Time dependency of craving and response inhibition during nicotine abstinence

Is impulsivity related to attentional bias in cigarette smokers? An exploration across levels of nicotine dependency and deprivation

Research has largely focused on how attentional bias to smoking-related cues and impulsivity independently influence the development and maintenance of cigarette smoking, with limited exploration of the relationship between these mechanisms. The current experiments systematically assessed relationships between multiple dimensions of impulsivity and attentional bias, at different stages of attention, in smokers varying in nicotine dependency and deprivation. Nonsmokers (NS; n  = 26), light-satiated smokers (LS; n  = 25), heavy-satiated smokers (HS; n  = 23) and heavy 12-hour nicotine-deprived smokers (HD; n  = 30) completed the Barratt Impulsivity Scale, delayed discounting task, stop-signal task, information sampling task and a visual dot-probe assessing initial orientation (200 ms) and sustained attention (2000 ms) toward smoking-related cues. Sustained attention to smoking-related cues was present in both HS and LS, while initial orientation bias was only evident in HS. HS and LS also had greater levels of trait motor and nonplanning impulsivity and heightened impulsive choice on the delay discounting task compared with NS, while heightened trait attentional impulsivity was only found in HS. In contrast, in HD, nicotine withdrawal was associated with no attentional bias but heightened reflection impulsivity, poorer inhibitory control and significantly lower levels of impulsive choice relative to satiated smokers. Trait and behavioral impulsivity were not related to the extent of attentional bias to smoking-related cues at any stage of attention, level of nicotine dependency or state of deprivation. Findings have both clinical and theoretical implications, highlighting the unique and independent roles impulsivity and attentional bias may play at different stages of the nicotine addiction cycle.

Assessing combined effects of varenicline and N-acetylcysteine on reducing nicotine seeking in rats

Nicotine addiction is a chronic relapsing brain disorder, and cigarette smoking is the leading cause of preventable death in the United States. Currently, the most effective pharmacotherapy for smoking cessation is Varenicline (VRN), which reduces both positive and negative reinforcement by nicotine. Clinically, VRN attenuates withdrawal symptoms and promotes abstinence, but >50% of smokers relapse within 3 months following a quit attempt. This may indicate that VRN fails to ameliorate components of nicotine-induced neuroplasticity that promote relapse vulnerability. Animal models reveal that glutamate dysregulation in the nucleus accumbens is associated with nicotine relapse. N-acetylcysteine (NAC) normalizes glutamate transmission and prolongs cocaine abstinence. Thus, combining VRN and NAC may promote and maintain, respectively, nicotine abstinence. In rats, we found that VRN effectively reduced nicotine self-administration and seeking in early abstinence, but not seeking later in abstinence. In contrast, NAC reduced seeking only later in abstinence. Because VRN and NAC are sometimes associated with mild adverse effects, we also evaluated a sequential approach combining subthreshold doses of VRN during self-administration and early abstinence with subthreshold doses of NAC during late abstinence. As expected, subthreshold VRN did not reduce nicotine intake. However, subthreshold VRN and NAC reduced seeking in late abstinence, suggesting a combined effect. Overall, our results suggest that combining subthreshold VRN and NAC is a viable and drug-specific approach to promote abstinence and reduce relapse while minimizing adverse effects. Our data also suggest that different components and time points in addiction engage the different neurocircuits targeted by VRN and NAC.

The role of the SLC6A3 3' UTR VNTR in nicotine effects on cognitive, affective, and motor function

RATIONALE

Nicotine has been widely studied for its pro-dopaminergic effects. However, at the behavioural level, past investigations have yielded heterogeneous results concerning effects on cognitive, affective, and motor outcomes, possibly linked to individual differences at the level of genetics. A candidate polymorphism is the 40-base-pair variable number of tandem repeats polymorphism (rs28363170) in the SLC6A3 gene coding for the dopamine transporter (DAT). The polymorphism has been associated with striatal DAT availability (9R-carriers > 10R-homozygotes), and 9R-carriers have been shown to react more strongly to dopamine agonistic pharmacological challenges than 10R-homozygotes.

OBJECTIVES

In this preregistered study, we hypothesized that 9R-carriers would be more responsive to nicotine due to genotype-related differences in DAT availability and resulting dopamine activity.

METHODS

N=194 non-smokers were grouped according to their genotype (9R-carriers, 10R-homozygotes) and received either 2-mg nicotine or placebo gum in a between-subject design. Spontaneous blink rate (SBR) was obtained as an indirect measure of striatal dopamine activity and smooth pursuit, stop signal, simple choice and affective processing tasks were carried out in randomized order.

RESULTS

Reaction times were decreased under nicotine compared to placebo in the simple choice and stop signal tasks, but nicotine and genotype had no effects on any of the other task outcomes. Conditional process analyses testing the mediating effect of SBR on performance and how this is affected by genotype yielded no significant results.

CONCLUSIONS

Overall, we could not confirm our main hypothesis. Individual differences in nicotine response could not be explained by rs28363170 genotype.

A Randomised Controlled Trial of Inhibitory Control Training for Smoking Cessation: Outcomes, Mediators and Methodological Considerations

Objective: Inhibitory control training (ICT) has shown promise for improving health behaviours, however, less is known about its mediators of effectiveness. The current paper reports whether ICT reduces smoking-related outcomes such as craving and nicotine dependence, increases motivation to quit and whether reductions in smoking or craving are mediated by response inhibition or a devaluation of smoking stimuli.

Method: Adult smokers (minimum 10 cigarettes per day; N = 107, M_age = 46.15 years, 57 female) were randomly allocated to receive 14 days of smoking-specific ICT (named INST; a go/no-go task where participants were trained to not respond to smoking stimuli) or active control training (participants inhibited responding toward neutral stimuli). Participants were followed up to 3-months post-intervention. This trial was preregistered (Australian and New Zealand Clinical Trials Registry ID: ACTRN12617000252314; URL: https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=370204).

Results: There were no significant differences between ICT and active control training groups. Specifically, participants in both groups showed significant reductions in craving, nicotine dependence, motivation and a devaluation (reduced evaluation) of smoking-stimuli up to 3-months follow-up compared to baseline. Inhibition and devaluation of smoking stimuli did not act as mediators. Devaluation of smoking stimuli was an independent predictor of smoking and craving at follow-up.

Conclusion: Inhibitory control training (ICT) was no more effective at reducing smoking-related outcomes compared to the active control group, however, significant improvements in craving, dependence indicators and evaluation of smoking stimuli were observed across both groups. A return to basic experimental research may be required to understand the most effective ICT approach to support smoking cessation.

No differences in delay discounting between smokers with and without HIV

RATIONALE

People with HIV (PWH) smoke cigarettes at much higher rates than the general population and evidence-based cessation methods are less effective, putting PWH at greater risk for negative health outcomes. It is critical to identify the factors that underlie this health disparity. Delay discounting-the decline in the value of a reward when it is delayed-may explain this disparity.

OBJECTIVES

This study aimed to (1) compare delay discounting between adult smokers with HIV and without HIV and (2) evaluate whether acute smoking abstinence disproportionately increases delay discounting among smokers with HIV.

METHODS

This sub-study was part of a larger study (NCT03169101) examining predictors of smoking cessation outcomes among smokers with HIV (n = 34) and smokers without HIV (n = 46) at two counterbalanced laboratory sessions (once smoking-as-usual and once following 24-h biochemically confirmed abstinence) then again, after 8 weeks of smoking cessation treatment.

RESULTS

There were no significant differences in delay discounting rates between HIV status groups (p = 0.49) or within-subject abstinence effects (p = 0.70). However, smokers without HIV exhibited a significant increase in delay discounting following smoking cessation treatment compared to baseline (p = 0.02), whereas the change among smokers with HIV did not reach statistical significance (p = 0.09).

CONCLUSIONS

These findings do not support differences in delay discounting as a reason for the lower success rates of HIV+ smokers at quitting. Although delay discounting may not explain the disparity in smoking rates between people with and without HIV, future work should focus on additional correlates of higher smoking rates and lower quit rates among people with HIV.

Associations Between Smoking Abstinence, Inhibitory Control, and Smoking Behavior: An fMRI Study

Nicotine addiction is associated with dysregulated inhibitory control (IC), mediated by corticothalamic circuitry including the right inferior frontal gyrus (rIFG). Among sated smokers, worse IC task performance and greater IC-related rIFG activity have been shown to be associated with greater relapse vulnerability. The present study investigated the effects of smoking abstinence on associations between IC task performance, rIFG activation, and smoking behavior. Smokers (N = 26, 15 female) completed an IC task (Go/Go/No-go) during fMRI scanning followed by a laboratory-based smoking relapse analog task (SRT) on two visits: once when sated and once following 24 h of smoking abstinence. During the SRT, smokers were provided with monetary rewards for incrementally delaying smoking. A significant main effect of No-go accuracy on latency to smoke during the SRT was observed when collapsing across smoking states (abstinent vs. sated). Similarly, a significant main effect of IC-related activation in rIFG on SRT performance was observed across states. The main effect of state, however, was non-significant in both of these models. Furthermore, the interaction between smoking state and No-go accuracy on SRT performance was non-significant, indicating a similar relationship between IC and lapse vulnerability under both sated and abstinent conditions. The state X rIFG activation interaction on SRT performance was likewise non-significant. Post-hoc whole brain analyses indicated that abstinence resulted in greater IC-related activity in the right middle frontal gyrus (MFG) and insula. Activation during IC in these regions was significantly associated with decreased No-go accuracy. Moreover, greater abstinence induced activity in right MFG during IC was associated with smoking sooner on the SRT. These findings are bolstered by the extant literature on the effects of nicotine on executive function and also contribute novel insights on how individual differences in behavioral and neuroimaging measures of IC may influence relapse propensity independent of smoking state.

Assessment of the Choice Behavior Under Cued Conditions (CBUCC) paradigm as a measure of motivation to smoke under laboratory conditions

BACKGROUND AND AIMS

The Choice Behavior under Cued Conditions (CBUCC) task uses three indices of tobacco use (consumption, money spent to access a cigarette and latency to reach for a cigarette) to assess motivation to smoke under laboratory conditions. Initial research with this procedure has shown that it can evince cue-specific craving and differential responding for smoking versus a neutral cue. This study aimed to replicate these findings and assess the interaction of cue-specific craving and behavior with abstinence prior to testing.

DESIGN

A mixed repeated-measures between-groups factorial design was used. Participants attended a morning laboratory session in which they were randomized to remain abstinent or smoke as usual (between-groups factor) and returned in the afternoon to complete CBUCC. In this, participants were exposed to 40 experimental trials. In each trial they were exposed to a cigarette or water cue behind a movable glass door (repeated-measures factor).

SETTING

University at Buffalo, New York, USA.

PARTICIPANTS

Participants were 106 daily non-treatment-seeking cigarette smokers, data from 102 were used.

MEASUREMENTS

On each of 40 trials, participants rated cigarette craving, and behavioral measures from the CBUCC (money spent, latency to access the cue, puff duration) were recorded.

FINDINGS

Craving and CBUCC behavioral measures showed high internal reliability across trials (Cronbach alphas ranged from 0.88 to 0.98). Craving and money spent were higher in trials with the cigarette cue than the water cue (F₍₁₁₀₀₎  = 45.49, P < 0.001 and F₍₁₁₀₀₎  = 116.26, P < 0.001). Other CBUCC measures did not show a significant effect of cue type. The difference in spending between cigarette and water cues was larger for abstinent participants than non-abstinent participants (F₍₁₁₀₀₎  = 5.0, P = 0.03). Other CBUCC measures did not show a significant interaction between abstinence and cue type. Craving on smoking trials was significantly correlated with cigarette spending (r = 0.54, P < 0.001) in the non-abstinence condition but not in the abstinence condition.

CONCLUSIONS

Craving and 'money spent' in the Choice Behavior under Cued Conditions task (CBUCC) appears to be responsive to cigarette versus water cues, and money spent appears to show greater difference in responsiveness to cigarette than water cues after abstinence.

Effects of nicotine and atomoxetine on brain function during response inhibition

The nicotinic acetylcholine receptor (nAChR) agonist nicotine and the noradrenaline transporter inhibitor atomoxetine are widely studied substances due to their propensity to alleviate cognitive deficits in psychiatric and neurological patients and their beneficial effects on some aspects of cognitive functions in healthy individuals. However, despite growing evidence of acetylcholine-noradrenaline interactions, there are only very few direct comparisons of the two substances. Here, we investigated the effects of nicotine and atomoxetine on response inhibition in the stop-signal task and we characterised the neural correlates of these effects using blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI) at 3T. Nicotine (7 mg dermal patch) and atomoxetine (60 mg per os) were applied to N = 26 young, healthy adults in a double-blind, placebo-controlled, cross-over, within-subjects design. BOLD images were collected during a stop-signal task that controlled for infrequency of stop trials. There were no drug effects on behavioural performance or subjective state measures. However, there was a pronounced upregulation of activation in bilateral prefrontal and left parietal cortex following nicotine during successful compared to unsuccessful stop trials. The effect of nicotine on BOLD during failed stop trials was correlated across individuals with a measure of trait impulsivity. Atomoxetine, however, had no discernible effects on BOLD. We conclude that nicotine effects on brain function during inhibitory control are most pronounced in individuals with higher levels of impulsivity. This finding is compatible with previous evidence of nicotine effects on stop-signal task performance in highly impulsive individuals and implicates the nAChR in the neural basis of impulsivity.

Cue-induced nicotine-seeking behavior after withdrawal with or without extinction in rats

Exposure to smoking-associated environmental cues during smoke cessation elicits self-reported urge/craving to smoke, which precipitates relapse even after prolonged abstinence. Incubation of cue-induced cigarettes craving during abstinence has been observed in human smokers recently. The present studies assessed cue-induced nicotine-seeking behavior under different withdrawal conditions in rats with a history of nicotine self-administration. We found that non-reinforced operant responding during cue-induced nicotine seeking after different periods of withdrawal from nicotine exhibited an inverted U-shaped curve, with higher levels of responding after 7-21 days of withdrawal than those after 1-day withdrawal. Cue-induced nicotine-seeking responding is long lasting and persists even after 42 days of forced withdrawal in the home cages. Interestingly, repeated testing of cue-induced nicotine seeking at different withdrawal time points (1, 7, 14, 21 and 42 days) in the same individual alleviated responding as compared with the between-subjects assessment. Furthermore, extinction training during nicotine withdrawal significantly decreased cue-induced reinstatement of nicotine-seeking behavior. Together, profound time-dependent incubation of cue-induced craving in nicotine-experienced rats were observed. In addition, repeated cue exposure or extinction training decreases cue-induced craving. The demonstration of incubation of nicotine craving phenomenon in both rat and human studies provides support for the translational potential of therapeutic targets for relapse uncovered through mechanism studies in rats.

Nicotine withdrawal-induced inattention is absent in alpha7 nAChR knockout mice

RATIONALE

Smoking is the leading cause of preventable death in the USA, but quit attempts result in withdrawal-induced cognitive dysfunction and predicts relapse. Greater understanding of the neural mechanism(s) underlying these cognitive deficits is required to develop targeted treatments to aid quit attempts.

OBJECTIVES

We examined nicotine withdrawal-induced inattention in mice lacking the α7 nicotinic acetylcholine receptor (nAChR) using the five-choice continuous performance test (5C-CPT).

METHODS

Mice were trained in the 5C-CPT prior to osmotic minipump implantation containing saline or nicotine. Experiment 1 used 40 mg kg-1 day-1 nicotine treatment and tested C57BL/6 mice 4, 28, and 52 h after pump removal. Experiment 2 used 14 and 40 mg kg-1 day-1 nicotine treatment in α7 nAChR knockout (KO) and wildtype (WT) littermates tested 4 h after pump removal. Subsets of WT mice were killed before and after pump removal to assess changes in receptor expression associated with nicotine administration and withdrawal.

RESULTS

Nicotine withdrawal impaired attention in the 5C-CPT, driven by response inhibition and target detection deficits. The overall attentional deficit was absent in α7 nAChR KO mice despite response disinhibition in these mice. Synaptosomal glutamate mGluR5 and dopamine D4 receptor expression were reduced during chronic nicotine but increased during withdrawal, potentially contributing to cognitive deficits.

CONCLUSIONS

The α7 nAChR may underlie nicotine withdrawal-induced deficits in target detection but is not required for response disinhibition deficits. Alterations to the glutamatergic and dopaminergic pathways may also contribute to withdrawal-induced attentional deficits, providing novel targets to alleviate the cognitive symptoms of withdrawal during quit attempts.

Life adversity is associated with smoking relapse after a quit attempt

Multiple cross-sectional studies have linked adverse childhood events and adult adversities to current smoking, lifetime smoking, and former smoking. To date, however, there have been no direct observational studies assessing the influence of adversities on smoking relapse. We prospectively followed 123 participants, 86 of whom were habitual smokers, from pre-quit ad libitum smoking to four weeks post-quit. Thirty-seven non-smokers were also tested in parallel as a comparison group. Subjects provided biological samples for confirmation of abstinence status and self-report history of adversities such as abuse, neglect, family dysfunction, incarceration, and child-parent separation. They also completed mood and smoking withdrawal symptom measures. The results indicated that within non-smokers and smokers who relapsed within the first month of a quit attempt, but not abstainers, females had significantly higher adversity scores than males. Cigarette craving, which was independent from depressive affect, increased for low adversity participants, but not those with no adversity nor high adversity. These results demonstrate that sex and relapse status interact to predict adversity and that craving for nicotine may be an important additional mediator of relapse. These results add further support to the previous cross-sectional evidence of an adversity and smoking relationship. Further studies to clarify how adversity complicates smoking cessation and impacts smoking behaviors are warranted.

Cognitive Dysfunction, Affective States, and Vulnerability to Nicotine Addiction: A Multifactorial Perspective

Although smoking prevalence has declined in recent years, certain subpopulations continue to smoke at disproportionately high rates and show resistance to cessation treatments. Individuals showing cognitive and affective impairments, including emotional distress and deficits in attention, memory, and inhibitory control, particularly in the context of psychiatric conditions, such as attention-deficit hyperactivity disorder, schizophrenia, and mood disorders, are at higher risk for tobacco addiction. Nicotine has been shown to improve cognitive and emotional processing in some conditions, including during tobacco abstinence. Self-medication of cognitive deficits or negative affect has been proposed to underlie high rates of tobacco smoking among people with psychiatric disorders. However, pre-existing cognitive and mood disorders may also influence the development and maintenance of nicotine dependence, by biasing nicotine-induced alterations in information processing and associative learning, decision-making, and inhibitory control. Here, we discuss the potential forms of contribution of cognitive and affective deficits to nicotine addiction-related processes, by reviewing major clinical and preclinical studies investigating either the procognitive and therapeutic action of nicotine or the putative primary role of cognitive and emotional impairments in addiction-like features.