INDUCTION OF MYELINATION IN THE CENTRAL-NERVOUS-SYSTEM BY ELECTRICAL-ACTIVITY

The oligodendrocyte is the myelin-forming cell in the central nervous system. Despite the close interaction between axons and oligodendrocyt es, there is little evidence that neurons influence myelinogenesis. On the contrary, newly differentiated oligodendrocytes, which mature in culture in the total absence of neurons, synthesize the myelin-specifi c constituents of oligodendrocytes differentiated in vivo and even for m myelin-like figures. Neuronal electrical activity may be required, h owever, for the appropriate formation of the myelin sheath. To investi gate the role of electrical activity on myelin formation, we have used highly specific neurotoxins, which can either block (tetrodotoxin) or increase (alpha-scorpion toxin) the firing of neurons. We show that m yelination can be inhibited by blocking the action potential of neighb oring axons or enhanced by increasing their electrical activity, clear ly linking neuronal electrical activity to myelinogenesis.