In an attempt to probe the relationship between excitotoxicity and increases in intracellular calcium ([Ca2+]i), BAPTA-AM and its analogs were applied to cultured hippocampal neurons. Chelation of [Ca2+]i depressed and prolonged transient responses to glutamate and did not effect elevation of [Ca2+]i by prolonged exposure. This explains the inability of the chelators to prevent glutamate-induced toxicity.