Systemic hypothermia following spinal cord compression injury in the rat: axonal changes studied by beta-APP, ubiquitin, and PGP 9.5 immunohistochemistry

Study Design: Systemic hypothermia exerts neuroprotective effects in experi mental ischemic CNS models caused by vascular occlusions. Recent experiment al and clinical studies have also demonstrated beneficial effects of hypoth ermic treatment following brain trauma. Objectives: The present study addresses the question as to whether systemic hypothermia has similar protective qualities following severe spinal cord compression trauma using beta-APP-, ubiquitin-, and PGP-9.5-immunohistochem istry combined with the ABC complex method as markers to identify axonal ch anges. Methods: Fifteen rats were randomized into three equally large groups and s ustained to either thoracic laminectomy or to severe spinal cord compressio n trauma of the Th 8-9 segments. The non-trauma group contained laminectomi zed animals submitted to a hypothermic procedure in which the core temperat ure was reduced from 38 to 30 degrees C. The two trauma groups were either submitted to the same hypothermic procedure or kept normothermic during the corresponding time. All animals were sacrificed 24 h following the surgica l procedure. Results: In the hypothermic non-trauma group no axonal changes were seen. T he number of abnormal axons, as indicated by accumulation of immunoreactive material in enlarged axons, was lower in the peri-injury zones of the hypo thermic trauma group than in the normothermic trauma group. This difference was most obvious in the cranial peri-injury zones. No differences were see n between the groups in the trauma zones. Conclusions: This study demonstrates reduced axonal swelling in the peri-in jury zones of spinal cord injured rats treated with systemic hypothermia. T hese changes could either indicate neuroprotective effects of the hypotherm ic treatment, or be results of reduced axonal transport or. protein synthes is. To evaluate the clinical importance of our findings, further studies in cluding reliable outcome measures of the animals must be performed.