Flavors Enhance Nicotine Vapor Self-administration in Male Mice

Although the use of combustible cigarettes has decreased in many urban regions of America, the use of electronic nicotine delivery systems (ENDS) has dramatically increased. ENDS, or electronic cigarettes (e-cigarettes), differ from combustible cigarettes given that there are no restrictions on flavorant additives in e-liquids. With 95% of ENDS users vaping flavored e-liquids, it is critical to understand how flavors alter vaping-related behaviors. We have previously shown that menthol and green apple flavors enhance nicotine reward-related behavior in a mouse model and in the present study have investigated how menthol and green apple flavors alter e-Vape self-administration behavior in male mice.

Adult C57/BL6J male mice were used in vapor-inhalation self-administration assays. Mice were assigned vaping e-liquids (6 mg/mL nicotine with or without menthol or green apple flavor) to escalate on a fixed-ratio 1 (FR1) schedule in daily 3-hour sessions to examine initiation-related behaviors. Following escalation, mice were transitioned to a FR3 and progressive ratio schedules in 3-hour sessions to examine reinforcement-related behaviors.

Here we observed that male mice exhibited increased rates of self-administration escalation on a FR1 schedule when assigned to flavored e-liquids. Upon transition to FR3, mice continued to exhibit enhanced levels of reinforcement with flavored e-liquids. We also observed that mice self-administer zero-nicotine green apple flavored e-liquids.

These data provide additional evidence that ENDS flavors enhance vaping-related initiation and reinforcement-related behavior and promote the need to continue investigating the role ENDS flavors play in vaping-related behaviors.

There has been much discussion recently regarding the impact of flavors on vaping-related behavior. Our study here shows that flavors significantly enhance the acquisition and reinforcement of vaping-related behavior. This suggests that flavors in electronic nicotine delivery systems significantly increase the risk of addiction-related behaviors among users of vaping products.