Characteristics of Na+ current in Schwann cells cultured from frog sciatic nerve

✍ Scribed by T. Miyazaki; J. Tasaka; S. Sakai; T. Hashiguchi; A. L. Padjen; T. Tosaka

• Publisher: John Wiley and Sons
• Year: 1994
• Tongue: English
• Weight: 832 KB
• Volume: 10
• Category: Article
• ISSN: 0894-1491
• DOI: 10.1002/glia.440100406

✦ Synopsis

Characteristics of voltage-dependent currents in cultured frog Schwann cells were investigated by the whole-cell clamp technique. An inward current was detectable a t a membrane potential level more positive than -50 mV and reached a maximum value at about -10 mV, while no rectifying channel was present. The inward current was carried by Na' ions, because the extrapolated reversal potential of the current agreed with the calculated ENa, and the current was sensitive to tetrodotoxin. The membrane potential for half-maximal inactivation was -82 mV. The inactivation curve indicated that more than 90% of the Na' channels were inactivated a t the resting membrane potential, suggesting that the cultured frog Schwann cells could not generate an action potential under physiological conditions. The time constant for the inactivation a t a maximum current was 5.3 ms ( -10 mV, 13°C).

The electrophysiological characteristics of the Na' current in the cultured frog Schwann cells were compared with those in other tissues. This Na' current was quantitatively different from that observed in the amphibian node of Ranvier but was similar to that in the mammalian Schwann or glial cells, especially in the more hyperpolarized halfmaximal inactivation potential and in the slower inactivation time course.