamine + aline, 0.1 d-amphetamine + nicotine, 0.3 d-amphetamine + saline and 0.3 d-amphetamine + nicotine) experienced in a randomized order by each rat. When d-amphetamine was coadministered with nicotine, we found an interaction effect on reward enhancement that persisted across schedules of reinforcement. Males and females exhibited reward enhancement by 0.3 d-amphetamine, while only females showed reward enhancement by 0.1 d-amphetamine. Further, females responded more for the visual stimulus than males in all d-amphetamine conditions. Future studies should assess how reward enhancement is involved in high nicotine-amphetamine comorbidity rates and enhanced amphetamine misuse in women.

Nicotine and alcohol: the role of midbrain dopaminergic neurons in drug reinforcement

Nicotine and alcohol addiction are leading causes of preventable death worldwide and continue to constitute a huge socio-economic burden. Both nicotine and alcohol perturb the brain's mesocorticolimbic system. Dopamine (DA) neurons projecting from the ventral tegmental area (VTA) to multiple downstream structures, including the nucleus accumbens, prefrontal cortex, and amygdala, are highly involved in the maintenance of healthy brain function. VTA DA neurons play a crucial role in associative learning and reinforcement. Nicotine and alcohol usurp these functions, promoting reinforcement of drug taking behaviors. In this review, we will first describe how nicotine and alcohol individually affect VTA DA neurons by examining how drug exposure alters the heterogeneous VTA microcircuit and network-wide projections. We will also examine how coadministration or previous exposure to nicotine or alcohol may augment the reinforcing effects of the other. Additionally, this review briefly summarizes the role of VTA DA neurons in nicotine, alcohol, and their synergistic effects in reinforcement and also addresses the remaining questions related to the circuit-function specificity of the dopaminergic system in mediating nicotine/alcohol reinforcement and comorbidity.