Remyelination in the CNS of the hypothyroid rat.

A number of studies have provided good evidence to indicate a role for thyroid hormone in myelination. Since myelination and remyelination have many shared objectives, and may therefore involve similar mechanisms, we examined whether thyroid hormone may also have a role in remyelination by both Schwann cells and oligodendrocytes of spinal cord axons that had been demyelinated by the injection of ethidium bromide in thyroidectomized rats. Neither the extent of oligodendrocyte remyelination nor the thickness of myelin sheath formed by remyelinating oligodendrocytes was affected by hypothyroidism. However, the extent of remyelination carried out by Schwann cells was decreased in hypothyroid rats compared with normal control animals.