Effects of methylprednisolone and MK-801 on functional recovery after experimental chronic spinal cord injury

Study design: An experimental study was conducted to evaluate the effects o f methylprednisolone and MK-801 after the compressive injury of spinal cord in rats. Objectives: To investigate the effect of methylprednisolone and non-competi tive NMDA antagonist MK-801 in long-term functional outcome after spinal co rd injury (SCI). Methods: A randomized group A of Sprague-Dawley rats were treated with MK-8 01 (1.0 mg/kg, n=10; Group A) after a compression injury. A group of methyl prednisolone (MP)-treated (30 mg/kg, n=10; Group B) and non-treated animals (n=9; Group C) were included for comparison. The functional motor outcome such as inclined plane (IP), toe spreading reflex (TSR), and modified Tarlo v scale (TS) were measured in each animal at regular time points up to 8 we eks post-treatment. Histologically the injury site was scored in four group s and immunohistochemically Wallerian Degeneration (WD), astrocytosis and e xpression of beta -amyloid protein was identified. Results: In examining the IP data, no significant difference was recognized between the group means (P-value > 0.5). For the TSR, there were no differ ences in the group responses. For the TS, the differences were not statisti cally significant. Only group B showed significance in cavitation scores co mpared to group A (P > 0.0094), WD was significantly different than group C (P > 0.03), astrocytosis was significantly higher than group A (P > 0.001) and modest presence of beta -amyloid protein. Conclusion: Our data indicate that one time bolus administration of MK-801 lacks any significant effect on axonal function in chronically injured rats . Daily bolus administration of MP at 30 mg/kg also did not ensure a better functional outcome. Immunohistochemically we have been able to show signif icant differences in WD, astrocytosis and small insignificant changes in be ta -amyloid protein.