Tehran University of Medical Sciences Acta Medica Iranica 0044-6025 51 7 2013 07 15 431 437 EN Seyed Behzad Jazayeri Sina Trauma and Surgery Research Center, Tehran University of Medical Sciences, Tehran, Iran. AND Student’s Scientific Research Center, Tehran University of Medical Sciences, Tehran, Iran. Masoumeh Firouzi Tissue Repair Laboratory, Institute of Biochemistry and Biophysics (IBB), Tehran University of Medical Sciences, Tehran, Iran. Shayan Abdollah Zadegan Sina Trauma and Surgery Research Center, Tehran University of Medical Sciences, Tehran, Iran. AND Research Centre for Neural Repair, Tehran University of Medical Sciences, Tehran, Iran. Niloufar Saeedi Sina Trauma and Surgery Research Center, Tehran University of Medical Sciences, Tehran, Iran. Elham Pirouz Sina Trauma and Surgery Research Center, Tehran University of Medical Sciences, Tehran, Iran. Mohsen Nategh Research Centre for Neural Repair, Tehran University of Medical Sciences, Tehran, Iran. Issa Jahanzad Department of Pathology, Faculty of Medicine, Tehran University of Medical Sciences, Tehran, Iran. Ahmad Mohebbi Ashtiani Research Centre for Neural Repair, Tehran University of Medical Sciences, Tehran, Iran. Vafa Rahimi-Movaghar Sina Trauma and Surgery Research Center, Tehran University of Medical Sciences, Tehran, Iran. AND Research Centre for Neural Repair, Tehran University of Medical Sciences, Tehran, Iran. 2015 10 11 Prior animal models have shown that rats sustaining 3-second immediate spinal cord compression had significantly better functional recovery and smaller lesion volumes than rats subjected to compression times of 1 hour, 6 hours, 3 weeks, and 10 weeks after spinal cord injury. We compare locomotor rating scales and spinal cord histopathology after 3 seconds and 10 minute compression times. . Ten rats were assigned into two early (3-second) and late (10-minute) compressive surgery groups. Compressive injury was produced using an aneurysmal clip method. Rats were followed-up for 11 weeks, and behavioral assessment was done by inclined plane test and tail-flick reflex. At the end of the study, the rats were sacrificed, and spinal cord specimens were studied in light and EM. Basso, Beattie and Bresnahan (BBB) locomotor rating scales were significantly better in the early compression group after the 4th week of evaluation (P<0.05) and persisted throughout the remainder of the study. Histopathology demonstrated decreased normal tissue, more severe gliosis and cystic formation in the late group compared to the early group (P<0.05). In EM study, injuries in the late group including injury to the myelin and axon were more severe than the early compression group, and there was more cytoplasmic edema in the late compression group. Spinal cord injury secondary to 3-second compression improves functional motor recovery, spares more functional tissue, and is associated with less intracellular edema, less myelin and axon damage and more myelin regeneration in rats compared to those with 10 minutes of compression. Inclined plane test and tail-flick reflex had no significant difference. https://acta.tums.ac.ir/index.php/acta/article/view/4416 https://acta.tums.ac.ir/index.php/acta/article/download/4416/4581