Increased sodium ion conductance through nicotinic acetylcholine receptor channels in PC12 cells exposed to nerve growth factors.

22Na+ uptake in response to cholinergic stimulation was measured in PC12 cells grown in media containing either beta-nerve growth factor (NGF) from mouse submaxillary gland or a component of Bungarus multicinctus venom (fraction 9B) which has nerve growth factor activity. Our results showed that each of these nerve growth factors increased the Na+ conductance capacity of ACh receptor-linked ion channels in PC12 cells. Compared to untreated cells, Na+ uptake was enhanced by about 40% in cells exposed for 24 to 30 hr to either 50 ng/ml of beta-NGF or to 5 micrograms/ml of fraction 9B. This cholinergically stimulated Na+ flux increased with time and reached a level 2- to 3-fold higher than that of untreated cells after 4 to 6 days' exposure to NGFs. The generation of neurites in response to NGFs from either source occurred with the same time course as the increase in Na+ channel conductance. Growth factor-enhanced Na+ uptake remained for several days after NGFs were removed from cells and neurites were lost. Na+ flux into untreated and into 9B- or beta-NGF-treated cells was inhibited to a greater extent by a nicotinic than by a muscarinic antagonist. Dibutyryl cyclic AMP did not cause an increase in Na+ uptake in response to cholinergic agonists at concentrations which stimulated neurite-like process formation, and dibutyryl cyclic AMP did not potentiate the effects of NGFs.