Neuroinflammation has been attracted attention as an underlying mechanism of major depression. New animal models based on this hypothesis have been developed. These new models could be useful to evaluate new types of therapeutic agents. Based on this hypothesis, we tried to establish a Lipopolysaccharide (LPS)-induced depression model in mice to assess the effects of antidepressants.
LPS was injected i.p. at a dose of 0.8 mg/kg to male BALB/c mice the day before behavior testing. As the behavioral tests, the tail suspension test (TST) and the forced swimming test (FST) were used.
The immobility time in the TST and FST was prolonged in the LPS treated mice compared with the normal control. Effects of various antidepressants, such as tricyclic, SSRI, and ketamine were evaluated. These drugs reduced the immobility time of the model mice in both behavioral tests.
It is considered that the depression model in mice was established using LPS. As advantageous points, this model is free from stressful manipulation to animals and is sensitive to both traditional and new antidepressant drugs. The model would be useful to evaluate potential efficacy of newly developed antidepressants.