SUBCELLULAR HETEROGENEITY OF VOLTAGE-GATED CA2+ CHANNELS IN CELLS OF THE OLIGODENDROCYTE LINEAGE

We studied the distribution of voltage-gated Ca2+ channels in cells of the oligodendrocyte lineage from retinal and cortical cultures. Influ x of Ca2+ via voltage-gated channels was activated by membrane depolar ization with elevated extracellular K+ concentration ([K+](e)) and loc al, subcellular increases in cytosolic free Ca2+ concentration ([Ca2+] (i)n) could be monitored with a fluometric system connected to a laser scanning confocal microscope. In glial precursor cells from both reti na and cortex, small depolarizations (with 10 or 20 mM K+) activated C a2+ transients in processes indicating the presence of low-voltage-act ivated Ca2+ channels. Larger depolarizations (with 50 mM K+) additiona lly activated high-voltage-activated Ca2+ channels in the soma. An une ven distribution of Ca2+ channels was also observed in the mature olig odendrocytes; Ca2+ transients in processes were considerably larger. R ecovery of Ca2+ levels after the voltage-induced influx was achieved b y the activity of the plasmalemmal Ca2+ pump, while mitochondria playe d a minor role to restore Ca2+ levels after an influx through voltage- operated channels. During the development of white matter tracts, cell s of the oligodendrocyte lineage contact axons to form myelin. Neurona l activity is accompanied by increases in [K+](e); this may lead to Ca 2+ changes in the processes and the Ca2+ increase might be a signal fo r the glial precursor cell to start myelin formation. (C) 1995 Wiley-L iss, Inc.