2.2. Chronic mild stress model and sucrose consumption test

A chronic mild stress procedure was carried out according to the method of Muscat et al. [33]. Briefly, rats trained for palatable weak (1%) sucrose solution consumption and grouped such that they would not differ in the amount of sucrose solution consumed were exposed to different stressors in a randomized order. In the 3-week chronic mild stress model, the animals were exposed to the following stressors: 17 h isolation in the cage, exposure to stroboscopic light for 7, 9 and 17 h, nightlong light exposure, keeping in a 45º sloped cage for 7 and 17 h, deprivation of water and food for 20 h, exposure to 85 dB noise for 3 and 5 h, keeping in the cage with an empty bottle for 1 h, and limiting water and food access at various times. At the end of each week, rats were deprived of food and water for 12 h, and were subjected to 1 h sucrose consumption test. The amount of sucrose solution consumption was measured for each rat and averaged across groups by weighing the bottles prior to and after the test. At the baseline (week 0) the consumption of the groups was accepted as 100%, and weekly percentage change in the consumed amount of sucrose solution of groups was calculated. All experiments were performed between 08:00 a.m. and 12:00 p.m.