Formation of 4-hydroxynonenal in the supraventricular corpus callosum of postnatal rats

Lipid peroxidation is known to be associated with many neurodegenerative diseases and with trau- matic brain injury, but its occurrence in the normal de- veloping brain has not been reported. The present study was carried out using a specific antibody that recognises proteins modified by the end-product of lipid peroxide decomposition, 4-hydroxynonenal (HNE), to evaluate evaluate possible lipid peroxidation products in the brains of developing rats by immunocytochemistry and electron microscopy. Moderately dense labelling was observed in the supraventricular corpus callosum in the 7- and 8-day-old rats, whilst very dense labelling was observed in the same region, in the 9- and 10-day-old rats. Very little immunoreactivity was observed at 14 days, and no staining was observed in the corpus cal- losum in adult rats. HNE staining was not observed in neuronal cell bodies that give rise to callosal axons in the overlying cerebral cortex. Electron microscopy showed dense HNE staining on the basal laminae of blood vessels and on the plasma membranes of unmyeli- nated axons. Large numbers of rounded cells with fea- tures of oligodendrocyte precursor cells were labelled by Perl's stain in the supraventricular corpus callosum at postnatal day 7 and postnatal day 10, i.e. at times cor- responding to high levels of HNE immunoreactivity. In contrast, very few such cells were observed in the adult brain, corresponding to the very little or no Perl's stain- ing in the adult. These results suggest that lipid peroxi- dation observed in the supraventricular corpus callosum at postnatal day 10 could result from an accumulation of iron in this region, at this time.