Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
6263887 | Brain Research | 2013 | 8 Pages |
â¢The unpredictable chronic mild stress model of depression is used in CD-1 mice.â¢Stress-induced anhedonic and non-anhedonic states are developed.â¢The anhedonia showed decreased hippocampal serotonin transporter protein level.â¢Fluoxetine reversed the decrease in hippocampal serotonin transporter levels.â¢The non-anhedonia showed increased hippocampal serotonin transporter protein level.
The serotonin transporter (5-HTT) regulates the extracellular concentration of serotonin, influencing neurotransmission. Evidence suggests that 5-HTT is altered during depression, but the precise changes in 5-HTT expression in the pathogenesis and treatment of depression are not clear. We investigated the protein expression of hippocampal 5-HTT in CD-1 mice exposed to unpredictable chronic mild stress for 10 continuous weeks. Following 6 weeks of the stress procedure, the mice were separated into anhedonic and non-anhedonic groups, which were then treated with fluoxetine (FLX, 10Â mg/kg/day, i.p.) for 4 weeks. Behavioral state and therapeutic efficacy of the drug treatment were assessed using sucrose preference, physical state of the coat and body weight. Our results show that changes in hippocampal 5-HTT protein expression correlated with stress-induced behavioral states. Decreases in 5-HTT expression were associated with the stress-induced anhedonic state, whereas increases were associated with the stress-induced non-anhedonic state. Following FLX treatment, the changes in 5-HTT expression were reversed in a subpopulation of anhedonic mice, i.e., the treatment-responsive anhedonic mice. The treatment did not alter the changes in the treatment-resistant anhedonic mice or in the non-anhedonic mice. The data indicate that down-regulation of hippocampal 5-HTT protein expression is a signature change associated with anhedonia, a key endophenotype of clinical depression. Differential changes in 5-HTT expression may contribute to variations in the susceptibility to anhedonia.