Oral operant ethanol self-administration in 5-HT1b knockout mice.

The present experiment examined oral ethanol self-administration in 5-HT1b knockout (KO) mice and 5-HT1b wide-type (WT) control mice using a continuous access operant procedure. After lever press training, adult 5-HT1b KO and 5-HT1b WT mice were placed in operant chambers on a 23 h per day basis with access to food (FR1), 10% v/v ethanol (FR4), and water from a sipper tube. KO mice displayed higher rates of responding on the ethanol-associated lever compared to WT mice. KO mice also consumed greater amounts of water. Food responding was the same in both genotypes. Following 30 sessions, ethanol concentration was altered every 5 days. Response patterns were determined using 0, 5, and 20% v/v ethanol concentrations. Ethanol responding (0, 5, 10, and 20% v/v) was also examined after the addition of 0.15% saccharin. KO mice and WT mice showed similar response rates for all ethanol concentrations. Since KO mice showed greater levels of ethanol responding only for unsweetened 10% v/v ethanol, and showed modest ethanol self-administration overall, the present results are not consistent with the notion that 5-HT1b KO have a generally greater preference for ethanol than 5-HT1b WT mice.