Effects of Ethanol and Nicotine Co-Administration on Risky Choice in Rats

Individuals often engage in the comorbid use of alcohol (ethanol) and nicotine, leading to further-escalated health consequences than the use of either drug in isolation. Given the poor health outcomes resulting from the combined administration of ethanol and nicotine, some of which may be due to increased risky choice, more basic research is needed to better characterize drug/dose interactions on risky choice. Probability-discounting procedures involve a series of discrete choices between a smaller, certain reinforcer (i.e., a safer choice) and a larger, increasingly uncertain reinforcer (i.e., a riskier choice). Probability-discounting procedures allow for the assessment of risky choice across studies and facilitate the understanding of drug-related increases in risky choice. The present study investigated effects of acute ethanol alone (Experiment 1) and in combination with nicotine (Experiment 2) using eight Sprague-Dawley rats. Effects of ethanol and nicotine on risky choice were evaluated using both visual analysis and repeated measures ANOVAs. Results of Experiment 1 indicate increases in risky choice and decreases in aversion to losses following the administration of ethanol alone (2.0 and 3.0 g/kg) compared to vehicle. Results of Experiment 2 indicate increases in risky choice on one dependent measure (h; rate of discounting) following the administration of nicotine alone (0.3 mg/kg) compared to vehicle. Further, there were increases in risky choice on one dependent measure (percent of choices for the larger reinforcer) following the administration of ethanol (2.0 g/kg) with nicotine (1.0 mg/kg) compared to the same dose of ethanol with a lower dose of nicotine (0.3 mg/kg). Factors such as the concentration and route of administration of ethanol, as well as the presence of sucrose in the vehicle for ethanol delivery, may have impacted effects of ethanol in the present study. Future directions include assessing effects of administering ethanol in different doses and concentrations, as well as with differing routes of administration