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.