RESUMO
In previous study, we demonstrated that ethanol preexposure may increase ethanol consumption in both adolescent and adult mice, in a two-bottle choice model. We now questioned if ethanol exposure during adolescence results in changes of consumption pattern using a three-bottle choice procedure, considering drinking-in-the-dark and alcohol deprivation effect as strategies for ethanol consumption escalation. We also analyzed aldehyde dehydrogenase (ALDH) activity as a measurement of ethanol metabolism. Adolescent and adult Swiss mice were treated with saline (SAL) or 2.0 g/kg ethanol (EtOH) during 15 days (groups: Adolescent-SAL, Adolescent-EtOH, Adult-SAL and Adult-EtOH). Five days after the last injection, mice were exposed to the three-bottle choice protocol using sucrose fading procedure (4% + sucrose vs. 8%-15% ethanol + sucrose vs. water + sucrose) for 2 h during the dark phase. Sucrose was faded out from 8% to 0%. The protocol was composed of a 6-week acquisition period, followed by four withdrawals and reexposures. Both adolescent and adult mice exhibited ethanol behavioral sensitization, although the magnitude of sensitization in adolescents was lower than in adults. Adolescent-EtOH displayed an escalation of 4% ethanol consumption during acquisition that was not observed in Adult-EtOH. Moreover, Adult-EtOH consumed less 4% ethanol throughout all the experiment and less 15% ethanol in the last reexposure period than Adolescent-EtOH. ALDH activity varied with age, in which older mice showed higher ALDH than younger ones. Ethanol pretreatment or the pattern of consumption did not have influence on ALDH activity. Our data suggest that ethanol pretreatment during adolescence but not adulthood may influence the pattern of ethanol consumption toward an escalation in ethanol consumption at low dose, without exerting an impact on ALDH activity.
RESUMO
BACKGROUND: Increasing evidence shows that excessive alcohol consumption during adolescence increases vulnerability to alcohol use disorders in adulthood. The aim of this study was to examine differences between adolescent and adult C57BL/6J mice in drinking behavior and blood ethanol (EtOH) concentrations (BECs) after chronic EtOH exposure and withdrawal. METHODS: Male adolescent (PND = 28 to 30) and adult (PND = 70) C57BL/6J mice were allowed to consume EtOH in a 2-bottle choice paradigm (15% EtOH vs. water) for 3 weeks (Baseline drinking, Test 1, and Test 2), which were interspersed with 2 cycles (Cycles I and II) of chronic EtOH vapor or air inhalation (16 hours) and withdrawal (8 hours). BECs were determined during both cycles. RESULTS: Chronic EtOH exposure led to increased EtOH intake during Test 1 and Test 2 in both adolescent and adult mice compared with air-exposed controls, and no differences between age groups were observed. During Cycle I adult mice showed higher BECs compared with adolescents. During Cycle II, BECs were lower in adult mice as compared to Cycle I, and BECs in adolescent mice did not change between the 2 cycles. CONCLUSIONS: Chronic EtOH exposure followed by withdrawal periods increases EtOH consumption similarly in both adolescent and adult mice, despite differences in BECs.
