The percentage of surviving motor neurons in the ventral horn of the C6 spinal segment ((lesioned side/unlesioned side) × 100) at 28 days after injury. Group A and C rats showed significantly lower numbers of surviving motor neurons than group B and D rats (*P < 0.0001). Group B rats showed a significantly lower number of surviving motor neurons than group D rats (*P < 0.0001). There was no significant difference between group A and C rats (P = 0.30). All data are expressed as mean ± SD.