EFFECTS OF NERVE GROWTH FACTOR ON INTRACELLULAR FREE Ca²⁺ IN OXYGEN/GLUCOSE-DEPRIVED CULTURES FROM CEREBRAL CORTEX OF FETAL RATS

Oxygen/glucose deprived cortical cell cultures were used to explore the involvement of calcium in the mechanism of hypoxic/hypoglycemic insults and protection of nerve growth factor(NGF). Neuron viability and lactate dehydrogenase(LDH) efflux in the bathing medium of cerebral cortex cultures of fetal rats were measured as indication of the NGF effect. Calcium fluorescence indicator Fura-2/AM was used to measure free intracellular calcium(Ca²⁺i). When cultures were deprived of oxygen/glucose, massive neuronal death occurred 16～24 h following the onset of hypoxia/hypoglycemia. NGF(3～100 μg·L^-1) dosedependenly attenuated the 24 h hypoxia/hypoglycemiainduced efflux of LDH and elevated the number of surviving neurons. Hypoxia/hypoglycemia induced a reduction in Ca²⁺i in early stage and then a large elevation of Ca²⁺i in 12～24 h. NGF 50μg·L^-1 brought Ca²⁺i to normal limits during the early stage of hypoxia/hypoglycemia and prevented the later elevation in Ca²⁺i. The Ca²⁺i elevation may be involved in the cell damage in hypoxia/hypoglycemia deprived cultures. It is belived that NGF protect cerebral cortical neurons against hypoxic/hypoglycemic insults via ′stabilizing′ Ca²⁺i level or preventing the late rise in Ca²⁺i.