Differences in ethanol sensitivity and acute tolerance between UChA and UChB rats

In order to learn more about the genetic factors that determine the different responses to ethanol that contribute to the voluntary consumption of ethanol, this study examines the sensitivity to a nonnarcotic dose of ethanol (2.3 g/kg IP) of rats genetically selected for their low (UChA) and high (UChB) ethanol voluntary consumption.

Sensitivity was evaluated by studying both ethanol-induced (2.3 g/kg) motor impairment in a modified tilting-plane test and hypothermia. Blood ethanol concentration obtained after the ethanol dose and the correlation between ethanol sensitivity and voluntary ethanol consumption were also studied.

Results obtained with both tests revealed that UChB rats were less sensitive to ethanol than UChA ones. The genetic difference in motor impairment appeared not to be the result of different blood ethanol levels. Furthermore, rats of both strains recovered motor activity when blood ethanol was at the highest level, indicating the development of acute tolerance. The acute tolerance appeared to develop in shorter time in UChB than in UChA rats. In contradistinction, time course of hypothermia was significantly related to that of blood ethanol. A significant correlation between motor impairment and ethanol voluntary consumption (p<.001) was obtained.

The difference in motor impairment reported here might be related to differences between the strains in the ability to develop acute tolerance to ethanol. Acute tolerance development appears to be positively correlated to voluntary ethanol consumption by the rat.