Operant self-administration of sweetened versus unsweetened ethanol: effects on blood alcohol levels

Sweeteners are often added to ethanol solutions to increase ethanol intake. However, literature on studies that use human subjects and laboratory animals suggests that sucrose, other sugars, and carbohydrate-rich foods alter ethanol absorption and metabolism, which leads to lower blood alcohol levels (BAL) relative to ethanol absorbed alone. This experiment was designed to test whether the addition of the nutritive sweetener sucrose, or the nonnutritive sweetener saccharin, to a 10% ethanol solution, self-administered in an oral operant paradigm, affected BAL in rats relative to self-administration of an unsweetened 10% ethanol solution.

All rats were trained to lever press for ethanol by use of a saccharin fading procedure. Half of the rats then received 30-min sessions in which ethanol + 2% sucrose and water were available and were alternated daily with sessions in which ethanol + 0.2% saccharin and water were available. The other half of the rats went on to receive daily sessions of unsweetened ethanol and water. BAL were taken after these standard daily sessions as well as after a 1-week period of alcohol deprivation (to enhance ethanol intake).

Rats responded for more ethanol + sucrose than unsweetened ethanol, but had lower BAL per gram ethanol consumed in both the baseline test and alcohol deprivation effect test. No effect of saccharin on BAL was detected. An additional experiment that examined the effects of four concentrations of both sucrose and saccharin on self-administration of ethanol and BAL showed that, whereas rats consumed more ethanol + sucrose than ethanol + saccharin, BAL were significantly lower per gram ethanol consumed in the sucrose group.

These results confirm previous reports and suggest that the addition of sucrose to an ethanol solution can result in lower BAL relative to unsweetened ethanol in an oral operant self-administration paradigm.