Brain excitatory amino acid concentrations are lower in the neonatal pig: A buffer against excitotoxicity?

Hypoglycemic brain damage has been associated with high levels of the excit atory amino acids (EAA) aspartate and glutamate in the newborn and adult. W e hypothesized that newborn piglet EAA would be different from those of old er pigs when stressed with severe insulin-induced hypoglycemia (< 30 mg/dl) . Brain EAA were measured in piglets and adolescent pigs via microdialysis. Eleven of 12 newborn normoglycemic piglets had no detectable baseline leve ls (<0.5 muM) of EAA, while pigs had aspartate and glutamate concentrations of 1.78 +/- 0.44 and 3.43 +/- 1.14 muM (mean SEM), respectively. Piglet as partate and glutamate concentrations reached but did not significantly exce ed normoglycemic pig levels after 2 h with plasma glucose values less than or equal to 20 mg/ml. Elevations in EAA were only detected in piglets whose EEG activity ceased. Aspartate and glutamate concentrations did not increa se in insulin-treated pigs nor in control animals. We speculate that newbor ns with blood glucose less than clinically acceptable values (35 mg/dl) may be protected from EAA-associated neuronal damage during acute hypoglycemia . Lower normoglycemic and hypoglycemic levels of EAA in newborns when compa red to older pigs provide this protection. Copyright (C) 2001 S. Karger AG, Basel.