A simple, objective method to measure the activity of factors that promote neuronal survival

The activity of factors that promote short-term neuron survival (neurotrophic or neuronotrophic factors) can be quickly and objectively determined by measuring the incorporation of radiolabelled leucine or methionine during the 24 h duration of the assay. Other types of radiolabelled small molecules, such as choline or 2-deoxyglucose, can also be used but their signal/noise ratios are not as favorable under the optimal assay culture conditions. The neuronotrophic titers determined by amino acid uptake are the same as those estimated by microscopic counting of live and dead neurons.