Is activation of the Na+K+ pump necessary for NGF-mediated neuronal survival?

The ability of nerve growth factor to cause rapid activation of the Na+K+ pump of its responsive cells was examined by measuring the uptake of 86Rb+. A significant increase in 86Rb+ uptake in E8 chick dorsal root ganglion sensory neurons after NGF treatment was seen only if the cells had been damaged during the preparation procedure. Such damaged cells could not survive in culture in the presence of NGF, and undamaged cells that did survive in response to NGF exhibited no increased 86Rb+ uptake rate. Furthermore, cultured calf adrenal medullary cells did not show an increase in 86Rb+ uptake after treatment with NGF, although these cells respond to NGF with an increased synthesis of catecholaminergic enzymes. These results are incompatible with the hypothesis that the mechanism of action of NGF that promotes neuronal survival and enzyme induction results from an initial stimulation of the Na+K+ pump.