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

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.