Menthol is a significant additive in tobacco products. Mentholated cigarettes account for approximately one- quarter of the total cigarette market. Approximately one-third of current smokers predominantly use mentholated cigarettes. Particularly concerning, young smokers are more likely to initiate smoking with mentholated cigarettes. A fundamental question regarding the mentholation of tobacco products is whether menthol directly enhances the reinforcing effects of nicotine and thus promotes tobacco addiction. Our preliminary studies showed that menthol increased nicotine self-administration at a low dose. This is consistent with other studies that showed that menthol, beyond its peripheral sensory effects, can interact with central nicotinic acetylcholine receptors and change dopamine neurotransmission. Based on these findings, we hypothesize that menthol directly enhances the reinforcing effects of nicotine. To test this hypothesis, this project proposes to systematically examine the effects of menthol on nicotine reinforcement using our established nicotine self-administration paradigm. Menthol will be administered intraperitoneally so the peripheral sensory effects of menthol are eliminated.
In Specific Aim 1, we will test whether menthol promotes the initiation of nicotine self-administration in adolescent rats.
In Specific Aim 2, the enhancing effect of menthol on nicotine reinforcement will be examined in adult rats after the establishment of stable self- administration of nicotine so we can assess whether menthol facilitates the maintenance and progression of nicotine self-administration.
In Specific Aim 3, we will determine whether menthol reinstates nicotine-seeking behavior and promotes nicotine priming and/or nicotine-conditioned cue reinstatement of extinguished nicotine seeking. Finally, we will examine whether menthol changes nicotine-induced release of dopamine in the nucleus accumbens (a terminal region of the brain dopamine reward circuit that originates in the ventral tegmental area). The results of the proposed experiments will provide important information about the contribution of menthol to nicotine reinforcement and tobacco addiction. Thus, this project directly addresses the call of the FDA Center for Tobacco Products: "What are the factors, including menthol and other flavorings that influence the appeal of tobacco products to both users and non-users, including youth and other vulnerable populations? What is the impact of these factors on experimentation, initiation, cessation, switching tobacco products, and multiple uses?" The empirical evidence obtained from this project will support the Center to consider implementing new policies that regulate the addition of menthol in tobacco products, which is one of the Center's first actions mandated by the Family Smoking Prevention and Tobacco Control Act (2009).
A fundamental question with regard to the mentholated tobacco products is whether the presence of menthol facilitates nicotine reinforcement and, as a result, promotes tobacco addiction. This proposal will address the issue using behavioral tests in rodents to examine whether menthol promotes the initiation, maintenance/progression, and relapse of nicotine self-administration without the involvement of the peripheral sensory effects of menthol, and unfold underlying neurochemical mechanisms using intracranial micro dialysis tests. The results collected from this project will present empirical evidence for the FDA Center for Tobacco Products to implement regulatory policies on the use of menthol in tobacco products.
|Liu, Xiu (2015) Enhanced motivation for food reward induced by stress and attenuation by corticotrophin-releasing factor receptor antagonism in rats: implications for overeating and obesity. Psychopharmacology (Berl) 232:2049-60|