Comparison of alcohol-preferring and nonpreferring selectively bred rat lines. I. Ethanol initiation and limited access operant self-administration

Several lines of alcohol-preferring and alcohol-nonpreferring rats have been developed using selective breeding based on 24-hr homecage ethanol consumption. However, it remains unclear if the selection based on two-bottle choice resulted in similar ethanol self-administration when measured using an operant procedure. In this paper, we compare our previous work using alcohol-accepting (AA) and alcohol-nonaccepting (ANA) rats with data obtained using the identical procedures in the (P) and (NP) rat lines, and both replicate lines of the high alcohol drinking (HAD1 and HAD2) and low alcohol drinking (LAD1 and LAD2) lines. All rats from each line were initiated to self-administer 10% ethanol using the sucrose fading procedure. After initiation, increasing concentrations of ethanol up to 30% ethanol were tested. The results indicated that only in the LAD1 and LAD2 lines was ethanol presentation not able to maintain lever pressing after initiation. Compared with the AA line, the P, HAD1, HAD2, and NP lines all self-administered more ethanol in the operant paradigm after initiation. The ANA line self-administered less ethanol than the AA line, but more than the LAD lines. Correlational analysis of homecage consumption with operant ethanol self-administration suggested that approximately 62% of the genetic variance in operant self-administration resulted from genes selected for the homecage drinking. At the same time, it was clear that there were genetic influences on operant self-administration that were not selected for by homecage ethanol drinking.