AMINO-ACIDS IN CEREBROSPINAL AND BRAIN INTERSTITIAL FLUID IN EXPERIMENTAL PNEUMOCOCCAL MENINGITIS

Excitatory amino acids are increasingly implicated in the pathogenesis of neuronal injury induced by a variety of CNS insults, such as ische mia, trauma, hypoglycemia, and epilepsy. Little is known about the rol e of amino acids in causing CNS injury in bacterial meningitis. Severa l amino acids were measured in cerebrospinal fluid and in microdialysi s samples from the interstitial fluid of the frontal cortex in a rabbi t model of pneumoccocal meningitis. Cerbrospinal fluid concentrations of glutamate, aspartate, glycine, taurine, and alanine increased signi ficantly in infected animals. Among the amino acids with known excitat ory or inhibitory function, interstitial fluid concentrations of gluta mate were significantly elevated (by 470%). Alanine, a marker for anae robic glycolysis, also increased in the cortex of infected rabbits. Th e elevated glutamate concentrations in the brain extracellular space s uggest that excitotoxic neuronal injury may play a role in bacterial m eningitis.