IV nicotine self-administration (IVNSA) is an animal model of the reinforcing effects of nicotine that has been widely used to explore issues related to nicotine and tobacco dependence. In contrast, research on the abuse liability of ENDS and associated e-liquids is relatively sparse. There are currently no validated preclinical models of inhaled nicotine aerosol (e.g., volitional ENDS use). There is also limited information available on the role of flavor additives and their potential interaction with nicotine on ENDS product use and abuse liability. The proposed research will address the FDA CTP scientific interest areas of addiction and behavior. The premise of this proposal is that flavor additives in nicotine and tobacco products are conditioned reinforcers (CRs), and regulation of flavors through policy will impact abuse liability of ENDS. Aerosol nicotine self-administration (ANSA) is an important goal for preclinical research because the pharmacology and chemosensory effects of inhaled nicotine are more comparable to human ENDs use. Development of ANSA will complement IVNSA studies exploring the impact of removing flavors from ENDS products. The goal of the proposed studies is to examine the role of e-liquid flavors in abuse liability of ENDS, and investigate how a policy change to regulate flavors affects ENDS abuse liability. Flavors are ENDS characteristics that are within the scope of FDA?s regulatory authority. In the proposed studies, rats will be exposed to nicotine, with or without flavor, for self- administration, and comparison of these conditions will model a policy change to regulate flavors in e-liquids. The results of this project will provide key information on the reinforcing effects of oral and aerosolized flavors, and whether they interact with nicotine to promote nicotine use and abuse.
Aim 1 will extend our previous IVNSA findings with flavor CRs. After a popular ENDS flavor (blueberry) is established as a CR, male and female rats will self-administer IV nicotine with oral delivery of 1) flavor CRs, 2) neutral flavor, or 3) no flavor. Behavioral testing will include a progressive ratio (PR) schedule of reinforcement to measure motivation. Flavor will subsequently be removed to model a policy change to regulate flavors in e-liquids.
Aim 2 will extend our IVNSA methods to the more translationally relevant ANSA. Methods will be similar to Aim 1 except that during self-administration, nicotine and flavors will be self-administered via aerosol. Male and female rats will self-administer aerosolized nicotine plus 1) flavor CRs, 2) unconditioned flavor, or 3) no flavor. In summary, these studies will employ the complementary methods of IVNSA and ANSA to investigate the role of e-liquid flavors in abuse liability of e-cigarettes, and address the scientific interest areas of addiction and behavior. Results will provide novel and translationally relevant data on the potential impact of regulation of flavor additives in ENDS, which may affect initiation of nicotine use, and contribute to dependence.
Nicotine products, including e-cigarettes, are some of the most highly addictive substances, and chronic use of nicotine products has led to considerable public health concerns. The goal of the proposed studies is to examine the role of e-liquid flavors in abuse liability of e-cigarettes, and investigate how a policy change to regulate flavors affects e-cigarette abuse liability. This project will provide key information on whether flavors interact with nicotine to promote nicotine use and abuse, which will inform tobacco and e-cigarette policy.
