Comparison of thyrotropin‐releasing hormone (TRH), naloxone, and dexamethasone treatments in experimental spinal injury

Abstract

We have shown that early treatment with either naloxone or thyrotropin-releasing hormone (TRH) significantly improves neurologic outcome after experimental spinal injury. Because these previous studies used different injury variables, no conclusion could be made about the relative effectiveness of the two drugs. In the present study naloxone and TRH treatment (each 2 mg per kilogram bolus, 2 mg per kilogram per hour for 4 hours) were directly compared; other cats received either dexamethasone (0.5 mg per kilogram bolus, 0.5 mg per kilogram per hour) or saline. The spinal cord was traumatized at C-7, using the Allen method; treatment was begun 1 hour after injury. Neurologic function was graded between 0 and 10, using an ordinal rating scale. Both TRH- and naloxone-treated animals had significantly better functional scores than saline controls at 6 weeks postinjury. Moreover, TRH-treated cats also showed significantly better neurologic recovery than either naloxone- or dexamethasone-treated animals. These findings confirm the therapeutic benefit of TRH and naloxone in experimental spinal injury and indicate that TRH treatment is most effective. In contrast, corticosteroid treatment was of no benefit in the present model.