Differential vulnerability of cortical and cerebellar neurons in primary culture to oxygen glucose deprivation followed by reoxygenation

The effects of glucose and O-2 deprivation (OGD) on the survival of cortica l and cerebellar neurons were examined to characterize the biochemical mech anisms involved in OGD and OGD followed by reoxygenation. To this aim, neur ons were kept for different time periods in a hypoxic chamber with a contro lled atmosphere of 95% N-2 and 5% CO2 in a glucose-free medium. After OGD, reoxygenation was achieved by exposing the cells to normal O-2 and glucose levels, Neither MTT, an index of mitochondrial oxidative phosphorylation, n or malondialdehyde (MDA) production, a parameter measuring lipid peroxidati on, were affected by 1 hr of OGD in cortical neurons. When OGD was followed by 24 hr of reoxygenation, MTT levels were reduced by 40% and MDA was sign ificantly increased, whereas cellular ATP content did not change. Cerebella r granule cells, on the other hand, did not show any reduction of mitochond rial activity after exposure to 1 hr OGD or to 1 hr OGD plus 24 hr of reoxy genation. When OGD was prolonged for 2 hr, a significant reduction of the m itochondrial activity and of cellular ATP content occurred, coupled to a si gnificant MDA increase in cerebellar granule cells, whereas in cortical neu rons a reduction of MTT levels after 2 hr OGD was not accompanied by a decr ease of cellular ATP content nor by an increase of MDA production. Moreover , 24 hr of reoxygenation further reinforced lipid peroxidation, LDH release , propidium iodide positive neurons and the reduction of ATP content in cer ebellar granule cells. The results of the present study collectively show t hat cortical and cerebellar neurons display different levels of vulnerabili ty to reoxygenation followed by OGD. Furthermore, the impairment of mitocho ndrial activity and the consequent overproduction of free radicals in neuro ns were observed for the first time occurring not only during the reoxygena tion phase, but already beginning during the OGD phase. (C) 2001 Wiley-Liss , Inc.