Contribution of skeletal muscular glycine to rapid antidepressant effects of ketamine in an inflammation-induced mouse model of depression.

Basic and clinical studies have reported rapid and long-lasting antidepressant effects of ketamine. Although previous studies have proposed several mechanisms underlying the antidepressant effects of ketamine, these mechanisms have not been completely elucidated.The present study evaluated the effects of systemically administered ketamine treatment in a lipopolysaccharide (LPS)-induced mouse model of depression.Non-targeted metabolomics, western blotting, and behavioral tests (locomotion, tail suspension, and forced swimming tests) were performed.Ketamine significantly attenuated the abnormally increased immobility time in a lipopolysaccharide (LPS)-induced mouse model of depression. Aminomalonic acid, glutaraldehyde, glycine, histidine, N-methyl-L-glutamic acid, and ribose levels in skeletal muscle were altered following ketamine administration. Furthermore, ketamine significantly decreased the LPS-induced increase in glycine receptor A1 (GlyA1) levels. However, the glycine receptor antagonist strychnine did not elicit any pharmacological effects on ketamine-induced alterations in behaviors or muscular GlyA1 levels. Exogenous glycine and L-serine significantly improved depression-like symptoms in LPS-induced mice.Our findings suggest that skeletal muscular glycine contributes to the antidepressant effects of ketamine in inflammation. Effective strategies for improving skeletal muscular glycine levels may be a novel approach to depression treatment.