Parallel development of ethanol tolerance and operant compensatory behaviors in rats.

This experiment was designed to detect compensatory learning that has been suggested to occur during the course of tolerance development to ethanol's effects on operant performance. The effects of presession ethanol injections on the development of tolerance to ethanol's effects on operant performance in an afternoon Fixed-Ratio (FR) task was assessed in rats that were concurrently performing in a morning DRL task. Only presession saline injections were administered for the DRL task. A cumulative dosing procedure was used to establish initial and postethanol exposure dose-effect curves for both tasks. Daily presession ethanol administration produced a 3-fold shift-to-the-right in the dose-effect curve for FR-task performance. No changes were evident in the FR-task performance of controls that received daily saline injections. However, during the period of daily ethanol injections and during subsequent cumulative dose tests, the ethanol, but not the control, group displayed dose-related increases in total DRL-task responses relative to baseline. These DRL data were interpreted as reflecting the development of rate-increasing behaviors that compensated for and contributed to the tolerance of ethanol's rate-decreasing effects on FR-task performance.