Schwann cell induction in the ventral portion of the spinal cord.

Schwann cell development can be induced in a predictable manner in the dorsal aspect of the lumbosacral spinal cord of the immature rat by exposing that structure to ionizing radiation. This development occurs in essentially all animals and becomes evident between 2 and 3 weeks postirradiation (P-I). Occasionally, intraspinal Schwann cells were observed ventrally at later intervals following irradiation, usually more than 45 days P-I. The present study focused on the development of Schwann cells within the ventral portion of the lumbosacral spinal cord in 53 animals followed for periods up to 7 months P-I. Ventrally located intraspinal Schwann cells developed in approximately 40% of these animals, in contrast to the development dorsally in all animals. The ventrally located aggregates were generally smaller than those dorsally and occurred more frequently in gray matter than in white matter. An interesting feature of the ventrally located Schwann cells was that they were often associated with blood vessels, which raised the possibility that these cells developed from undifferentiated cells of the vascular walls or used the vessels as a pathway for migration.