CHANGES IN CHOLINE-ACETYLTRANSFERASE ACTIVITY AND DISTRIBUTION FOLLOWING INCOMPLETE CERVICAL SPINAL-CORD INJURY IN THE RAT

Incomplete cervical spinal cord injuries were produced in rats by plac ing 10 g or 20 g weight on exposed dura at the C6 level for 5 min (Mil d or Moderate injury). These two degrees of the injury resulted in ini tial motor functional deficits, followed by recoveries. In this study, changes in choline acetyltransferase activity and distribution follow ing the incomplete cervical cord injuries were investigated using radi oenzyme assay, and fluorescence microphotometry. We demonstrated that mild injury led to a transient decrease of choline acetyltransferase a ctivity in the compressed spinal cord segment, bur showed almost no hi stologic change al two days after injury. Although a low level of chol ine acetyltransferase immunofluorescence was found in the ventrolatera l anterior horn at two days after injury, it recovered completely by o ne week after injury. These findings suggest that there was a strong c orrelation between the transient motor functional deficit and the decr ease in choline acetyltransferase activity following mild injury. Mode rate injury resulted in a persistent low level of choline acetyltransf erase activity in the compressed spinal cord segment accompanied by a striking loss of gray matter. On the other hand, al seven, 14 and 28 d ays after injury, over-expression of choline acetyltransferase activit y was found in the neighboring spinal cord segments located both rostr al and caudal to the injury, which showed no histologic change. In add ition, excessively high levels of choline acetyltransferase immunofluo rescence were Found in the ventrolateral anterior horn of these segmen ts. A strong correlation was found between the motor functional recove ry and the late, excessive high levels of choline acetyltransferase ac tivity in the neighboring regions. These results suggest that choliner gic neurons, especially spinal motor neurons may play an important rol e in the motor functional recovery following incomplete cervical spina l cord injury. Copyright (C) 1996 IBRO.