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Ionic currents in isolated and in situ squid Schwann cells
Isao Inoue1, Izuo Tsutsui, N Joan Abbott
1Institute for Enzyme Research, Tokushima University, Japan.
The Journal of Physiology
|June 18, 2002
Summary
Ionic currents in squid Schwann cells were analyzed using patch clamp techniques. Researchers identified voltage-gated calcium and calcium-activated potassium channels crucial for membrane potential regulation.
Area of Science:
- Neuroscience
- Cell Biology
- Biophysics
Background:
- Schwann cells in squid giant axons play a vital role in nerve impulse conduction.
- Understanding ionic currents in these cells is key to comprehending their function in maintaining membrane potential.
Purpose of the Study:
- To characterize the ionic currents present in squid Schwann cells.
- To compare ionic currents in isolated versus in situ Schwann cells.
- To identify the specific ion channels involved in regulating Schwann cell membrane potential.
Main Methods:
- Enzymatic isolation of Schwann cells from squid giant axons (Loligo species).
- Whole-cell and patch-clamp electrophysiology (voltage clamp, single-channel recording).
- In situ electrophysiological recordings from Schwann cells within split-open axons.
Main Results:
- Two voltage-dependent currents were observed: an inward L-type calcium current and a delayed outward potassium (K+) current.
- The outward current exhibited characteristics of an outwardly rectifying K+ current, sensitive to nifedipine, Co2+, and quinine.
- Single-channel recordings revealed a K+ channel (43.6 pS conductance) sensitive to internal Ca2+ concentration.
Conclusions:
- Squid Schwann cells possess voltage-gated calcium channels and calcium-activated potassium channels.
- These channels are critical for generating and regulating the Schwann cell membrane potential.
- Resting intracellular calcium levels likely play a significant role in controlling Schwann cell membrane potential.