Induction of immediate early gene (IEG) expression is believed to constitute one of the earliest steps in plasticity and long-term modification of neuronal properties. Although behavioral evidence of neuronal plasticity at the sublesional level after spinal cord injury exists, spatiotemporal changes of IEGs in spinal segments located caudally to such an injury have never been examined. Here, the authors studied spatiotemporal changes of c-fos, nor-1, nur77, nurr1, and retinoid x receptor (rxr) messenger RNA expression in the lumbar segments L1-L2 after low-thoracic spinal transection (Tx). C-fos expression generally increased in the dorsal horn with significant levels reached at 3 days and 14 days post-Tx. Basal nor-1 transcript levels decreased in the intermediate zone and dorsal horn areas at 7 days. Nur77 levels were nonsignificantly depressed throughout that period of time, whereas nurr1 and rxr transcripts were not detected before or after Tx. In conclusion, the results provide evidence of distinct roles for c-fos and nor-1 in reorganization and plasticity of neuronal networks typically involved in sensorimotor integration and locomotor control.
Study design: Literature review. Objective: To describe quantitatively some of most important anatomic, systemic, and metabolic changes occurring soon (one month) after spinal cord trauma in mice. Setting: University Laval Medical Center. Results: Significant changes in weight, mechanical and contractile muscle properties, bone histomorphometry and biomechanics, deep-vein morphology, complete blood count, immune cell count, lipid metabolism and anabolic hormone levels were found occurring within 1 month in completely spinal cord transected (Th9/10) mice. Conclusion: These data reveal that many changes in mice and humans are comparable suggesting, in turn, that this model may be a valuable tool for neuroscientists to investigate the specific mechanisms associated with rapid health degradation post-SCI.
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