Suppression of pro-inflammatory cytokine expression and lack of anti-depressant-like effect of fluoxetine in lipopolysaccharide-treated old female mice

Abstract Some antidepressants show a significantly lower efficacy in elderly patients, particularly in women. Previous studies have shown that antidepressants administered to young animals reduced depression-like symptoms induced by lipopolysaccharide (LPS). The aim of this study was to find out whether the antidepressant and anti-inflammatory properties of fluoxetine (FLU) can be observed also in old female C57BL/6J mice. A depression-like state was evoked by the administration of LPS (100 μg/kg for 4 consecutive days) which was followed by reduction of sucrose preference (anhedonia) and enhancement of immobility-time in the forced swim test (FST). Animals, which received FLU (10 mg/kg, 11 days) exhibited a decreased LPS-induced expression of some inflammatory cytokines in the hippocampus and spleen but this effect was not accompanied by beneficial changes in animals' behavior. Despite the lack of antidepressant-properties of FLU in this model, our studies have proven significant profound anti-inflammatory properties of chronic FLU treatment which may suggest its suitability for fending off inflammatory processes in the elderly.