A Multi-Modal Investigation of the Smoking Cessation Medication Varenicline: Dopaminergic Modulation of Reward Processing and Cognitive Control

Overview

Background: * Chronic nicotine exposure through cigarette smoking affects the level of the brain chemical dopamine. Smokers who attempt to quit experience lower levels of dopamine, which increases anxiety and triggers nicotine cravings that make quitting more difficult. * Varenicline (Chantix) is a smoking cessation medication that is designed to reduce nicotine craving and withdrawal by slightly increasing levels of dopamine in the brain. Research has shown that varenicline is a safe, well-tolerated, and effective treatment for nicotine dependence, but researchers are interested in learning more about how it affects the brain and its function. Functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) will help researchers study the brain s response to nicotine and varenicline. Objectives: \- To explore how varenicline affects brain function and behavioral performance in current smokers and healthy volunteers. Eligibility: \- Individuals between 18 and 55 years of age who are either current smokers (10 or more cigarettes per day) or healthy nonsmoking volunteers. Design: * The study will involve nine testing and research visits over 5 to 6 weeks. The first visit will provide an initial assessment and training on the tasks that will be completed during the study. * Six testing visits will involve fMRI and EEG measurements of brain activity. Each visit will contain two 2-hour scanning sessions, and each session will involve thinking tests. During these visits, participants will receive varenicline and placebo tablets, and wear nicotine patches and placebo patches that do not contain nicotine. Participants will not be told which tablet or patch they are given. This is a crossover study so all participants eventually get nicotine and placebo, as well as varenicline and placebo. * Two other visits involve different thinking tasks. These visits will not require fMRI or EEG scans.

Objective. Chronic nicotine exposure is thought to lead to alterations in the dopamine (DA) system that leaves smokers in a hypo-dopaminergic state during periods of abstinence. Varenicline (Chantix), a new efficacious smoking cessation medication, is thought to lead to a modest but sustained increase of DA release thereby reducing nicotine craving and withdrawal. While numerous studies have shown that varenicline is a safe, well-tolerated, and effective pharmacological treatment for nicotine dependence, studies exploring the neurophysiological impact of this drug in the human brain have not been conducted. This protocol will utilize an array of reward processing and cognitive control tasks to explore the effects of subtle DA manipulations (induced by smoking cessation, transdermal nicotine, and varenicline) on brain function and behavioral performance. Brain function will be assessed using functional magnetic resonance imaging (fMRI) and electroencephalography (EEG). Study Population. There will be two study populations: 1) healthy nicotine-dependent adults who smoke 10 or more cigarettes per day; and 2) healthy non-smoking, non-drug dependent controls. Participants must be generally healthy, right-handed, male or non-pregnant/non-lactating females between the ages of 18-55. Design. After being medically cleared and giving informed consent, each participant will complete several imaging visits (6 visits, on separate days) before and after taking varenicline. Two of these visits will take place before varenicline administration (baseline), two visits after a two-week varenicline dosing period (post-varenicline), and another two after a two-week placebo-pill period (post-placebo-pill). Each set of two scans will involve the randomized, double blind administration of a nicotine transdermal or placebo patch. fMRI and EEG data will be collected after patch application and will involve several tasks designed to probe brain regions in a corticolimbic circuit that may mediate aspects of reward-processing, learning, attention, goal-directed behaviors, and drug abuse. Outcome Measures. This study involves assessing neurophysiological and behavior differences between cohorts (smokers vs. non-smokers) and conditions (nicotine vs. placebo-patch; baseline vs. varenicline vs. placebo-pill). The primary outcome measures used to ascertain these differences will be: 1) percentage change in fMRI BOLD signal during performance of cognitive control and reward processing tasks; 2) change in ERP component (e.g., error-related negativity) amplitudes; 3) behavioral measures during task performance including reaction times and error rates; 4) scores on mood, personality, and smoking questionnaires; and 5) variations in genes related to nicotinic receptors and DA functioning.