Chronic hypoxia in neuronal cell culture: metabolic consequences

Cerebral cortical cell cultures obtained from fetal mice were subjected to 5% O2 for 24 h at a developmental stage equivalent to that of the human neonate. Immediately after the hypoxic insult (HI), medium lactate was elevated and pH, partial pressure of oxygen, and bicarbonate concentration were depressed compared to controls. At this time, the cultures evidenced a modest reduction in high-affinity GABA uptake but minimal morphologic or other biochemical evidence of cellular dysfunction. Within 24 h of restitution of normoxia, there was prominent disruption of neuronal integrity as well as significant reductions in benzodiazepine (BDZ) receptor binding, clonazepam-displaceable (CLO) BDZ binding, high-affinity uptake of GABA and beta-alanine, choline acetyltransferase (ChAT) activity, and total protein. Except for the neuronal marker CLO, GABA uptake was depressed more than other parameters for the subsequent 72 h. In contrast, the non-neuronal marker, Ro5-4864-displaceable BDZ binding, was always increased. Both morphologic and biochemical changes occurred independent of correction of pH, bicarbonate, and lactate. These data suggest that chronically hypoxic nervous tissue in vitro exhibits considerable delay in the evolution of maximal abnormality but that a population of GABAergic cells may be relatively more vulnerable. Although glial cell stimulation may contribute to neuronal survival, it also is possible that, because of the temporal association with cellular dysfunction, restitution of normoxia may contribute to nervous tissue injury.