Differential response of immature and mature neurons to hypoxia in rat mesencephalic cultures

The effect of hypoxia on immature and mature mesencephalic neurons was studied in in vitro rat cerebral cell cultures on different days. In immature cultures (6-8 days in vitro), exposure to 24 h of hypoxia (10-20 mm Hg pO(2) in the culture medium) did not change the number of neuron-specific enolase (NSE)-immunoreactive (IR) (NSE-IR) neurons but increased the number of tyrosine hydroxylase (TH)-IR (TH-IR) cells, which might be attributed to transient induction of TH. In mature cultures (1315 days in vitro), 16 h of hypoxia induced a considerable loss of both NSE- and TH-IR cells. A decrease in the number of TH-IR cells 6 and 24 h after hypoxia was more pronounced than that of NSE-IR cells; however, their numbers equalized 48 h after hypoxia, suggesting similar hypoxic vulnerability of dopaminergic and nondopaminergic neurons in mature mesencephalic cultures. In immature cultures, hypoxia slightly stimulated both apoptosis and necrosis, while in mature cultures, it dramatically increased the number of solely necrotic cells. Copyright (C) 2002 S. Karger AG, Basel.