Scientists are investigating various avenues for treatment of spinal cord injury. Therapeutic research is focused on two main areas: neuroprotection and neuroregeneration. The former seeks to prevent the harm that occurs from secondary injury in the minutes to weeks following the insult, and the latter aims to reconnect the broken circuits in the spinal cord to allow function to return. Neuroprotective drugs target secondary injury effects including inflammation, damage by free radicals, excitotoxicity (neuronal damage by excessive glutamate signaling), and apoptosis (cell suicide). Several potentially neuroprotective agents that target pathways like these are under investigation in human clinical trials.