THE DEVELOPMENT OF TOLERANCE TO ATAXIA AND TO DIURESIS INDUCED BY ETHANOL IN RATS IS NOT SIMULTANEOUS

The present study was conducted to determine whether behaviorally accelerated development of tolerance to the disruptive effects of ethanol on rotarod performance paralleled the development of tolerance to ethanol-induced diuresis and to determine the effect of pre- and post-training ethanol administration on the development of tolerance to both of these effects. Male Wistar rats were treated with ethanol (2 g kg-1 day-1, ip) over a period of 5 weeks under one of the following schemes: ethanol injections before training (pre-training ethanol group) or after training (post-training ethanol group). Control animals received 0.9% NaCl, ip, after training. The effect of ethanol on diuresis was assessed once a week. Data are reported as means +/- SEM of 6 animals. Significant tolerance to the uncoordinating effect of ethanol was detected from the 17th day of treatment onwards in animals of the pre-training ethanol group (2nd day = 1.7 +/- 0.6 s vs 17th day = 39.0 +/- 8.1 s, Student t-test for related samples) but was not observed in animals of the post-training ethanol group until 34 days of treatment (pre-training ethanol group = 56.1 +/- 8.5 s; post-training ethanol group = 29.8 +/- 9.6 s vs control group = 12.6 +/- 7.6 s, Newman-Keuls test). In contrast, the development of tolerance to the diuretic effect of ethanol was similar in both groups and appeared after 4 weeks of treatment (pre-training ethanol group: 28th day = 1.9 +/- 0.7 ml vs 1st day = 4.0 +/- 0.5 ml, Student t-test for related samples; post-training ethanol group: 28th day = 1.0 +/- 0.6 ml vs 1st day = 3.1 +/- 0.3 ml, Student t-test for related samples). These data suggest that tolerance to the motor incapacitating effect of ethanol does not affect the time course of tolerance to ethanol-induced diuresis and thus, the two processes involve independent mechanisms. Moreover, the data confirm that tolerance to the disruptive effect of ethanol on rotarod performance can be influenced by the scheme of training.