Chronic ethanol tolerance through free-choice drinking in the p-line of alcohol-preferring rats

Abstract

The objective of this study was to determine if the selectively bred P line of alcohol-preferring rats would develop behavioral (neuronal) tolerance with free-choice drinking of ethanol. Adult, male P rats were divided into four groups. One group (FCE) received food, water and a 10% (v/v) ethanol solution ad lib, while the control group (C) had only food and water. The other two groups received either a liquid diet containing 5% (v/v) ethanol (LDE) or a control liquid diet (LDC). All groups were kept on their respective feeding regimens for 14 days. The mean (±SEM) ethanol intakes for the FCE and LDE groups were 6.8±0.5 and 9.9±0.4 g ethanol/kg body wt./day, respectively. A shock-motivated jumping task recovery to a criterion of 75% of the performance level achieved with training. All rats were tested twice, once on the day before beginning their feeding regimens (day 0) and again 14 days later. Tolerance was assessed from differences in time of recovery to criterion performance and in blood alcohol concentrations (BACs) at recovery on day 0 vs. day 14. The mean recovery times for the C, FCE, LDC, and LDE groups on day 0 were 177±6, 170±6, 143±10 and 153±13 minutes, respectively, and the BACs were 219±6, 222±19 and 214±6 mg%, respectively. On day 14, the FCE and LDE groups exhibited tolerance with shorter recovery times of 80±7 and 70±9 minutes and higher BACs at recovery of 273±5 and 286±14 mg%, respectively. No significant differences in time of recovery or BACs were observed between days 0 and 14 for the C and LDC groups. The results demonstrated that free-choice consumption of 10% ethanol by P rats is sufficient to produce behavioral/neuronal tolerance which is similar in magnitude to that seen for P rats given ethanol in a liquid diet.