Animal model of ethanol abuse: rats selectively bred for high and low voluntary alcohol intake

The selectively bred alcohol-preferring and alcohol-non-preferring lines of rats have been used to study the biology of alcohol abuse and dependence. In our laboratory new lines of Wistar rats have been selectively outbread for 7 years and 19 generations for high and low ethanol intake (WHP--Warsaw High Preferring) and WLP--Warsaw Low Preferring respectively). After the first selection procedure, the highest scoring females and males were used initiate upward selection, while the lowest scoring pairs were used to initiate downward selection. Mated pairs were housed in breeding cages, pups were allowed to nurse for 3 weeks before weaning, then the pups of each litter were culled to the same-sex cage and allowed to mature until they were subjected to the selection procedure. In order to determine the alcohol intake and preference, the rats were individually housed in wire cages containing two graduated drinking tubes mounted at the front. During the entire investigation, the subjects had free access to standard lab chow (Bacutil, Poland). Ethanol solution was prepared from 95% stock ethanol and tap water. The animals were presented with 10% ethanol solution and water (two-bottle choice test). The drinking tubes were rotated daily to prevent position preference. Alcohol intake was calculated as average g/kg/day (absolute ethanol) while alcohol preference (in %) was calculated as the amount of alcohol consumed/total fluid x 100. Our results (17-19 generations) have shown that mean alcohol intake in WHP rats was higher than 5.0 g/kg/24 h ethanol, while WLP rats generally consumed less than 2.0 g/kg/24 h ethanol. Our results also showed that the total fluid intake in WHP rats slightly but not significantly higher as compared with WLP rats. Maximal ethanol consumption (in both lines) occurred during the natural dark phase three bungs (19.00-20.00 hrs, 23.00-02.00 hrs and 04.00-05.00 hrs). Interestingly, the intakes of high concentrations of sucrose and saccharin solutions were significantly higher in WHP than in WLP rats. Furthermore, the WHP rats reduced their alcohol and water intakes in the presence of 10% sucrose solution. Thus, it appears that high consumption of sweets may be a neurobiological factor promoting increased ethanol intake by WHP rats.