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

Introduction:
This text provides a summary of a scientific study examining the abuse liability of electronic cigarettes (ECs) in young adults. The study investigates the potential for nicotine contained in ECs to enhance the reinforcing effects of non-drug rewards, a phenomenon known as reinforcement-enhancement. The study also examines the relationship between nicotine-induced reinforcement enhancement and hedonic and subjective effects of nicotine.

Key Points:

* The study included three groups of young adult never-users of nicotine products.
* The groups received either placebo ECs, ECs with 6 mg of nicotine, or ECs with 12 mg of nicotine.
* The participants completed up to eight experimental sessions, with the first two sessions serving as a baseline.
* The study measured the participants' progressive-ratio (PR) schedule breakpoints and videogame-play durations.
* The results showed that nicotine consumption increased PR schedule breakpoints and videogame-play durations compared to placebo.
* The study also found that nicotine consumption was associated with greater subjective evaluation of the enjoyment of the videogame, but was unrelated to enjoyment of the EC device.
* No evidence was found that nicotine elevated anhedonia or withdrawal symptoms in the timeframe of the study.

Main Message:
The study provides 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. The results suggest that the mechanism underlying the transition from first use to dependence cannot be fully described by nicotine as a primary reinforcer or by nicotine's activation of opioid receptors to produce a strong hedonic response. an understanding of the stimuli and contingencies that initiate and maintain nicotine use is most complete when the role of nicotine is examined as both a primary-reinforcing agent and a reinforcer enhancer. Reinforcement enhancement may be related to brain-reward sensitization via nicotine, and the aftermath of nicotine dosing includes the desensitization of mesolimbic-dopamine reward pathways, which may cause the devaluation of other available reinforcers. The National Institutes of health funded this study to examine both nicotine enhancement and nicotine-induced devaluation of non-drug reinforcement in a group of young never-users. The study found that nicotine enhancement occurred in a dose-dependent manner, and the influence of repeated exposure to nicotine to enhance videogaming in young adults was expected to intensify with repeated experience. The possible effect of nicotine-induced reinforcement devaluation will be reported in a future manuscript.

Kirshenbaum aP, hughes JR. Reinforcement enhancement by nicotine: a novel abuse-liability assessment of e-cigarettes in young adults. Experimental and clinical psychopharmacology. 2022;30(6):959-972. doi:10.1037/pha0000496