RESUMO
Nicotine self-administration in rats is the most widely used animal model of tobacco dependence. There is increasing evidence, however, that non-nicotinic constituents in smoke contribute to addiction and that different tobacco products contain varying levels of these constituents. The present study firstly sought to compare self-administration of pure nicotine to tobacco particulate matter (TPM) to determine if there were differences in reward-efficacy attributable to the non-nicotine constituents. Secondly, cigarette and roll-your-own (RYO) TPM groups were included and compared to determine whether different formulations of non-nicotinic constituents could impact reward. Briefly, male Sprague Dawley rats were implanted with indwelling jugular catheters for self-administration (n = 76). The reinforcing efficacy of infusions of nicotine (0.0 or 30.0 µg/kg/infusion) versus cigarette/RYO TPM (with matched nicotine content) was determined using spontaneous acquisition of self-administration on a fixed ratio schedule. The progressive ratio schedule was then employed to determine the motivation to receive each drug and within-subject dose-response curves were also produced (7.5, 15.0, 30.0 and 60.0 µg/kg/infusion nicotine). The main finding was that the RYO TPM was more reinforcing and produced a different profile of reward-related behaviour compared with both the nicotine and the cigarette TPM groups. The conclusions were that non-nicotinic components have a role in tobacco dependence and that some tobacco products could have higher abuse liability, irrespective of nicotine levels.
