Assessment of cell viability in primary neuronal cultures.

Four commonly used methods for the assessment of neuronal (or glial) cell viability are described in this unit. The MTT assay is sensitive to the function of labile mitochondrial enzymes, which typically lose activity early in the progression towards death. The lactate dehydrogenase (LDH) assay measures the appearance of this cytosolic enzyme in the bathing medium, providing a measure of plasma membrane integrity. Loss of plasma membrane integrity is also the basis of the trypan blue dye assay and the propidium iodide assay. Trypan blue staining is assessed by cell counts; propidium iodide labeling can be assessed either by cell counts, typically in conjunction with fluorescein diacetate counterstaining to identify intact cells containing adequate levels of functional esterases, or with a fluorescence plate reader.