MAP2 provides reliable early assessment of neural injury in the newborn piglet model of birth asphyxia

Reduction in microtubule-associated-protein-2 (MAP2) immunoreactivity is a sensitive and quantifiable early marker of neural injury in rats. This study assessed the reliability of MAP2 as an early marker of neural injury following hypoxia/ischaemia in neonatal piglets, and compared the effects of perfusion and immersion fixation on MAP2 immunoreactivity. Hypoxia was induced in newborn piglets (n = 23) by reducing the FiO2 to 4% for 0, 25, 35 or 50 min. Six hours after the end of hypoxia piglets were killed, and the brain removed and immunolabelled for MAP2. Significant reductions in MAP2 immunoreactivity were seen in cortex, hippocampus, basal ganglia and thalamus. Reductions correlated with duration of hypoxia, pH at the end of hypoxia, cerebral function monitor amplitude and cerebral impedance 6 h after hypoxia, and with early histological evidence of ischaemic changes. Regions with reduced immunoreactivity correlated with areas where damage is present in later histological examination in this model. Immersion fixation with postmortem delays up to 30 min did not affect MAP2 immunoreactivity compared to perfusion-fixed tissue. Results indicate that MAP2 immunoreactivity 6 h after hypoxia/ischaemia is a reliable marker of neural injury in the neonatal piglet.