Operant ethanol reward in C57BL/6 mice: Influence of gender and proceduralvariables

Food-deprived C57BL/6 (C57) mice of either sex responded for oral ethanol r ewards delivered on ratio schedules of reinforcement, thus extending to fem ale C57 mice effects previously reported only for male members of the strai n. Lever responding for ethanol reward was influenced by thirst motivation (post- vs. preprandial tests), time of access to ethanol reward, ethanol co ncentration, and reinforcement schedule. A particularly high response outpu t for 12% ethanol delivered on a PR2 schedule (e.g., similar to 1400/15 min test session) indicates its efficacy as a reinforcer for C57 mice. Estimat ed consumption of ethanol differed from lever responding when reward access time was relatively long (10 s) and response demand of the reinforcement s chedule was low, but paralleled lever responding when reward access time wa s restricted (3 s) and response demands were greater. Gender influenced lev er responding for ethanol reward and its consumption, the difference depend ing upon reward access time and reinforcement schedule. When the response d emands were low and the reward access time long, females tended to respond more than males for ethanol reward; with greater response demands and short er reward access time, males tended to respond more. In conjunction with ou r companion report, the present study helps define the behavioral condition s under which ethanol is rewarding for C57 mice and establish the condition s under which ethanol reward differs for male and female mice. (C) 1999 Els evier Science Inc. All rights reserved.