Nicotine Reinforcement and Aversion in Young Adult Light Smokers

Overview

The proposed study will examine the threshold for nicotine self-administration (NSA) using five different nicotine doses in young adult male and female non-dependent smokers (light and intermittent smokers or LITS). We propose a double-blind, placebo-controlled study that will enroll 195 individuals, targeting a total of 72 completers (36 male and 36 females). In each of the five experimental sessions, smokers will be randomly assigned to one of the five doses of nicotine (0.0125, 0.025, 0.05, 0.1 and 0.2 mg/70 kg). The highest dose, 0.2 mg/70 kg, corresponds to nicotine delivered by about one or two puffs of a cigarette. At the beginning of each experimental session, smokers will sample the assigned both the nicotine dose for that experimental session, and the placebo (saline) dose, followed by the opportunity to choose between nicotine and placebo for a total of ten choices over a 150-minute period. The main outcomes will be threshold dose (the minimum dose of nicotine that is self-administered more than placebo) and the slope of dose-response for nicotine self-administration (changes in nicotine self-administration per unit change in nicotine dose). We will also collect measures of nicotine intake (cotinine), nicotine clearance (3-hydroxycotinine (3-HC) / cotinine), and self-report drug effects

Aim #1: To assess the threshold reinforcing dose and dose-effect curve for IV NSA at low doses in young adult LITS. Hypothesis #1A: The threshold reinforcing doses for IV NSA will be between 0.0125 to 0.1 mg/70 kg. Hypothesis #1B: The dose-effect curve for NSA will differ between males and females with relatively flat curve in female smokers. Aim #2: To assess the threshold and dose-effect curve for the positive and negative/aversive subjective effects of IV nicotine at low doses and its relationship to nicotine reinforcement. Hypothesis #2 A: The threshold for the positive effects will be between 0.0125 to 0.1 mg/70 kg, for the negative/aversive effect it will be ≥ 0.1 mg/70 kg. Hypothesis #2B: Nicotine reinforcement will be positively correlated with the positive and negatively correlated with the negative/aversive subjective effects of IV nicotine. Exploratory Aims: To examine the influence of nicotine clearance rate on nicotine reinforcement threshold and dose-effect curve.