CHANGES IN EXCITATORY AMINO-ACID LEVELS AND TISSUE ENERGY METABOLITESOF NEONATE RAT-BRAIN AFTER HYPOXIA AND HYPOXIA-ISCHEMIA

Lactate accumulation, amino acid aspartate and glutamate levels, and h ypoxanthine, xanthine and malondialdehyde (MDA) concentrations were co mpared in neonate rat brain after transient global hypoxia induced alo ne or in association with unilateral ligation of a carotid artery. Lac tate production in both hemispheres was higher in cerebral hypoxia-isc hemia (CHI) than in cerebral hypoxia (CH), and was lower in CHI after 2 h than at 15 min of recovery. Aspartate and glutamate levels were re duced 15 min after CHI in both hemispheres, but aspartate alone was de creased 2 h after CHI in the ipsilateral (left) hemisphere and 15 min after CH in both hemispheres. Hypoxanthine was increased 15 min after CHI in the ipsilateral hemisphere but decreased at 2 h, whereas xanthi ne was increased. MDA production was not modified after CH or CHI. The se data, compared to those obtained in adult animals suggest that glut amate release and the capacity to generate oxygen-derived radicals are lower in neonates after ischemia. These differences might explain why the brain of the mammalian neonate is much more resistant to CH and C HI than that of the adult. (C) 1998 Elsevier Science Ireland Ltd.