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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.joep.2008.07.005 Byline: Brian E. Roe (a), Timothy C. Haab (a), David Q. Beversdorf (b), Howard H. Gu (c), Michael R. Tilley (d) Keywords: Neuroimaging; Genetics; Selection bias; Risk attitudes; Experimental subjects Abstract: Techniques such as neuroimaging and molecular genetics are increasingly used to investigate economic theory, decision making behavior and personality traits related to economic behavior (e.g., risk attitudes, reward dependence). The generalizability of this research is ultimately limited, however, if the subjects participating in such studies are not representative of the general population with respect to the behavior or traits of interest to the researcher. In this study, university student recruits answer surveys that assess risk attitudes prior to being told that the study involves a one-hour functional magnetic resonance imaging (fMRI) session and a blood sample obtained via phlebotomy. We find recruits with more conservative risk attitudes in two of four measured dimensions are less likely to agree to participate in the study due to these biomedical requirements, suggesting that recruitment among student volunteer populations for fMRI studies and for genetics studies requiring blood as genetic source material may induce a sample selection bias in the domain of risk attitudes. We find that limiting recruitment to individuals who have previously undergone certain types of medical interventions (MRI, computed tomography or surgery) eliminates the sample selection bias in the case of fMRI research and attenuates the bias in the case of genetics research. Furthermore, relying upon buccal cells rather than blood for genetic source material may attenuate sample selection bias. Buccal cell samples can be collected via less invasive oral techniques and have been shown to provide genotyping results that are comparable to blood samples. Author Affiliation: (a) Department of Agricultural, Environmental and Development Economics, Ohio State University, 2120 Fyffe Road, Columbus, OH 43210, USA (b) Departments of Radiology, Neurology and Psychology, Thompson Center for Autism and Neurodevelopmental Disorders, University of Missouri-Columbia, 300 Portland Street, Suite 110, Columbia, MO 65211, USA (c) Department of Pharmacology and Psychiatry, Program in Pharmacogenomics, Ohio State University, 5184B Graves Hall, 333 W Tenth Avenue, Columbus, OH 43210, USA (d) Division of Science and Math, Central Methodist University, 411 CMU Circle, 304E Stedman Hall, Fayette, MO 65248, USA Article History: Received 15 April 2008; Revised 8 July 2008; Accepted 9 July 2008

There are three known high-affinity targets for cocaine: the dopamine transporter (DAT), the serotonin transporter (SERT), and the norepinephrine transporter (NET). Decades of studies support the dopamine (DA) hypothesis that the blockade of DAT and the subsequent increase in extracellular DA primarily mediate cocaine reward and reinforcement. Contrary to expectations, DAT knock-out (DAT-KO) mice and SERT or NET knockout mice still self-administer cocaine and/or display conditioned place preference (CPP) to cocaine, which led to the reevaluation of the DA hypothesis and the proposal of redundant reward pathways. To study the role of DAT in cocaine reward, we have generated a knockin mouse line carrying a functional DAT that is insensitive to cocaine. In these mice, cocaine suppressed locomotor activity, did not elevate extracellular DA in the nucleus accumbens, and did not produce reward as measured by CPP. This result suggests that blockade of DAT is necessary for cocaine reward in mice with a functional DAT. This mouse model is unique in that it is specifically designed to differentiate the role of DAT from the roles of NET and SERT in cocaine-induced biochemical and behavioral effects. addiction | amphetamine | conditioned place preference | knockin