Sensitivity and tolerance to the motor impairing effects of moderate doses of ethanol

The present study assessed sensitivity and the development of tolerance to the motor impairing effects of moderate doses of ethanol, using an oscillating bar task. Adult male Wistar rats were trained for 5 consecutive days to stay on the oscillating bar for 120 s to avoid a 0.5-mA foot shock. On the 5 consecutive test days, animals were injected once a day with ethanol (ip: 1.0, 1.25, or 1.5 g/kg) and tested at 15 min intervals until recovery to the 120 s criterion. On test day 1, rats in the 1.5 g/kg group took significantly longer to recover (81+/-9 min; mean+/-S.E.M.) than did animals in the 1.25 (49+/-9 min) and 1.0 (29+/-5 min) g/kg groups. Tolerance developed to all doses by test day 3, with the 1.5, 1.25, and 1.0 g/kg groups reaching criterion in significantly shorter times (42+/-8, 31+/-5, and 18+/-2 min, respectively), as compared to test day 1. BACs associated with recovery time on test day 3, for the 1.5 g/kg group, were significantly higher than the BACs associated with recovery time on test day 1. The data suggest that the oscillating bar task can be used to measure the acute ataxic effects of ethanol, across a narrow range of moderate ethanol doses, and, as well, the development of tolerance to the motor impairing effects of these ethanol doses.