Effects of lipopolysaccharide infusion on arterial levels and transcerebral exchange kinetics of glutamate and glycine in healthy humans

An imbalance between glutamate and glycine signalling may contribute to sepsis‐associated encephalopathy by causing neuronal excitotoxicity. In this study, we therefore investigated the transcerebral exchange kinetics of glutamate and glycine in a human‐experimental model of systemic inflammation. Cerebral blood flow (CBF) and arterial to jugular venous concentration differences of glutamate and glycine were determined before and after a 4‐h intravenous infusion of Escherichia coli lipopolysaccharide (LPS, total dose of 0.3 ng/kg) in 12 healthy volunteers. The global cerebral net exchange was calculated by multiplying CBF with the arterial to jugular venous differences. LPS induced a systemic inflammatory response with fever, neutrocytosis, and elevated arterial levels of tumour necrosis factor‐α. This was associated with a decrease in the arterial levels of both glutamate and glycine; however, their transcerebral exchange kinetics were unaffected. Inflammation‐induced alterations of the circulating levels of glutamate and glycine, do not affect the global transcerebral exchange kinetics of these amino acids in healthy humans.