Exposure-Response Relationships during Free-Access Intravenous Alcohol Self-Administration in Nondependent Drinkers: Influence of Alcohol Expectancies and Impulsivity.

Background: Self-administration is a hallmark of all addictive drugs, including alcohol. Human laboratory models of alcohol self-administration have characterized alcohol-seeking behavior and served as surrogate measures of the effectiveness of pharmacotherapies for alcohol use disorders. Intravenous alcohol self-administration is a novel method that assesses alcohol exposure driven primarily by the pharmacological response to alcohol and may have utility in characterizing unique behavioral and personality correlates of alcohol-seeking and consumption. Methods: This study examined exposure-response relationships for i.v. alcohol self-administration, and the influence of impulsivity and alcohol expectancy, in healthy, nondependent drinkers (n=112). Participants underwent a 2.5-hour free-access i.v. alcohol self-administration session using the Computerized Alcohol Infusion System. Serial subjective response measures included the Drug Effects Questionnaire and Alcohol Urge Questionnaire. To characterize the motivational aspects of alcohol consumption prior to potential acute adaptation, the number of self-infusions in the first 30 minutes of the free-access session was used to classify participants as low- and high-responders. Results: High-responders showed greater subjective responses during i.v. alcohol self-administration compared with low responders, reflecting robust exposure-driven hedonic responses to alcohol. High-responders also reported heavier drinking patterns and lower scores for negative alcohol expectancies on the Alcohol Effects Questionnaire. High-responders also showed higher measures of impulsivity on a delayed discounting task, supporting previous work associating impulsivity with greater alcohol use and problems. Conclusions: These findings indicate that early-phase measures of free-access i.v. alcohol self-administration are particularly sensitive to the rewarding and motivational properties of alcohol and may provide a unique phenotypic marker of alcohol-seeking behavior.

A combined histological and MRI brain atlas of the common marmoset monkey, Callithrix jacchus.

The common marmoset, Callithrix jacchus, is of growing importance for research in neuroscience and related fields. In the present work, we describe a combined histological and magnetic resonance imaging (MRI) atlas constructed from the brains of two adult female marmosets. Histological sections were processed from Nissl staining and digitized to produce an atlas in a large format that facilitates visualization of structures with significant detail. Naming of identifiable brain structures was performed utilizing current terminology. The histological sections and a simplified schematic atlas are available online at http://udn.nichd.nih.gov/brainatlas_home.html.