After a spinal cord injury the brain is no longer completely in control of the body below the level of injury. This affects many organs and systems in the body, we are interested in understanding how a spinal cord injury affects blood pressure and blood flow to the brain. We are going to study blood pressure while the person is seated in a wheelchair before and after we give the subject medications which should increase blood pressure in a laboratory setting and over the course of a normal day in persons with spinal cord injury.