Unpaired t tests were used to compare the significance between the latencies in different genotypes. Locomotor activity was measured by scoring beam breaks in activity chambers (San Diego Instruments). Prior to open-field tests, animals were handled for 2 consecutive days. Standard rat cages were used as the novel open field for the mice tested. Locomotor activities were recorded Selleckchem I BET151 for 1 hr and scored for both 5 min and 1 hr. Unpaired t tests were used to compare the significance in fine movements, ambulatory movements, and rearing between the different
genotypes. Mice were placed on a food-deprivation schedule to reduce their weight to 80%–85% of their baseline weight. They were fed for 2 hr with mouse chow in their home cages each day after training. Water was available at all times in the home cages. Training and testing took place in eight Med Associates operant chambers (21.6 cm length × 17.8 cm width × 12.7 cm height) housed in boxes with sound-attenuating walls. Each chamber was equipped with a food magazine, two retractable levers, one on each side of the magazine, and a 3 W, 24V house light mounted on the same wall, but above the food magazine. Bio-Serv 20 mg pellets from a dispenser into the magazine were used as reward. The software Med-PC-IV from Med Associates was used for equipment control and behavior recording. At the beginning of
each session, the house light was turned on and the lever inserted. At the end of Ion Channel Ligand Library purchase each session, the light was turned off and the lever retracted. Mice were trained in an initial lever-press training consisting of 4 consecutive days of CRF, during which the mice received a pellet for each lever press. A session would end after 60 min
or after the mouse had collected 30 rewards, whichever came first. After CRF, mice were trained with RI schedules to generate habitual lever pressing (Dickinson et al., 1983). The training started with 2 days on RI 30 s, with a 0.1 probability of reward availability every 3 s contingent on lever press, and followed by 6 days on the 60 s interval schedule, tuclazepam with a 0.1 probability of reward availability every 6 s contingent on lever pressing. Repeated-measures ANOVA was used to compare lever press between the different genotypes. A specific satiety procedure was used for outcome devaluation. Mice were given unlimited access within a fixed duration to either the mouse chow to which they had been exposed in their home cages (nondevalued condition/control), or the purified pellets they normally earned during lever-press sessions (devalued condition). The mouse chow served as a control for overall level of satiety. This procedure controls the overall level of satiety and motivational state, while altering the current value of a specific reward. Immediately after 1 hr of unlimited exposure to the pellets or chow, the mice were subjected to a 5 min long probe test.