Effect of Thyrotropin-Releasing Hormone (TRH) in Experimental Spinal Cord Injury: A Quantitative Histopathologic Study

Abstract

Spinal cord injuries in rats were experimentally produced by compressing the cord (T₁₁ vertebra level) for 60 min with stainless steel screws. Morphometric analysis of the injured cord revealed that at 14 days post-injury, there were significant correlations between the neurologic score (NS) and all morphometric parameters, including total cross-sectional area (r_s = 0.438), lesioned area (r_s = -0.421) and area of the gray (r_s = 0.377) and white matter (r_s = 0.704). Although rats treated with thyrotropin-releasing hormone (TRH; 22.5 mg/kg, s.c., twice daily for 7 days starting 24 hr post-injury) showed significant improvement in NS 14 days post-injury, there were no significant differences in morphometric parameters between saline- and TRH-treated rats. In addition, no significant correlation was observed between NS and any of the morphometric parameters in TRH-treated rats, even though there was a significant correlation between the area of white matter and NS in saline-treated rats. These results suggest that neurologic recovery closely reflects the histopathological changes evident at the injury site in the present model, and that the improvement of neurologic status seen in rats with cord injury given TRH starting 24 hr post-injury is not due to protection against progression of neural damage at the injury site.