Identification of the Avulsion-Injured Spinal Motoneurons

Abstract In laboratory studies, counting the spinal motoneu-rons that survived axonal injury is a major method to estimate the severity and regenerative capacity of the injured motoneu-rons after the axonal injury and rehabilitation surgery. How-ever, the typical motoneuron marker, the choline acetyltrans-ferase (ChAT), could not be detected in the injured motoneu-rons within the first 3–4 weeks postinjury. It is necessary to explore the useful and reliable specific phenotypic markers to assess the fate of injured motoneurons in axonal injury. Here, we used the fluorogold to retrograde trace the injured moto-neurons in the spinal cord and studied the expression patterns of the alpha-motoneuron marker, the neuronal nuclei DNA-binding protein (NeuN) and the peripheral nerve injury mark-er, the activating transcriptional factor (ATF-3), and the oxi-dative stress marker, the neuronal nitric oxide synthase (nNOS) within the first 4 weeks of the root avulsion of the right brachial plexus (BPRA) in the adult male Sprague-Dawley rats. Our results showed that ATF-3 was rapidly induced and sustained to express only in the nuclei of the fluorogold-labeled injured motoneurons but none in the unaf-fected motoneurons from the 24 h of the injury; meanwhile, the NeuN almost disappeared in the avulsion-affected moto-neurons within the first 4 weeks. The nNOS was not detected in the motoneurons until the second week of the injury. On the basis of the present data, we suggest that ATF-3 labels avulsion-injured motoneurons while NeuN and nNOS are poor markers within the first 4 weeks of BPRA