Rapid Tolerance to Ethanol in Adolescent Rats: Expression Through Physiological and Behavioral Parameters

REYNA CE; DZIULA CE; MOLINA JC; GODOY JC

Santa Barbara, California

Congreso; 28th Annual Scientific Meeting of the Research Society on Alcoholism; 2005

Research Society on Alcoholism

Several studies have indicated that the development of rapid tolerance to ethanol (EtOH) differs according to the mode of expression under analysis. In the present study we analyzed the possibility of development of rapid tolerance to EtOH through the use of thermoregulatory responses and through motor behaviors elicited by the presence of novel objects. Adolescent rats were administered on Day 1 (D1) with saline or with a 2.25 g/kg i.g. EtOH dose. On Day 2 (D2) juveniles were subjected to the same or the alternative treatment corresponding to the previous day. Hence, four groups were evaluated: Saline-Saline, Saline-ETOH, ETOH-Saline or ETOH-ETOH. On each day, baseline motor activities in an open-field as well as rectal temperature were recorded. Following saline or ethanol administrations (post-administration time: 30, 60 and 120 min) thermal and motor responsiveness were again evaluated. In each open-field test, a novel object was placed in the peripheral section of the apparatus. As could be expected, EtOH induced marked hypothermia during the first day of treatment. This drug-related thermoregulatory disruption was markedly attenuated during the second day of evaluation in juveniles that had prior exposure to EtOH (group EtOH-EtOH). Surprisingly, drug treatment failed to exert significant effects upon different motor parameters that allude to juvenile exploratory patterns elicited by novel objects. Nevertheless, there was a clear impact of the drug upon locomotive activity, particularly during the second day of testing. Rats that were administered with saline during the first day and with EtOH during the second day (Saline-EtOH), showed heightened locomotion scores during D2 when compared with groups Saline-Saline or EtOH-Saline. In turn, group EtOH-EtOH exhibited intermediate scores relative to the remaining groups. These results argue in favor of the acquisition of rapid tolerance to EtOH in adolescent rats when this functional process is evaluate through thermoregulatory responsiveness. The results also suggest that an analogous process can be detected through non-associative learning process that regulates motor expression in a novel environment.