Fig. 1.

Tetrodotoxin (TTX) inhibits the onset of myelination A, Co-cultures of neurons and oligodendrocyte progenitors were established from cereberal hemispheres of 15-day-old mouse fetuses TTX (10⁻⁶ M) was added to the culture medium at 8 days in vitro (DIV) and maintained for 2 or 4 days, as indicated Cultures at 18 to 21 DIV were immunolabeled with an anti-myelin basic protein (MBP) antibody The total number of MBP + myelinated mternodes per coverslip was determined Values are the mean ± SEM of 8 different experiments Significant differences between control specimens and TTX-treated samples are indicated **, P < 0.02 two tailed unpaired Student’s t-test. B, An intraocular injection of TTX was performed in 4-day-old (P4) mice and the number of myelin-forming MBP+ oligodendrocytes as seen by epifluorescence microscopy m whole mounts of optic nerve were evaluated at P6. The total number of myelin-forming MBP+ cells was determined in TTX-treated and sham-injected control optic nerves, from the emergence of the optic canal to the optic chiasm Results obtained in 12 sham and 10 TTX-injected animals (four separate experiments) are expressed as the mean ± SEM, and significant differences between control specimens and TTX-treated samples are indicated :*, P < 0 05, two-tailed unpaired Student’s t-test) (Modified from Demerens C, Stankoff B, Logak M, Anglade P, Allinquant B, Couraud F, et al Induction of myelination in the central nervous system by electrical activity Proc Natl Acad Sci U S A 1996,93 9887-92. Copynght © 1996 the National Academy of Sciences, U.S.A. Used with permission.)