Some mammalian neurons undergo apoptosis after neurotrophin deprivation. We studied neuronally differentiated PC6-3 pheochromocytoma cells, which are highly dependent on nerve growth factor for survival. We found that transient transfection with green fluorescent protein or beta-galactosidase protected cells from apoptosis induced by nerve growth factor deprivation. Individual transfection reagent components did not produce increased viability of nerve growth factor-deprived cells. This apparent neuroprotective effect from transient transfection was specific to neurotrophin deprivation, as cells treated with H(2)O(2) or staurosporine were not protected. To determine the mechanism of neuroprotection after transfection, the transfection status of identified groups of cells was assessed both before and after nerve growth factor deprivation. The results were consistent with a model whereby cells that are transfected but not yet expressing the transfected protein are relatively protected from nerve growth factor deprivation. We suggest that apoptosis induced by neurotrophin deprivation may interact with processes of transient transfection and expression of foreign genes in neuronal cells. Not only should these interactions be considered in transient transfection studies of neurotrophin-deprived neurons, but also their elucidation could lead to novel methods for achieving neuroprotection.