[Changes in noradrenergic neurons in the rat spinal cord after brain injury]

To investigate the impact of experimental brain injury on the noradrenergic (NA) neurons in the spinal cord, in order to explore possible mechanism of the changes in NA neuron expression.

Seventy healthy Wistar rats were randomly divided into two groups: normal group (n=10), brain injury (BI) group (n=60). The animals in BI group were subjected to BI with the modified Feeney's method. The spinal cords of rats were harvested at 3, 6, 12, 24, 48 and 72 hours after the injury, respectively. Immunohistochemistry (IHC) and reverse transcriptase-polymerase chain reaction (RT-PCR) were used to assess the changes in dopamine-beta-hydroxylase (DBH) expression.

IHC showed a small number of DBH-positive neurons distributed in anterior horn of the cervical and lumbar enlargements in control group; a larger number of dark-stained noradrenergic neurons were found in anterior horn, and also in posterior and lateral horns of spinal cord in brain injury group at different time points after injury, as compared with control group (P<0.05 or P<0.01). RT-PCR showed that the expression of DBH mRNA in brain injury group was significantly higher than that in control group at different time points after injury (P<0.05 or P<0.01).

A significant increase of NA neurons in spinal cord of brain injury group suggests that more NA is synthesized by the neurons, which is necessary to meet the demand of the organism under the stress condition, suggesting that NA plays a very important role in the course of brain injury.