Mice exposed to a 30 min restraint episode immediately prior to the fluid consumption test drank approximately 2.40 g (90 g/kg body weight) of 10% sucrose solution and approximately 0.25 g (10 g/kg body weight) of water. reduced sucrose preference that was unaffected by CP55940 and URB597. However, rimonabant produced a greater reduction in sucrose preference on day 10 compared to day 1. These data suggest that on day 10, endocannabinoid signaling is usually maximally activated and essential for incentive sensitivity. The findings of the present study indicate that this CB1/endocannabinoid signaling system is an important Rabbit Polyclonal to ADCK5 allostatic mediator that both modulates the responses of mice to stress and is itself modulated by stress. and were approved by the Medical College of Wisconsin Institutional Animal Care and Use Committee. All efforts were made to minimize the number of mice used and their suffering. 2.2. Materials Graduated glass bottles, stoppers, and drinking tubes were purchased from Ancare Corp. (Bellmore, NY). Sucrose and saccharin were purchased from Sigma Chemical Co. (St. Louis, MO). Rimonabant (SR141716) and CP55940 were provided by the NIDA Drug Supply Program (Research Triangle Park, NC). URB597 was purchased from Cayman Chemical (Ann Arbor, MI). CP55940 and rimonabant were dissolved in an emulphor vehicle consisting of a ratio of 1 1:1:18 for drug in DMSO-emulphor-saline. URB597 was dissolved in an emulphor vehicle consisting of a ratio of 1 1:1:8 for drug in DMSO-emulphor-saline. Drug was delivered by i.p. injection in a volume of 1 ml/kg. Control animals received an comparative i.p. injection of the vehicle without drug. Mice received only a single injection of drug or vehicle that was administered one hr prior to the fluid consumption test. 2.3. Fluid consumption Mice were habituated to consume either a sucrose (10% w/v) or saccharin (0.1% w/v) answer by providing sucrose or saccharin as the only drinking fluid for 48 hrs. After habituation, baseline sucrose or saccharin preference was measured for five consecutive days. During the daily fluid preference test, which lasted for 60 min, mice experienced concurrent access to either sucrose (10 %10 % w/v) or saccharin (0.1% w/v) answer and tap water. A 10% w/v sucrose answer was selected since sucrose consumption has been shown to be concentration-dependent, with the highest IRAK-1-4 Inhibitor I amount of sucrose consumed at a concentration of 10% w/v (Katz, 1982). Therefore, this assay is usually biased towards detection of decreases in sucrose consumption and is less sensitive to increases in consumption. Fluid intake was measured by weighing the bottles before and after the preference test. Sucrose, saccharin, and water consumption was determined by dividing the mass of answer consumed in g by body weight in kg. Sucrose and saccharin preference, measured to account for possible between-group differences in water consumption, was determined by dividing IRAK-1-4 Inhibitor I sucrose or saccharin consumption by total fluid consumption. Consistent with previous studies of the effect of stress on the consumption of highly palatable solutions, all mice were deprived of food and water for 20 hrs preceding each fluid preference test (Papp et al., 1993; Sampson et al, 1991; Willner et al., 1987). Immediately after completion of the fluid preference test, mice experienced access to food and water for 4 hrs in their home cages. 2.4. Stress process Mice were acclimated to the screening room for 24 hrs IRAK-1-4 Inhibitor I prior to experimentation. All mice were marked on their tail once daily for identification. All mice were food and water deprived and subjected to the fluid consumption process. Mice were stressed by restraint for 30 min in altered, transparent 50 ml plastic conical tubes with numerous air flow holes to increase ventilation (Patel et al., 2004). Non-restrained mice were left undisturbed in their home cage during the restraint process. In each study, sucrose preference was decided in four groups of mice: mice injected with IRAK-1-4 Inhibitor I vehicle 60 min prior to the fluid consumption test without restraint stress (An level of 0.05 was utilized for all statistical assessments. 3. Results 3.1. Restraint stress effects on sucrose preference Mice habituated to the fluid consumption process drank approximately 3.75 g (140 g/kg body weight) of 10% sucrose solution and approximately 0.25 g (10 g/kg body weight) of water during a 60 min fluid consumption period. Mice exposed to a 30 min restraint episode immediately prior to the fluid consumption test drank approximately 2.40.