Ethanol self-administration in ALKO rats: II. Effects of selection and fixed-ratio size.

The ethanol-reinforced behavior of ALKO Alcohol Accepting (AA) rats was studied as a function of fixed-ratio (FR) size (1, 2, 4, 8 and 16) across several ethanol concentrations (8, 16 and 32% w/v). A comparison was also made with ethanol-reinforced behavior of Sprague-Dawley (SD) rats. Ethanol, previously shown to serve as a reinforcer in AA and SD rats, maintained responding in these animals under conditions of intermittent reinforcement. SD rats exhibited higher response rates than AA rats to obtain 8% ethanol concentrations as fixed-ratio size was varied in these experiments. These results confirm that, for AA rats, the selection for preference in a two-bottle choice situation did not include the selection for those biological factors which maximize ethanol-reinforced behavior under conditions of intermittent reinforcement. These experiments suggest the existence of distinct, biologically influenced components of ethanol drinking behavior, and have demonstrated several similarities as well as differences between two-bottle choice preference tests and operant studies of ethanol-reinforced behavior.