Reinforcement enhancement by nicotine: A novel abuse-liability assessment of e-cigarettes in young adults.

Abstract

Nicotine can act as a primary positive reinforcer, and as negative reinforcer to relieve withdrawal; we tested whether it can also enhance the reinforcing efficacy of non-drug reinforcers. Young-adult never-users were delivered nicotine via e-cigarette, and a videogame reinforcer was used to test nicotine enhancement. Three dose groups were tested (placebo-only, 6 or 12-mg nicotine), and participants returned to the lab for several sessions over the course of 1 month. Those in the two nicotine-dose groups received placebo on some occasions and nicotine on others; nicotine enhancement of the videogame reinforcer was assessed in a within-subjects fashion by comparing each of the two nicotine groups' dedicated nicotine dose to placebo. In the placebo-only group, progressive-ratio (PR) schedule breakpoints did not alter as a function of videogame exposure, suggesting that the videogame retained its basic-reinforcing properties throughout the study. For the two groups that received nicotine, both doses of nicotine increased PR-schedule breakpoints for the videogame reinforcer relative to the placebo condition. Although nicotine was associated with greater subjective evaluation of the enjoyment of the videogame, it was unrelated to the enjoyment of the e-cigarette device. No evidence was found that nicotine elevated either anhedonia or withdrawal symptoms in the timeframe of the study. The results provide initial evidence that nicotine enhancement, via electronic cigarettes, occurs in non-frequent users of nicotine products and may be a reason they can develop nicotine dependence in the absence of withdrawal and direct effects of nicotine. Public Significance StatementOne reason e-cigarettes may have abuse liability is because the nicotine in them increases the reinforcing effects of non-drug rewards; these effects of nicotine are known as reinforcement-enhancement. We examined how nicotine contained in e-cigarettes changes video-game reinforcement in young-adult non-users, and how hedonic and subjective effects of nicotine are related to nicotine-induced reinforcement enhancement.

A novel abuse liability assessment of e-cigarettes in young adults ii: Reinforcement enhancement and follow-up assessment.

“…This was accomplished by delivering two different doses of nicotine (6 or 12 mg) in a repeated fashion and witnessing changes in the efficacy of a video game reinforcer relative to a placebo (0 mg). The results presented here demonstrate that 6 and 12 mg ENDS enhance performance measures of reinforcer efficacy (PR break point and video game play durations, see Table 2) and are consistent with our earlier report (A. P. Kirshenbaum & Hughes, 2022).…”

“…Experimental evaluation of reinforcement enhancement by nicotine in humans has not followed the same repeated dosing design. In our previous study (A. P. Kirshenbaum & Hughes, 2022), ENDS enhanced the reinforcer efficacy of a video game, and results were published at the study midpoint to provide data on the immediate short-term effect of nicotine.…”

Reliability and validity of a transdiagnostic measure of reward valuation effort.

“…Thus, the game itself is not presented as the reward, and the apples represent a secondary reinforcer. Building off the “apple picker” game, Kirshenbaum and Hughes (2021) recently used immediate consumption of game play as a primary reinforcer in humans. However, after pressing a key to earn access to the game in a PR task, participants then received unlimited access to game play.…”

“…That is, individual differences in the extent that reward consumption brings about a state of satisfaction, completion or consummation leading to spontaneous termination of consumption. Finally, Kirshenbaum and Hughes (2021) did not report data on reliability or validity for their tasks.…”

“…leading to spontaneous termination of consumption. Finally, Kirshenbaum and Hughes (2021) did not report data on reliability or validity for their tasks.…”