BRAIN INJURY AFTER HYPOXIA-ISCHEMIA IN NEWBORN RATS - RELATIONSHIP TOEXTRACELLULAR LEVELS OF EXCITATORY AMINO-ACIDS AND CYSTEINE

The aim of this study was to follow extracellular concentrations of ex citatory amino acids (EAAs) and cysteine during neonatal hypoxia-ische mia (HI) and reflow and to relate these events to the extent of brain damage evaluated 6 h after the insult. Rat pups (PND 7-10) were subjec ted to unilateral ligation of the common carotid artery and exposed to hypoxia (7.7% O-2). Extracellular amino acids were sampled during HI and for 6 h of reperfusion with microdialysis and the levels were corr elated with the extent of brain damage at the site of probe placement. The concentrations of glutamate, aspartate and cysteine increased tra nsiently during HI (15 X, 6 X and 3 X, respectively) in the extracellu lar space and returned to normal or remained slightly elevated during reperfusion. Changes of EAAs and cysteine were similar during HI in th e infarcted, undamaged and border-zone regions. During reperfusion the concentrations of glutamate, aspartate and cysteine were higher in in farcted and border-zone areas compared to undamaged tissue. In neonata l rats, the extracellular levels of EAAs during HI do not correspond t o the extent of brain injury whereas the EAA concentrations during ref low are related to the extent of infarction.