Flavor-specific enhancement of electronic cigarette liquid consumption and preference in mice

Abstract

<jats:title>Abstract</jats:title><jats:sec><jats:title>Background</jats:title><jats:p>The use of electronic cigarettes has increased over the past decade. To determine how the abuse liability of electronic cigarette liquids (e-liquids) differs from nicotine alone, and to determine the impact of flavor, we compared nicotine-containing fruit- and tobacco-flavored e-liquids, and their nicotine-free versions, to nicotine alone in mouse models of oral consumption, reward and aversion.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>Adult male C57BL/6J mice voluntarily consumed oral nicotine, equivalent nicotine concentrations of fruit- and tobacco-flavored e-liquid, and equivalent dilutions of the nicotine-free versions in 2-bottle choice tests. Conditioned place preference and place aversion were assessed with peripherally administered e-liquids or nicotine. Serum nicotine and cotinine levels were measured after subcutaneous injections of e-liquid or nicotine.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>Mice showed higher consumption and preference for the fruit-flavored e-liquid compared with nicotine alone. This increase was not due to the flavor itself as consumption of the nicotine-free fruit-flavored e-liquid was not elevated until the highest concentration tested. The increased consumption and preference were not observed with the tobacco-flavored e-liquid. The conditioned place preference, place aversion and nicotine pharmacokinetics of the fruit-flavored e-liquid were not significantly different from nicotine alone.</jats:p></jats:sec><jats:sec><jats:title>Conclusions</jats:title><jats:p>Our data suggest that fruit, but not tobacco flavor, increased the oral consumption of e-liquid compared with nicotine alone. Moreover, this enhancement was not due to increased consumption of the flavor itself, altered rewarding or aversive properties after peripheral administration, or altered pharmacokinetics. This flavor-specific enhancement suggests that some flavors may lead to higher nicotine intake and increased use of e-liquids compared with nicotine alone.</jats:p></jats:sec><jats:sec><jats:title>Highlights</jats:title><jats:p><jats:list list-type="bullet"><jats:list-item><jats:p>Fruit flavor, but not tobacco flavor, enhances e-liquid consumption and preference</jats:p></jats:list-item><jats:list-item><jats:p>The nicotine-free flavored e-liquid is not preferred over nicotine alone</jats:p></jats:list-item><jats:list-item><jats:p>Conditioning rewarding and aversive effects are equal between nicotine and e-liquid</jats:p></jats:list-item></jats:list></jats:p></jats:sec>

Sex differences in the impact of electronic nicotine vapor on corticotropin-releasing factor receptor 1 neurons in the mouse ventral tegmental area

“…ENDS use has increased dramatically, however, the effects of nicotine vapor on brain reward and stress circuitry remain unclear. Previous studies have used alternative forms of nicotine delivery like subcutaneous minipumps 24,36 , drinking water 37,38 , intraperitoneal [39][40][41] , or intravenous 4,5 injections. This study used a nicotine vapor inhalation model that allows nicotine to reach the brain on a timescale similar to nicotine from cigarettes 42 , which is a primary determinant of nicotine reinforcement 43 .…”