Grant: Operating Grant

We have previously shown that cats can recover the ability to walk with the hindlimbs 2-3 weeks after a complete surgical spinal cord injury (SCI) performed at the last Thoracic spinal segment. This confirms that there exists a complex spinal circuitry capable of generating the locomotor pattern without descending brain inputs. Furthermore, during the last CIHR grant (2008-2013), we have studied the capacity of cats to walk after partial unilateral hemisection. The major finding was that cats recovered hindlimb locomotion largely through changes induced in the spinal cord (SC) below the lesion indicating its important capacity to change after lesions (neuroplasticity). We also investigated the role of locomotor training and found that it improved significantly the quality of locomotion as well as the ability to walk immediately after a complete second spinalization (instead of 2-3wks). These results have prompted us to investigate, in the present proposal, the locomotor capacity of cats after performing a more clinically relevant SC lesion using an impactor to compress the SC and damage incompletely both sides of the SC as is most often the case in humans. We will establish the kinematic and reflex changes occurring during a period of 3 weeks after the compression. In different groups of cats, we will investigate the role of important neurotransmitters such as noradrenaline and serotonin by injecting agonists or antagonists of these systems on the SC. At the end of each protocol, cats will be submitted to a terminal experiment during which we will investigate changes in the intrinsic spinal circuitry. We believe that this project has a significant clinical impact since there is virtually no kinematic nor pharmacological studies in cats with contusive lesions and this is needed to establish an appropriate pharmacotherapy in humans with SCI.