[1] Univ Calif San Francisco, Dept Med, Med Serv, Div Clin Pharmacol & Expt Therapeut, San Francisco, CA 94143 USA
[2] Univ Calif San Francisco, Dept Bioengn & Therapeut Sci, San Francisco, CA 94143 USA
[3] Univ Calif San Francisco, Ctr Tobacco Control Res & Educ, San Francisco, CA 94143 USA
[4] Univ Pittsburgh, Dept Psychol, Pittsburgh, PA 15260 USA
[5] Univ Minnesota, Tobacco Res Programs, Minneapolis, MN USA
[6] Univ Minnesota, Dept Psychiat, Minneapolis, MN 55455 USA