  Anhedonia is one of the key symptoms of depression in humans. Consumption of
1% sucrose solution supplemented with 0.2% vanillin was studied in two
experimental contexts in male mice living under chronic social stress induced
by daily experience of defeats in agonistic interactions and leading to
development of depression. In the first experiment, vanillin sucrose solution
was made available as an option of water during 10 days to mice living in group
home cages. Then the mice were subjected to social defeat stress and during
stress exposure they were provided with both vanillin sucrose solution and
water using a free two bottles choice paradigm. In the other experiment,
vanillin sucrose solution were first offered to mice after 8 days of exposure
to social defeat stress. Males familiar with vanillin sucrose solution showed
vanillin sucrose preference while experiencing defeat stress: consumption of
vanillin sucrose solution was about 70% of total liquid consumption. However,
the consumption of vanillin sucrose solution per gram of body weight in mice
imposed to social stress during 20 days was significantly lower than in control
males. In the second experiment, males after 8 days of social defeat stress
were found to consume significantly less vanillin sucrose solution as compared
with control males. On average during two weeks of measurements, vanillin
sucrose solution intake was less than 20% of total liquid consumption in males
with symptoms of depression and anxiety. Consumption per gram of body weight
also appeared to be significantly lower than in control group. Influence of the
experimental context on the development of anhedonia, which was measured by the
reduction in sucrose solution intake by chronically stressed male mice, has
been discussed.
