SPINAL MOTONEURON DENDRITIC ALTERATION AFTER SPINAL-CORD HEMISECTION IN THE RAT

Alteration of spinal motoneurons can be induced by axotomy, deafferentation, or deafferentation of spinal interneurons. Dendritic profiles of rat lamina IX motoneurons were studied 1.5-2.5 mm rostral to a [thoracic] T2, T3 (interface) hemisection [6 per group of normal, 7-, 14-, 30-, 60-, and 90-day postoperative (DPO) animals]. The spinal cord was impregnated using the Golgi technique and individual dendritic segments measured from coded slides, the data were computerized, and the length, number of segments, and dendritic profile were reconstructed. These data were heteroscedastic (.alpha. < 0.005) making them inappropriate for ANOVA [analysis of variance]. The data did show 2 size classes of motoneurons at 14, 30, 60 and 90 DPO. At 7 DPO, there was a reduced dendritic field. At 14-60 DPO, there were gigantic motoneurons that were many times larger than normal or other neurons in these operated groups. At 90 DPO a large motoneuron was present. Individual motoneurons have different regenerative dendritic response after spinal injury.