Abstract
Abstract Recently we have shown that nerve growth factor (NGF) controls the performance of the Na+, K+ -pump in its target ganglionic neurons in suspension cultures. In the present study, enriched neuronal preparations of embryonic day 8 (E8) chick dorsal root ganglia (DRG) were obtained by means of a differential attachment procedure using tissue culture plastic dishes. Neurons were routinely seeded into polyornithine-coated 16 mm culture wells in the presence of NGF. After 18 h, cultures were switched to media with or without NGF, and containing either86Rb+ (as a tracer for K+) or22Na+ (as a tracer for Na ions). Over the next 12–15 h the cultures were assessed for numbers of surviving neurons and accumulated radioactivity. Cultured E8 chick DRG neurons fail to maintain their intracellular K+ concentration when deprived of NGF over 4–6 h. The NGF-deprived and K+- depleted neurons reaccumulate K+ within minutes of delayed NGF administration. The occurrence of this K+ response in culture to added NGF parallels the response occurring in E8 neuronal suspensions, including the time of onset of irreversibility. Similar experiments performed with22Na+ indicate corresponding ionic behaviors for cultured E8 DRG neurons. These NGF-controlled ionic responses in monolayer cultures occur for E7 and E10 neurons, but not E14 neurons and parallel the survival response to NGF of the same neurons. Blocking the pump performance by NGF deprivation leads to neuronal death. Identical results are obtained by addition of oubain or omission of external K+ in the presence of NGF. Partial reduction of pump performance by any one of these treatments leads to partial survival of the neuronal population in a precisely predictable manner. Therefore, control of the pump by NGF is an essential component of the NGF action on neuronal survival.
Published Version
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