Variables affecting acquisition and maintenance of operant ethanol self-administration in male and female Long-Evans...

The goal of the present study was to determine the effect of prior experience with ethanol drinking and changes in session duration on the acquisition and maintenance of operant ethanol self-administration.

Adult male and female Long-Evans rats were trained to operantly self-administer ethanol. A subset of rats underwent 3 weeks of intermittent-access two-bottle choice drinking in the home cage prior to operant training. Controls were given access to two bottles of water. Once fully trained in 30-min operant sessions, the session duration was reduced to 15 min for all rats. Differences between 30- and 15-min sessions were also assessed in a separate group of rats trained to self-administer sucrose.

No differences were observed in acquisition rates, the magnitude of responding for ethanol, or total ethanol consumed between rats allowed to drink ethanol in the home cage and those that remained ethanol naïve prior to operant training. A significant decrease in appetitive and consummatory behaviors was observed in rats trained to lever press for either ethanol or sucrose when session length was reduced from 30 to 15 min. Assessment of within-session drinking patterns suggests that this is driven primarily by missed drinking opportunities occurring during the second half of 30-min sessions.

These data suggest that prior short-term home cage ethanol drinking offers little advantage as an initiation procedure over no initiation procedure at all. Moreover, reducing operant session duration from 30-min to 15-min has the potential to decrease, rather than increase, levels of ethanol intake.