In humans, opioid receptor antagonist naloxone may reduce the relative reinforcing effects of nicotine, thus it has been used as a smoking cessation drug [9-11]. Lerman and colleagues show that a variant in OPRM1 may predict the treatment responses to clinical nicotine replacement therapy. Smokers who have the Asp40 variant in the OPRM1 gene are likely to have a favorable response to the treatment [12]. Interestingly, the OPRM1 gene is located at 6q24-25, about 4 million basepairs from a suggestive linkage peak of nicotine dependence [13]. All these suggest that the OPRM1 is an attractive candidate gene that may influence the smoking behavior in humans.
