Electronic Cigarettes, Adolescents, and Changes in Neurobiology

The goal of this application is to provide behavioral data that will inform the regulatory authority of the Food and Drug Administration (FDA) Center for Tobacco Products (CTP). Nicotine is the primary addictive compo-nent in tobacco products but we are now learning that tobacco flavorants play an important role as well. Menthol, the most popular tobacco flavorant, has been found to reduce long-term cessation rates (Ahijevych and Garrett, 2010; D'Silva et al., 2012) and both the FDA and World Health Organization (WHO) agree menthol poses significant public health concerns (Administration, 2012; WHO, 2016). Our research has played an im-portant role in the study of menthol and smoking behavior as we have shown that menthol enhances nicotine-related reward through dopamine neurons (Henderson et al., 2016; Henderson et al., 2017). With the growing popularity of electronic nicotine delivery systems (ENDS) that offer hundreds of fla-vors, there is a critical need to understand how flavors alter addiction and smoking behavior. This is especially true given the rising rates of ENDS initiation among young Americans and the fact that young smokers pre-dominantly use flavors with their ENDS (CDC, 2016; Villanti et al., 2016). This rapid increase in youth smoking points to a growing concern about a new generation of lifelong smokers (D'Silva et al., 2012). Our goal is to conduct scientific investigations that align with two Scientific Interest Areas of the FDA-CTP: •Addiction – This application will enhance the understanding of how tobacco flavors affect addictionand abuse liability. It will study the impact of changes in flavors (transitions from flavored to non-flavored products) on dependence and use patterns. It will study the correlation of ENDS use behaviorswith pharmacodynamic effects of nicotine and tobacco flavors that are delivered by ENDS. This will generate data that can be applied to examining how flavored ENDS impact successful quit attempts. This application will enhance the understanding of behaviors related to changes in tobaccoflavors. We will study the impact of flavors on tobacco use behaviors: initiation, transition to non-flavored products, and cessation. We will address these Scientific Interest Areas with four aims: Aim 1: Determining tobacco flavors’ impact on smoking initiation behaviors Following our preliminary showing that menthol and green apple flavor enhance nicotine reward, our working hypothesis is that flavors increase smoking initiation behaviors. We will use e-Vape self-administration with mice to examine how flavors alter the rate of smoking initiation behavior. Aim 2: Determining the impact of transitioning from flavored to non-flavored ENDS on addiction and abuse liability Our working hypothesis is that transitioning to non-flavored products may reduce addiction and abuse liability. Similar to Aim 1 we will use e-Vape self-administration test for changes in self-administration following a transi-tion from flavored to non-flavored e-juice. Aim 3a: Linking ENDS behavior with pharmacodynamics: midbrain neuron function Our working hypothesis is that nicotine and tobacco flavor initiated changes in dopamine and GABA neuron function (observed via electrophysiology) will provide a pharmacodynamic measure (in addition to Aim 3) that will correlate changes in smoking initiation and addiction by nicotine and tobacco flavorants (Aims 1 and 2) to the pharmacodynamics of nAChR function on these target neurons. Aim 3b: Linking ENDS behavior with midbrain neuron firing in human smokers. Using electrophysiol-ogy we will observe changes in firing frequency of substantia nigra neurons in smokers undergoing deep brain stimulation. Human subjects puff on a SREC (control, nicotine, or flavored) and firing frequency will be record-ed before, during, and after, puff intervals. Aim 4: Linking ENDS behavior with pharmacodynamics: nAChR upregulation Our working hypothesis is that nAChR upregulation in midbrain dopamine and GABA neurons that is triggered by nicotine and tobacco flavors delivered by ENDS will provide a measure that will correlate smoking initiation and addiction (Aims 1 and 2) to the pharmacodynamics of nAChR upregulation by nicotine and tobacco fla-vors. Regarding outcomes of this R01 proposal, we believe this project will provide validation of the harm ENDS flavors pose to public health. We believe that the outcome of this project will be basic science that supports the FDA’s claim that flavors pose a risk to public health, that they should be deemed a harmful and potentially harmful constituents (HPHCs) of ENDS, and that they need to be restricted. The rationale for this comes from our preliminary data, which is discussed further in the following Research Strategy section. Richards SOW:Dr. Richards is an expert in fluorescence microscopy, single-molecule spectroscopy, and membrane receptor biophysics. He has extensive experience with the proposed receptor trafficking studies.