Antidepressant-like effects of a novel pentapeptide,nemifitide, in an animal model of depression

Background Nemifitide is a novel peptide analog of melanocyte-inhibiting factor (MIF) that has been reported to relieve depressive symptoms in a very short period.Objectives The Flinders Sensitive Line (FSL) rat, a genetic animal model of depression with innate exaggerated immobility in the forced swim test, was used to obtain more detailed information about the antidepressant-like effects of nemifitide.Methods The FSL rats were treated chronically with various doses of nemifitide or reference antidepressants desipramine and fluoxetine for 5 or 14 days and the forced swim test was conducted 22–24 h after the last treatment.Results Nemifitide significantly increased swimming in the FSL rats at both low (0.025–0.3 mg/kg) and high (3.0–15.0 mg/kg) doses but not at intermediate (0.4–2.4 mg/kg) doses. Nemifitide (0.3 mg/kg) and desipramine (5.0 mg/kg) significantly increased swimming in the FSL rats after just 5 days of treatment, but fluoxetine (5.0 mg/kg) did not. Nemifitide (0.3 mg/kg) and fluoxetine (5.0 mg/kg) had long-lasting effects, but desipramine (5.0 mg/kg) did not.Conclusions These findings support the value of developing nemifitide and its analogs as potential antidepressants.