Increase in nerve growth factor-like immunoreactivity and decrease in choline acetyltransferase following contusive spinal cord injury.

We have previously described a graded spinal cord injury model in the rat. Mild contusive injury results in an initially severe functional deficit that is attenuated over time to reveal the mild chronic deficits that characterize this injury. In this study, we have shown that mild contusive injury also results in a significant decrease in choline acetyltransferase (ChAT) activity during the first week after injury. At 1 week ChAT activity is maximally reduced at the site of the contusion and is also significantly lowered throughout the spinal cord. ChAT activity then rebounds during the following 3 weeks, partially at the injury site where there is considerable loss of gray and white matter, and completely in rostral and caudal cord segments. The rebound in ChAT activity is temporally associated with the partial recovery of function. Further, the changes in ChAT activity after injury are mirrored by changes in nerve growth factor-like immunoreactivity (NGF-LI) as determined by a specific two-site ELISA. NGF-LI increases significantly after injury, reaching a maximum at 7 days after contusion and at the injury site. However, levels of NGF-LI are also significantly increased throughout the spinal cord. NGF-LI then decreases at 2 and 4 weeks as ChAT activity rebounds. Further experiments will be needed to examine the possibility of a role for NGF in promoting the recovery of function after spinal cord injury.