The effects of ethanol initiation procedures on ethanol reinforced behavior in the alcohol-preferring rat

Rats from the alcohol preferring (P) line developed at Indiana University were initiated to self-administer ethanol orally without food or water restriction using either a sucrose-fading or a secondary-conditioning procedure. Following initiation, they were tested under a variety of operant conditions to examine the ability of ethanol to reinforce lever pressing behavior. Regardless of initiation procedure, the animals maintained lever pressing behavior with ethanol reinforcement, even at ethanol concentrations as high as 40% (v/v). Slightly higher daily session intakes (g/kg) were found at the higher ethanol concentrations following the secondary-conditioning initiation procedure compared with the sucrose-fading technique. When both ethanol and water were concurrently available, the rats showed a high preference for ethanol reinforcement. When varying concentrations of sucrose were substituted for water, the amount of ethanol ingested decreased as the concentration of the alternative sucrose increased. However, if the response requirement for the sucrose was substantially greater than that for ethanol, the rats shifted their responding to the lever associated with ethanol presentation. The results are discussed in relation to prior work using similar procedures with Long-Evans non-selected rats and with the alcohol non-preferring (NP) rat line.