Objective: The goal of this project is to characterize the computer-assisted self-administration of ethanol (CASE) paradigm by assessing intravenous (IV) alcohol self-administration behavior and the resulting breath alcohol concentration (BrAC) exposure and pharmacologic responses in humans. The study will also evaluate the test-retest reliability of alcohol self-administration and examine the influence of sex and recent drinking history, as well as the effect of acute stress cues on alcohol self-administration. Additionally, this study will test whether a novel experimental paradigm can be used to evaluate impaired control in
heavy drinkers.
Study population: Participants will be 21-60 year-old male and female social drinkers, binge drinkers and heavy drinkers in good health, as determined by medical history, physical exam, ECG and lab tests. Participants with Axis-I psychiatric illness (other than alcohol use disorder for Group 6) will be excluded.
Design: The CASE system utilizes a model-based algorithm based on previously published methods to achieve and maintain pre-determined BrACs using IV alcohol infusions. The CASE system provides flexibility to participants in choosing when to push a button to receive alcohol, as well as flexibility to investigators in controlling the subsequent BrAC exposure. The CASE system allows the investigator to specify and assure the same BrAC increment across all participants, and is set up to prevent the BrAC from exceeding any pre-set upper limit (e.g., 120 mg%).
Following screening, participants will undergo IV ethanol self-administration sessions. Participants will be enrolled in six groups: Group 1 will consist of the first 10 participants who will participate in 3 self-administration sessions (a training session followed by 2 test sessions) to assess the test-retest reliability of alcohol self-administration behavior. Group 2 will consist of 50 participants, who will each participate in 2 self-administration sessions (a training session followed by a test session). During each session, participants will first undergo a directed priming period, lasting 25 min, where they will be prompted to push a button to receive small standardized alcohol infusions. This will be followed by an ad-lib period, lasting up to 2 hrs, where they will have free access to standardized IV alcohol infusions. During the session, BrAC will be measured, heart-rate will be continuously recorded, and subjective perceptions of alcohol effects and urges will be assessed. Group 3 will consist of 15 participants, who will undergo two identical progressive work self-administration sessions for evaluation of test-retest reliability. During each progressive ratio (PR) schedule session, participants will be required to push the button progressively higher number of times for each subsequent alcohol infusion over a 2.5 hr period. Group 4 will consist of 100 participants, who will each participate in 2 sessions: one ad lib self-administration session and one PR schedule self-administration session. Group 5 will consist of 40 participants, who will undergo a baseline self-administration session followed by an interview session for construction of guided imagery scripts. Following this, participants will undergo three alcohol self-administration sessions, following exposure to personalized stress-, alcohol- or neutral-condition associated scripts, presented in randomized order on separate days. Group 6a will consist of a maximum of 15 participants who will undergo a baseline self-administration session followed by an experimental session in which they will be given the opportunity to resist receiving self-infusions of alcohol in return for monetary reinforcers. Group 6b will consist of 37 participants who will complete a baseline self-administration session followed by two experimental sessions, with and without a priming dose of alcohol, and two follow up visits. Group 6 participants will also be given an ecological momentary assessment (EMA) device and will complete random assessments of real-world measures of impaired control and alcohol consumption per day for the duration of the study.
Outcome measures: The primary endpoint is the BrAC exposure (highest BrAC, average BrAC, area-under-the-BrAC-time-curve) achieved during the self-administration session. Additionally, changes in subjective perceptions of alcohol effects, as well as changes in heart rate will be evaluated. The influence of sex and recent drinking history as well as genetic polymorphisms on the self-administration of alcohol will also be examined. Furthermore, individual-specific cellular responses to alcohol exposure will be examined using induced pluripotent stem cells (iPSCs) from participants selected based on genotypic and phenotypic variation in self-administration measures. Outcome measures for group 5 will include stress and alcohol cue-induced craving and self-administration. Human laboratory outcome
measures for Group 6 will include time to lapse during the delay phase, number of infusions,
peak BrAC, and average BrAC during the ad-libitum phase. EMA outcomes will include
total alcohol consumption, number of impaired control episodes, and severity of impaired
control episodes. The CASE paradigm can be a valuable tool for evaluating determinants that may underlie self-administration behavior in humans. The effect of pharmacological agents on alcohol self-administration can be evaluated as a marker of the clinical effectiveness of these agents in the treatment of alcohol-dependence.