Effects of isolated tobacco alkaloids and tobacco products on deprivation-induced food intake and meal patterns in rats

Abstract

The ability of smoking to reduce body weight serves as motivation for continued smoking. It is unclear to what extent non-nicotine constituents in cigarettes are contributing to the weight-reducing effect of smoking. The purpose of the current study was to examine the effects of nicotine and four minor tobacco alkaloids (nornicotine, cotinine, anatabine, and anabasine) on food intake, one of the key regulators of body weight. In addition, a smokeless tobacco extract (STE) and e-cigarette (EC) refill liquid were used to model the effects of actual tobacco product exposure on food intake. Male Holztman rats were trained to lever press for food pellets during daily 2h sessions in operant chambers. In Experiment 1, the effects of subcutaneous injections of saline, nicotine (0.25-1.00mg/kg), nornicotine (0.50-6.00mg/kg), cotinine (1.00-100.00mg/kg), anatabine (0.25-3.00mg/kg), and anabasine (0.50-4.00mg/kg) were assessed. In Experiment 2, rats from Experiment 1 were used to examine the effects of nicotine, STE, and EC liquid. All alkaloids, except cotinine, produced a dose-dependent reduction in overall food intake. The highest doses of all drugs significantly reduced latency and response rate to obtain the first pellet. At some doses, nicotine, anatabine, and nornicotine reduced food intake within the first 45min without compensatory increases in intake later in the session. STE and EC liquid produced dose dependent decreases in food intake similar to nicotine alone. These data suggest that minor tobacco alkaloids have appetite suppressant effects and warrant further investigation into their effects on body weight, energy intake, and energy expenditure under free-feeding conditions. However, findings with STE and EC liquid suggest that nicotine is the primary constituent in these products to affect food intake, whereas levels of minor alkaloids in these products may be too low to influence food intake.

Keywords: E-cigarettes; Food intake; Meal patterns; Minor tobacco alkaloids; Nicotine; Smokeless tobacco.