Evaluation of brain damage in a rat model of neonatal hypoxic-ischemia

In spite of improvements in obstetric and neonatal care, hypoxic-ischemic brain damage with severe neurologic disability is still a clinical reality. A model in 7-day-old rats has been introduced to study the pathophysiology of perinatal hypoxic-ischemic brain damage. Unilateral brain damage is produced in the cerebral cortex, striatum and hippocampus, i.e. a similar distribution as is often seen in human asphyxiated neonates. In the present investigation the model was evaluated further by comparing three different methods to assess the brain damage: weighing the hemispheres, morphometry and somatosensory evoked potentials. Seven-day-old rats were subjected to unilateral carotid artery ligation followed by 2 h of hypoxia (7.7% O2 at 36 degrees C). After 2 h of hypoxic-ischemia pCO2 and pO2 decreased in mixed arterial/venous blood. The evaluation of the damage 2 weeks after the insult, demonstrated close correlation between morphometry and weighing (r = 0.836, P less than 0.01). The amplitude of evoked potentials correlated to the other parameters (r = 0.814, P less than 0.01 and r = 0.824, P less than 0.01 respectively) and displayed a greater relative attenuation than the other methods but with a more pronounced variability. These results indicate that the degree of brain damage can be assessed by weighing for screening purposes.