Reversal of tolerance to ethanol associated with the induction of physical dependence on ethanol in the rat.

Three experimental paradigms were employed to investigate the possible relationship between tolerance to and dependence on ethanol in the rat. Groups of rats were exposed to ethanol vapor at various concentrations for different periods of time (e.g., 10 mg/l ethanol vapor for 10 days; 15 mg/l for 0.5 to 10 days; 20 mg/l for up to 12 hours). Tolerance was tested by measuring the concentration of ethanol in the breath at loss of righting reflex of the animal and the withdrawal syndrome was assessed behaviorally. Tolerance developed rapidly and was observed to reverse in association with the development of physical dependence.