Early hypoxia modulates the phenotype of dopaminergic cells in rat di- and mesencephalic cell cultures and induces a higher vulnerability of non-dopaminergic neurons to a second hypoxic exposure

To investigate long-term effects of hypoxia on a cellular level, di- and mesencephalic cell cultures were exposed to hypoxia on in vitro day 2 (incubation in culture medium, pO(2) = 10-20 mmHg, 24 h) and on in vitro day 13 (incubation in an electrolyte solution, pO(2) = 10-20 mmHg, 8 h). The numbers of neuron-specific enolase immune-reactive (NSE-IR) and tyrosine hydroxylase immune-reactive (IH-IR) neurons and the levels of dopamine, its main metabolites and the spontaneous and potassium-stimulated DA release were determined on DIV 15. Hypoxia on DIV 2 did not affect the numbers of NSE-IR and TH-IR neurons, but increased the dopamine content and dopamine release by about 100% in both di-and mesencephalic cultures. In addition, this hypoxia increased the vulnerability of non-TH-IR neurons to the second hypoxic episode applied during more advanced stages of the culture development on DIV 13. On the contrary, hypoxia exposure did not affect the vulnerability of TH-IR cells. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.