TRANSIENT DECREASE OF ACETYLCHOLINESTERASE IN VENTRAL HORN NEURONS CAUDAL TO A LOW THORACIC SPINAL-CORD HEMISECTION IN THE ADULT-RAT

Light microscopic enzyme histochemistry was employed to study the alte rations of acetylcholinesterase (AChE) within lumbosacral ventral horn neurons at survival times of 1, 4, 7, 14, 28, 60, and 90 days after l ow thoracic spinal cord hemisection in adult rats. The intensity of hi stochemical staining was quantified using densitometric techniques. Vi rtually all ventral horn neurons of sham-operated and unoperated anima ls, which served as controls, displayed intense AChE staining. Hemisec tion of the spinal cord induced a transient, ipsilateral decrease of A ChE staining in most neuronal cell bodies and in the neuropil of lamin a IX at all segmental levels caudal to the lesion. Quantitative analys is of representative segments revealed a reduction of AChE in the vent ral horn during a postoperative (p.o.) period of 1 to 28 days followed by a phase of recovery over the next two months. AChE activity still remained slightly reduced, even at 90 days p.o. The transient decrease in AChE is a well-known metabolic response of axotomized motoneurons. However: the observed changes of AChE reactivity in intact motoneuron s ipsilateral and caudal to the hemisection are presumably induced by the interruption of supraspinal descending pathways, These metabolic c hanges may functionally affect the whole motor unit and be involved in the disturbances of motor function following spinal cord injury.