CENTRAL DEMYELINATION INDUCED IN-VIVO BY THE CALCIUM IONOPHORE IONOMYCIN

The effects of injecting the calcium-selective ionophore, ionomycin, i nto myelinated tracts in the dorsal columns of adult rat spinal cords were examined electron microscopically. In vivo, ionomycin induced a p rimary vesicular demyelination, together with a variable degree of axo nal degeneration, in a dose-dependent manner The results are consisten t with previous demonstrations that mature oligodendrocytes are more v ulnerable to alterations in levels of [Ca2+](i) than other glial cells . We speculate that demyelination induced by ionomycin in vivo occurs as a result of direct activation of endogenous Ca2+-dependent enzymes and/or as a consequence of oligodendrocyte injury mediated via astrocy tes.