Voltage-dependent calcium and potassium channels in Schwann cells cultured from dorsal root ganglia of the mouse

• Published in: The Journal of physiology Vol. 441; no. 1; pp. 35 - 56
• Main Authors: Amédée, T, Ellie, E, Dupouy, B, Vincent, J D
• Format: Journal Article
• Language: English
• Published: Oxford The Physiological Society 01.09.1991; Blackwell
• Subjects: 4-Aminopyridine - pharmacology; Animals; Barium - metabolism; Biological and medical sciences; Calcium Channels - drug effects; Calcium Channels - physiology; Cells, Cultured; Cobalt - pharmacology; dorsal root ganglia; Dose-Response Relationship, Drug; Fundamental and applied biological sciences. Psychology; Ganglia, Spinal - cytology; Isolated neuron and nerve. Neuroglia; Membrane Potentials - drug effects; Mice; Nifedipine - pharmacology; potassium; Potassium Channels - drug effects; Potassium Channels - physiology; Schwann cells; Schwann Cells - physiology; Tetraethylammonium; Tetraethylammonium Compounds - pharmacology; Tetrodotoxin - pharmacology; Vertebrates: nervous system and sense organs; Peripheral nervous system; Cell culture; Calcium; Rodentia; Electrophysiology; Patch clamp method; Ionic channel; Neuroglía; Vertebrata; Mammalia; Mouse; Schwann cell; Spinal ganglion; Membrane potential; Potassium
• DOI: 10.1113/jphysiol.1991.sp018737
• ISSN: 0022-3751

1. Whole-cell patch clamp studies were carried out on Schwann cells in organotypic cultures of dorsal root ganglia (DRG) from OF1 mice embryos (18-19 days). 2. In standard external solution, from a holding potential of -70 mV, two types of voltage-dependent K+ currents were recorded: a fast transient current and a delayed sustained current. With a holding potential of -30 mV, only the delayed sustained current could be evoked. 3. Both K+ currents were inhibited by tetraethylammonium chloride (TEA) and 4-aminopyridine (4-AP) in a dose-dependent manner. For the transient current the half-maximal effective dose was 100 mM for TEA and 1.3 mM for 4-AP. For the delayed sustained current the half-maximal effective dose was 11 mM for TEA and 4 mM for 4-AP. Both currents were insensitive to external Ca2+. 4. The delayed sustained current, isolated by use of a holding potential of -30 mV displayed a 'cumulative inactivation' which was removed by hyperpolarizing the membrane to -70 mV between each test pulse. 5. In K(+)-free external and pipette solutions, with 10 mM-external Ca2+, from a holding potential of -70 mV voltage-dependent Ca2+ channel currents were recorded. The threshold for activation was -45.3 +/- 5.4 mV (mean +/- S.D., n = 5) and the current inactivated fully at the end of the test potential. The current was unaffected by 2 microM-tetrodotoxin (TTX) and totally blocked by 5 mM-Co2+. 6. Equimolar replacement of external Ca2+ by Ba2+ did not significantly modify the voltage dependence (threshold for activation -42.8 +/- 6.4 mV, n = 7) or the magnitude of the inward current. Ca2+ and Ba2+ were equally permeant. The fully inactivating current was insensitive to both nifedipine and Bay K 8644 (1 microM each). Increasing the external Ba2+ concentration from 10 to 89 mM enhanced the Ba2+ current and shifted the voltage dependence of the current (threshold for activation, -30.5 +/- 7.3 mV, n = 9) along the voltage axis as expected for altered external surface potential. 7. In 89 mM-external Ba2+ solution, some cells displayed an additional slowly decaying current which was totally blocked by nifedipine (1 microM). 8. Ca2+ channel currents were recorded only when DRG neurons were present in the culture, as excision of explants and subsequent axonal degeneration led to loss of detectable Ca2+ channel currents. This phenomenon was never observed for K+ currents. 9. We conclude that mouse Schwann cells in organotypic culture possess voltage-dependent K+ and Ca2+ channels.