POTASSIUM CHANNEL-DEPENDENT CHANGES IN THE VOLUME OF DEVELOPING MOUSE SCHWANN-CELLS

Physiological roles of voltage-gated K+ channels in developing mouse Schwann cells were investigated using whole-cell variation of the patch-clamp technique. In neonatal myelin-associated Schwann cells, local cytoplasmic swellings were induced when membrane potential (MP) was kept more negative than zero-current potential (membrane hyperpolarization) and they decreased in sizes when MP was kept positive. A lack of changes of cytoplasmic volume in Schwann cells of 17- to 18-day-old embryos or in neonatal myelin-associated cells in a solution containing Ba2+ suggested that activation of Ba2+-sensitive K+ channels caused cytoplasmic volume changes. Significant increase in magnitudes of Ba2+-sensitive K+ currents in neonatal myelin-associated cells after membrane hyperpolarization suggested. that these K+ channels locate in adaxonal Schwann cell membrane and probably determine the sites of Schmidt-Lanterman incisures.