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Background The still maturing adolescent brain may be particularly vulnerable to lasting consequences of ethanol exposure. Yet, human adolescents are the age group most likely to engage in binge drinking (a pattern of drinking leading to blood ethanol concentrations (BECs) of 80 mg/dl or greater). Most studies to date assessing the long-term effects of adolescent ethanol exposure in outbred rodent populations have either used experimenter-administered ethanol to produce BECs in the binge range or assessed voluntary intake of ethanol at well below binge levels. Beginning with a modified schedule-induced polydipsia (SIP) procedure, this study examined the suitability of several approaches to induce voluntary binge-like consumption during adolescence in an outbred rat strain. Methods Adolescent male and female Sprague-Dawley rats were food deprived to 85% projected free-feeding weights beginning on postnatal day (P) 24, and were given 30 minutes of access to 10% ethanol in chocolate Boost® or Boost® alone daily from P28 to P41 (followed later by their daily allocation of food). Animals were tested within operant chambers (Exp.1a,1b,2) or home and novel cages (Exp.3). Animals received either scheduled delivery of banana pellets to examine schedule-induced polydipsia (Exp.1a,b) or massed pellet presentation (Exp. 2,3). Blood samples were collected via the lateral tail vein on P33 and P41. Results Intakes produced BECs frequently in the binge range (> 80mg/dl) and modeled binge-like consumption patterns, with high consumption days typically followed by 1–2 days of lower consumption; this variability was less evident with Boost® alone. Consumption was not schedule-induced, and was generally high across all studies, although consumption in males appeared to be particularly pronounced when animals were tested in the presence of their cage mate. Conclusions Binge-like patterns of ethanol consumption were produced using these procedures in adolescent Sprague-Dawley rats of both sexes, and may prove to be a useful model for work examining the short- and long-term consequences of high levels of voluntary ethanol intake in adolescence.

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BackgroundIn rodent studies of ethanol (EtOH) consumption where blood sample collection does not occur, there is often mention of likely BECs based on prior studies. These studies may vary in dose(s) used, age/sex/species, or administration route. Often, intake studies may presume that binge-levels were achieved without knowing that BECs exceeded 80 mg% (binge threshold). In human studies, estimated BECs (eBECs) have been derived using complex formulas that consider EtOH consumption level and the weight and sex of the individual.MethodThree datasets were used to derive eBECs using a conversion factor (CF) that considers gram (g) of EtOH per kilogram (kg) of animal weight and other variables that may influence BECs such as age, sex, dose, route, vehicle, chronicity, and timing post-exposure. Regression analyses were also conducted for each dataset, building regression models with BEC as the response and other variables in the study specific to each dataset as predictor variables.ResultsDataset1 assessed age, sex and post-injection time point. Both CF and regression analyses determined that different CFs should be used for 10- and 30-min post-administration time points. Dataset2 assessed age, dose, vehicle and post-intubation time point. Depending on the post-intubation time point, several CFs were used to derive eBECs. When weight was not used as a regression variable, data across approaches corresponded, with age differences emerging later in elimination phase. In Dataset3 that used BECs from a repeated intake study, chronic exposure influenced CFs, although regression analysis did not yield similar findings.ConclusionsAlthough eBECs can be derived, critical variables vary with subject and test conditions and do not always concur with results of regression analyses. Although, not designed to replace assessment of BECs when sample collection is possible, the CF approach may prove useful when estimating BECs in studies where assessments are not feasible.