The Effect of Hyperbaric Oxygen Therapy on Fos Expression in Rat Spinal Cord Neurons Following Spinal Cord Injury

Objectives: We investigated the effect of hyperbaric oxygen (HBO) therapy on Fos protein expression in spinal cord neurons in rats following spinal cord injury (SCI). Methods: Rivlin and Tator clip method was used to produce SCI at T9-T11 in Sprague-Dawley rats (n=16) divided into four groups. 1. Control (SCI, no HBO), 2. Preoperative HBO (HBO five days before SCI), 3. Postoperative HBO (HBO just after SCI for five days), 4. Pre- and postoperative HBO (HBO five days before SCI and after SCI for five days). Rats received HBO at 2.80 ATA 60 min daily. Results: Fos immunohistochemistry was used to localize neurons following SCI and HBO therapy in spinal cord segments 1 cm proximal and 1 cm distal to SCI. HBO applied preoperatively, postoperatively and pre- and postoperatively significantly increased Fos expression in the spinal cord. The increase corresponded with the duration of HBO therapy. In all groups, Fos expression was mostly in laminae 1-2, followed by 3-4, and 7-8. This is the first study showing the effect of HBO therapy on Fos expression in rats with SCI. Conclusion: Nitric oxide is involved in nociception. In this study, we expected a decrease in Fos following HBO therapy in SCI accordingly; however, this was not the case, suggesting the increase in Fos is not related to pain, but possibly to mechanisms related to neuroprotection.