Unequal interactions between alcohol and nicotine co-consumption: Suppression and enhancement of concurrent drug intake

Rationale Alcohol and nicotine addiction are prevalent conditions that co-occur. Despite the prevalence of co-use, factors that influence the suppression and enhancement of concurrent alcohol and nicotine intake are largely unknown. Objectives Our goals were to assess how nicotine abstinence and availability influenced concurrent alcohol consumption, and to determine the impact of quinine adulteration of alcohol on aversion resistant alcohol consumption and concurrent nicotine consumption. Methods Male and female C57BL/6J mice voluntarily consumed unsweetened alcohol, nicotine and water in a chronic 3-bottle choice procedure. In Experiment 1, nicotine access was removed for 1 week and re-introduced the following week, while the alcohol and water bottles remained available at all times. In Experiment 2, quinine (100-1000 μM) was added to the 20% alcohol bottle, while the nicotine and water bottles remained unaltered. Results In Experiment 1, we found that alcohol consumption and preference were unaffected by the presence or absence of nicotine access in both male and female mice. In Experiment 2a, we found that quinine temporarily suppressed alcohol intake and enhanced concurrent nicotine, but not water, preference in both male and female mice. In Experiment 2b, chronic quinine suppression of alcohol intake increased nicotine consumption and preference in female mice without affecting water preference, whereas it increased water and nicotine preference in male mice. Conclusions Quinine suppression of alcohol consumption enhanced the preference for concurrent nicotine preference in male and female mice, suggesting that mice compensate for the quinine adulteration of alcohol by increasing their nicotine preference.