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Reward Anticipation Is Differentially Modulated by Varenicline and Nicotine in Smokers.

ABSTRACT: Recidivism rates for cigarette smokers following treatment often exceed 80%. Varenicline is the most efficacious pharmacotherapy currently available with cessation rates of 25-35% following a year of treatment. Although the in vivo binding properties are well known, varenicline's neurobiological mechanisms of action are still poorly understood. Varenicline acts as a nicotinic receptor partial agonist or antagonist depending on the presence or absence of nicotine and has been implicated in the reduction of reward signaling more broadly. The current study probed anticipatory reward processing using a revised monetary incentive delay task during fMRI in cohorts of smokers and non-smokers who completed a two-drug, placebo-controlled, double-blind crossover study. All participants underwent ~17 days of order-balanced varenicline and placebo pill administration and were scanned under each condition wearing a transdermal nicotine or placebo patch. Consistent with nicotine's ability to enhance the rewarding properties of nondrug stimuli, acute nicotine administration enhanced activation in response to reward-predicting monetary cues in both smokers and non-smokers. In contrast, varenicline reduced gain magnitude processing, but did so only in smokers. These results suggest that varenicline's downregulation of anticipatory reward processing in smokers, in addition to its previously demonstrated reduction in the negative affect associated with withdrawal, independently and additively alter distinct brain circuits. These effects likely contribute to varenicline's efficacy as a pharmacotherapy for smoking cessation.

SUBMITTER: Fedota JR

PROVIDER: S-EPMC4839527 | biostudies-literature | 2015 Jul

REPOSITORIES: biostudies-literature

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Reward Anticipation Is Differentially Modulated by Varenicline and Nicotine in Smokers.

Fedota John R JR Sutherland Matthew T MT Salmeron Betty Jo BJ Ross Thomas J TJ Hong L Elliot LE Stein Elliot A EA

Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology 20150306 8

Recidivism rates for cigarette smokers following treatment often exceed 80%. Varenicline is the most efficacious pharmacotherapy currently available with cessation rates of 25-35% following a year of treatment. Although the in vivo binding properties are well known, varenicline's neurobiological mechanisms of action are still poorly understood. Varenicline acts as a nicotinic receptor partial agonist or antagonist depending on the presence or absence of nicotine and has been implicated in the re ...[more]

PMID: 25742873

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Project description:ImportanceQuitting smoking is enhanced by the use of pharmacotherapies, but concerns have been raised regarding the cardiovascular safety of such medications.ObjectiveTo compare the relative cardiovascular safety risk of smoking cessation treatments.Design, setting, and participantsA double-blind, randomized, triple-dummy, placebo- and active-controlled trial (Evaluating Adverse Events in a Global Smoking Cessation Study [EAGLES]) and its nontreatment extension trial was conducted at 140 multinational centers. Smokers, with or without established psychiatric diagnoses, who received at least 1 dose of study medication (n = 8058), as well as a subset of those who completed 12 weeks of treatment plus 12 weeks of follow up and agreed to be followed up for an additional 28 weeks (n = 4595), were included.InterventionsVarenicline, 1 mg twice daily; bupropion hydrochloride, 150 mg twice daily; and nicotine replacement therapy, 21-mg/d patch with tapering.Main outcomes and measuresThe primary end point was the time to development of a major adverse cardiovascular event (MACE: cardiovascular death, nonfatal myocardial infarction, or nonfatal stroke) during treatment; secondary end points were the occurrence of MACE and other pertinent cardiovascular events (MACE+: MACE or new-onset or worsening peripheral vascular disease requiring intervention, coronary revascularization, or hospitalization for unstable angina).ResultsOf the 8058 participants, 3553 (44.1%) were male (mean [SD] age, 46.5 [12.3] years). The incidence of cardiovascular events during treatment and follow-up was low (<0.5% for MACE; <0.8% for MACE+) and did not differ significantly by treatment. No significant treatment differences were observed in time to cardiovascular events, blood pressure, or heart rate. There was no significant difference in time to onset of MACE for either varenicline or bupropion treatment vs placebo (varenicline: hazard ratio, 0.29; 95% CI, 0.05-1.68 and bupropion: hazard ratio, 0.50; 95% CI, 0.10-2.50).Conclusions and relevanceNo evidence that the use of smoking cessation pharmacotherapies increased the risk of serious cardiovascular adverse events during or after treatment was observed. The findings of EAGLES and its extension trial provide further evidence that smoking cessation medications do not increase the risk of serious cardiovascular events in the general population of smokers.Trial registrationclinicaltrials.gov Identifier: NCT01574703.

Project description:BackgroundAlthough the amygdala and insula are regarded as critical neural substrates perpetuating cigarette smoking, little is known about their circuit-level interactions with interconnected regions during nicotine withdrawal or following pharmacotherapy administration. To elucidate neurocircuitry associated with early smoking abstinence, we examined the impact of varenicline and nicotine, two modestly efficacious pharmacologic cessation aids, on amygdala- and insula-centered circuits using resting-state functional connectivity (rsFC).MethodsIn a functional magnetic resonance imaging study employing a two-drug, placebo-controlled design, 24 overnight-abstinent smokers and 20 nonsmokers underwent ∼17 days of varenicline and placebo pill administration and were scanned, on different days under each condition, wearing a transdermal nicotine or placebo patch. We examined the impact of varenicline and nicotine (both alone and in combination) on amygdala- and insula-centered rsFC using seed-based assessments.ResultsBeginning with a functionally defined amygdala seed, we observed that rsFC strength in an amygdala-insula circuit was down-regulated by varenicline and nicotine in abstinent smokers. Using this identified insula region as a new seed, both drugs similarly decreased rsFC between the insula and constituents of the canonical default-mode network (posterior cingulate cortex, ventromedial/dorsomedial prefrontal cortex, parahippocampus). Drug-induced rsFC modulations were critically linked with nicotine withdrawal, as similar effects were not detected in nonsmokers.ConclusionsThese results suggest that nicotine withdrawal is associated with elevated amygdala-insula and insula-default-mode network interactions. As these potentiated interactions were down-regulated by two pharmacotherapies, this effect may be a characteristic shared by pharmacologic agents promoting smoking cessation. Decreased rsFC in these circuits may contribute to amelioration of subjective withdrawal symptoms.

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Reward Anticipation Is Differentially Modulated by Varenicline and Nicotine in Smokers.

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Reward Anticipation Is Differentially Modulated by Varenicline and Nicotine in Smokers.

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