A morphometric study on the early stages of dendrite changes in the axotomized motoneuron of the spinal cord in newborn rats

Abstract

Objectives: To study the early effect of axotomy on spinal motoneurons and dendritic trees in the newborn rat.Methods: The left sciatic nerve of 50 neonatal Sprague–Dawley rats aged 5 days old was transected and the right area kept as a control. The operated animals were killed 2, 4, 8, 12 and 24 hours after axotomy. The L4–L6 segments of the spinal cord were sampled, and stained either with Golgi-Cox or Cresyl fast violet methods. The number of motoneurons, the largest soma diameter and the different parameters of the dendritic trees such as: number, length and thickness of the primary, secondary and tertiary branches in the axotomized sides were estimated and compared statistically with that of the intact sides.Results: The results indicated that in the axotomized sides, the number of motoneurons and the largest soma diameter were decreased, but these were significant only in 12- and 24-hour groups. The number of branches of the dendritic trees including primary, secondary and tertiary branches was not significantly decreased in the groups. The thickness of the dendrites showed a reduction; however, this was significant only for the tertiary branches in the 24-hour groups. The length of the primary, secondary and tertiary branches of the dendrites—especially the latter—were also decreased significantly in most of the groups.Conclusion: Axotomy at the early stages in newborn rats resulted in noticeable morphometrical changes in motoneurons and their dendrites.