Journal of Neuroscience, Vol 2, 1292-1298, Copyright © 1982 by Society for Neuroscience
Recovery of myelination in rat optic nerve after developmental retardation by cortisol
MC Bohn and VL Friedrich Jr
Oligodendrocyte formation and myelination in the optic nerve of rats
treated with cortisol on postnatal days 7 and 18 were investigated at 21
and 60 days by autoradiographic and morphometric methods. At 21 days, the
amount of myelin in the optic nerve of treated rats was reduced by 42%.
This reduction was accompanied by a 39% decrease in the number of
myelinated axons. In addition, the myelin/axon area ratio was reduced 22%
for those axons which were myelinated. At 60 days, the amount of myelin,
the number of axons myelinated, the average axonal size, and the average
amount of myelin per axon had completely recovered to normal values.
Tritiated thymidine-labeling experiments showed that the genesis of
oligodendrocytes was enhanced following the cessation of treatment. Since
the number of oligodendrocytes in the optic nerve of treated rats was
normal at 60 days, it is suggested that the retarding effect of cortisol on
myelination in the optic nerve may be mediated, at least in part, by
inhibited formation of oligodendrocytes during treatment.