Susceptibility to, tolerance to, and physical dependence on ethanol and barbital in two inbred strains of rats.

1. Ethanol-induced sleep time was significantly longer in F344 than LEW rats. However, there is no difference in barbital-induced sleep time between F344 and LEW. 2. Development of tolerance to ethanol-induced motor impairment was slightly faster in F344 than in LEW rats. While, LEW rats more easily developed tolerance to the impairment by barbital in comparison with F344 rats. 3. F344 and LEW rats were chronically treated with liquid diet containing ethanol or with barbital-admixed food. After the termination of ethanol and barbital treatments, various withdrawal signs occurred in F344 rats, including tremor and convulsions, whereas LEW rats showed no convulsions. Withdrawal scores of ethanol and barbital were significantly higher in F344 than in LEW rats. 4. These results suggest that strain differences in physical dependence on ethanol and barbital may be mainly influenced by the susceptibility to ethanol and the development of tolerance to barbital, respectively.