Pontine norepinephrine content after motor cortical ablation in rats.

It has been reported that norepinephrine (NE) plays an important role in recovery after brain damage. However, the role of the pons, the site where the norepinephrinergic locus coeruleus (LC) is located, has not been elucidated. In order to study the changes in the pontine NE content in either noninjured, injured or recovered rats, we used 35 animals trained to walk across to a walkway where their footprints were recorded. Subsequently, 17 trained rats were sham-operated while 18 were injured by means of an ablation of the right motor cortex representative of the hindlimb. From the injured rats, 6 were sacrificed 6 hr before surgery in order to obtain the pons, while all the remaining rats were recorded in the walkway 6, 24 and 48 hr post-surgery. Then, rats were sacrificed by decapitation, the pons was removed and each hemisphere was prepared for the chromatographic analysis of NE. Results showed that after cortical brain damage, the length of the stride decreased while the angle of the stride increased 6 hr post-surgery. Recovery was observed after 24 hr. NE increased in the pons after 6 hr and returned to normal levels when rats had recovered. This suggests that cortical damage elicits NE changes in the LC that could reorganize the system to lead the recovery process. Such findings must be taken in account when pharmacotherapy with antidepressants or antipsychotics that act on norepinephrine-containing neuronal systems are prescribed in patients after stroke.