Degeneration and regeneration of motoneuron dendrites after ventral root crush: Computer reconstruction of dendritic fields

Dendritic alteration can be induced by peripheral axotomy of central nervous system neurons. In the following experiment the dendritic profile of rat lamina IX motoneurons in the spinal cord segment under the T2 vertebra after ventral root crush (controls, 14, 30, 60, and 90 days postoperative (DPO), six animals per group) were studied. The spinal cord was impregnated by the Golgi technique, individual dendritic segments were measured from coded slides, the data computerized, and the dendrites reconstructed by computer. The dendritic parameters generated were length of the dendritic segment between branches, total number of branches, number of terminal branches, and serpentine length (total length of entire dendrite). Inter- and intraanimal statistical comparisons were made by ANOVA a priori and the Newman-Keuls test a posteriori. There were statistically significant losses and gains of dendritic branches and numbers of terminal dendrites (lowest, 14 and 60 days; highest, 30 and 90 days). The serpentine length of the dendrites showed the same statistically significant oscillations. There were statistically significant differences in average dendritic parameters (calculated from distance along dendritic segments) after ventral root crush. However, 17% of the neurons at 14 days, 100% at 30 days, 33% at 60 days, and 17% at 90 days differed from control values in serpentine length and at 14 DPO, 50%; 30 DPO, 50%; 60 DPO, 67%; and 90 DPO, 70% of the neurons had numbers of dendritic segments different from control. These data show that there is a cyclic degeneration and regeneration of motoneuron dendrites after ventral root crush for at least 90 postoperative days.