Different chronic ethanol exposure regimens in adolescent and adult male rats: Effects on tolerance to ethanol-induced motor impairment

Findings are mixed regarding the expression of tolerance after repeated ethanol exposure, perhaps in part due to dose/frequency variations in exposure regimens. The present study compared age-related differences in tolerance development following 10 days of 1 g/kg twice daily, 2 g/kg once daily, or intermittent 4 g/kg ethanol exposure regimens. To measure expression of chronic tolerance and acute tolerance, ethanol-induced motor impairment was assessed on day 12, with functionally equivalent ethanol doses administered across age (2 g/kg - adolescents: 1.5 g/kg - adults). Subsequent challenge doses resulted in lower brain ethanol concentrations in both age groups as a function of the chronic ethanol regimens. Expected age-related differences emerged in acute tolerance expression in non-manipulated animals, with adolescents, but not adults showing acute tolerance. Regimens sufficient to induce alterations in ethanol metabolism did not result in chronic functional tolerance at either age, although chronic injections were sufficient to induce acute tolerance in adults. (C) 2011 Elsevier B.V. All rights reserved.