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Sunday, March 11, 2007

Effects of craving and DRD4 VNTR genotype on the relative value of alcohol: an initial human laboratory study

Behav Brain Funct. 2007; 3: 11.
Published online 2007 February 19.

James MacKillop,corresponding author1,2

David P Menges,1

John E McGeary,3,2 and

Stephen A Lisman1

1Department of Psychology, State University of New York at Binghamton, PO Box 6000, Binghamton, NY 13902-6000, USA
2Center for Alcohol and Addiction Studies, Brown University, Box G-BH, Providence RI 02906, USA
3Providence Veteran Affairs Medical Center, Providence RI 02909, USA

corresponding authorCorresponding author.

James MacKillop: james_mackillop@brown.edu ; David P Menges: dmenges@eden.rutgers.edu ; John E McGeary: john_mcgeary@brown.edu ; Stephen A Lisman: slisman@binghamton.edu

Received December 1, 2006; Accepted February 19, 2007.

Abstract

Background
Craving for alcohol is a highly controversial subjective construct and may be clarified by Loewenstein's visceral theory, which emphasizes craving's behavioral effects on the relative value of alcohol. Based on the visceral theory, this study examined the effects of a craving induction on the relative value of alcohol as measured by a behavioral choice task. In addition, based on previous evidence of its role in the expression of craving, the influence of DRD4 VNTR genotype (DRD4-L vs. DRD4-S) was also examined.

Methods
Thirty-five heavy drinkers (54% male; 31% DRD4-L) were randomly assigned to receive either a craving induction (exposure to personally relevant alcohol cues) or a control induction (exposure to neutral cues), which was followed by an alcohol-money choice task. Participants were assessed for craving and positive/negative affect throughout the procedure, and relative value of alcohol was derived from participant choices for alcohol versus money. DRD4 VNTR status was assessed retrospectively via buccal samples using previously established protocols.

Results
Factorial analysis of the craving induction revealed that it was associated with significant increase in craving (p < .001), but not greater relative value of alcohol. Factorial analyses including DRD4 VNTR genotype of did not suggest an influence on reactivity to the craving induction, although this analysis was substantially compromised by small cell sample sizes. Continuous analyses revealed that craving was significantly associated with the relative value of alcohol (p < .05) and possession of the DRD4-L allele further amplified this relationship (p < .001).

Conclusion
These results are interpreted as generally supporting Loewenstein's visceral theory of craving and evidence of a functional role of DRD4 VNTR genotype in the expression of craving for alcohol. Methodological limitations, mechanisms underlying these findings, and future directions are discussed.

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