Calcium indicators and excitotoxicity in cultured cortical neurons

Membrane-permeating, fluorescent Ca2+ indicators have been used to investigate the role of increased intracellular Ca2+ (Ca2+i) levels in excitotoxic neuronal injury, but their ability to chelate Ca2+i and their own toxic effects in some cells could obscure this relationship. N-Methyl-D-aspartate (NMDA)-stimulated Ca2+i responses and toxicity were measured in neuron-enriched rat cerebrocortical cultures loaded with either fluo-3 or fura-2. Ca2+i responses signaled by both indicators were similar in magnitude, and neither indicator reduced NMDA toxicity, measured by lactate dehydrogenase (LDH) release. Fluo-3 and fura-2 appear to be suitable for comparative studies of NMDA-induced Ca2+i responses and excitotoxicity.