Spontaneous firing of NG108-15 cells induced by transient exposure to ammonium chloride |
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| Authors: | V. C. Kowtha H. J. Bryant V. Krauthamer K. H. Iwasa D. A. Stenger |
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| Affiliation: | (1) Naval Research Laboratory, Center for Bio/Molecular Science and Engineering, Code 6900, 20375 Washington, DC;(2) Department of Physiology, Uniformed Services University of the Health Sciences, 20814 Bethesda, MD;(3) Electrophysics Branch, DPS/OST/CDRH, U.S. Food and Drug Administration, 20857 Rockville, MD;(4) Section on Biophysics of Sensory Processes, LCB/NIDCD, National Institutes of Health, 20892 Bethesda, MD |
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| Abstract: | Summary 1. We report that NG108-15 (neuroblastoma × glioma) cells differentiated in defined serum-free media are capable of exhibiting stable automaticity (the spontaneous occurrence of regenerative action potentials) following exposure to extracellular perfusates containing NH4Cl. 2. Membrane depolarization (4–5 mV) concomitant with an increased pHi during NH4Cl exposure are followed by hyperpolarization (5–7 mV), subthreshold oscillations, and spontaneous firing after the removal of NH4Cl. 3. Cells cultured in 10% serum did not exhibit automaticity. Cells cultured in serum-free media are twice as likely to show automaticity as those cultured in reduced (1.5%) serum media. 4. We have examined factors that contribute to the events following NH4Cl exposure, namely, membrane depolarization and hyperpolarization, subthreshold oscillations, and automaticity. The inward currents activated at more negative potentials and the ionic currents associated with pronounced afterhyperpolarization in NG108-15 cells cultured in serum-free media provide a basis for the repetitive activity in general and automaticity in particular. |
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| Keywords: | NG108-15 serum-free media ammonium chloride intracellular pH |
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