Determination of intracellular Ca2+ concentration can be a useful tool to predict neuronal damage and neuroprotective properties of drugs

The purpose of the present study was to examine the relationship between elevation in intracellular Ca2+ concentration ([Ca2+](i)) and development of neuronal damage after cytotoxic hypoxia in vitro. Chick telencephalic neurons were exposed to NaCN 1 mM for up to 2 h. [Ca2 +](i) was assessed by means of fura-2 based microfluorometry and viability was measured by means of trypan blue exclusion on the same relocated cells for a period of 24 h after initiation of hypoxia. Exposure to sodium cyanide resulted in an up to 10 fold increase in [Ca2+](i) and led to subsequent neuronal damage. According to [Ca2+](i) and viability neurons in four different stages could be revealed. The percentage of neurons showing elevated [Ca2+](i) paralleled exactly the percentage of neuronal damage. The elevation in [Ca2+](i) clearly preceded neuronal damage suggesting a time window for pharmacological intervention. The NMDA antagonists dizocilpine, memantine and amantadine were capable of reducing the percentage of neurons showing elevated [Ca2+](i) and attenuated neuronal damage. Dizocilpine proved to be the most potent and amantadine to be the weakest antagonist whereas the alpha-amino-3-hydroxy-5-methyl-isoxazole-4-propionate (AMPA) antagonist 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo-(F)-quinoxaline (NBQX) was ineffective. Under our experimental conditions, measurement of [Ca2+](i) was able to predict the extent of neuronal damage as well as the neuroprotective potency of drugs.