The rodent electronic nicotine delivery system: Apparatus for voluntary nose-only e-cigarette aerosol inhalation

Tobacco use is the leading cause of death globally and in the U.S. After decades of decline, driven by decreases in combusted tobacco use, nicotine product use has increased due to Electronic Nicotine Delivery Systems (ENDS), also known as e-cigarettes or vapes. Preclinical models of nicotine self-administration can serve as important lodestars in the search for effective intervention and prevention tactics. Current variants of the task have substantial limitations, however. Therefore, we created the Rodent Electronic Nicotine Delivery System (RENDS), a novel low-cost non-proprietary snout-only preclinical model of self-administration of nicotine aerosol. We validated the RENDS using two techniques. First, we measured fine particulate matter (2.5 microns or less in diameter), generated by e-cigarettes, and showed that levels in the chamber were similar to room air when RENDS was in operation, confirming that nicotine aerosol is sequestered in the nose port. We also demonstrated that rats robustly self-administer flavored nicotine aerosol, resulting in high blood levels of cotinine (the major nicotine metabolite) and spontaneous somatic withdrawal symptoms. Thus, we provide strong validation of the operation and function of the RENDS, opening the door to an open-source preclinical aerosol model of nicotine self-administration that is far less costly. Four existing operant chambers can be retrofitted with the RENDS for under $1,300. All RENDS diagrams and plans for custom designed components can be found freely on our open science framework site (OSF; https://osf.io/x2pqf/?view_only=775b55435b8e428f98e6da384ef7889d).