Neuroglial population in the spinal white matter of neonatal and early postnatal rats: an autoradiographic study of numbers of neuroglia and changes in their proliferative activity.

Abstract

AbstractThe temporal pattern of increase in number of neuroglia in spinal cord white matter and the amount of multiplication in situ of these cells were studied in rats ranging from less than 12 hours following birth to 30 days of age. Autoradiographs of sections from animals killed four hours after injection of tritiated thymidine were studied; counts of the total neuroglial population and of the number of labeled neuroglia were made in the white matter of each half of the cord (hemisection). During the first two weeks following birth, the number of neuroglia per hemisection increased six times; thereafter, the population appeared to be stable. The increases in number of labeled neuroglia appeared to parallel the rise in total population, particularly during the period of greatest population increase, i.e., days 7 through 12. After 12 days, when the total population stabilized, there was a marked and rapid decrease in the number of labeled cells. The walls of the central canal were examined in view of the role this area plays in the initial development of the nervous system. In rats killed during the first 14 days postnatally, the dorsal and ventral walls were incomplete; however, numerous, unidentified cells adjacent to these walls were oriented as if entering the dorsal median septum and the ventral median sulcus. By 22 days the central canal area had more of its adult appearance.