Voltage-dependent calcium and potassium channels in Schwann cells cultured from dorsal root ganglia of the mouse
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 transien...
Saved in:
Published in | The Journal of physiology Vol. 441; no. 1; pp. 35 - 56 |
---|---|
Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
Oxford
The Physiological Society
01.09.1991
Blackwell |
Subjects | |
Online Access | Get full text |
Cover
Loading…
Summary: | 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. |
---|---|
Bibliography: | ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 ObjectType-Article-1 ObjectType-Feature-2 |
ISSN: | 0022-3751 1469-7793 |
DOI: | 10.1113/jphysiol.1991.sp018737 |