Anhedonia

Mice were housed in separate home cages and were presented with two separate bottles of water every 24 h for 3 consecutive days to record baseline consumption (W-W comparison). Following training, one of the water bottles was replaced with one containing a sucrose (0.5, 1, or 2%) or quinine (15 or 30 mM) solution. Each concentration of sucrose or quinine was presented for 3 consecutive days with the positions of the water and sucrose or quinine bottles switched daily. Several days with a single water bottle were interposed between sucrose or quinine concentration tests. For each test, sucrose or quinine, the lowest concentration was presented first and progressed to the highest concentration. Quinine testing was conducted after sucrose testing was completed. Preference scores were calculated as: [(volume of sucrose or quinine consumed – volume of water consumed)/total volume of liquid consumed]. For each concentration of sucrose or quinine, the average preference score over the 3 test days was calculated for each animal, including the average total volume of fluid consumed.