Transplantation of neuronal precursors into the central nervous system offers great promise for the treatment of neurological disorders including spinal cord injury (SCI). Among the most significant consequences of SCI are bladder spasticity and neuropathic pain, both of which likely result from a reduction in those spinal inhibitory mechanisms that are essential for normal bladder and sensory functions. Our preliminary data show that embryonic inhibitory neuron precursor cells integrate in the adult nervous system and increase inhibitory network activity. Therefore inhibitory nerve cell transplants could be a powerful way to establish new inhibitory circuits in the injured spinal cord that will reduce bladder spasticity and attenuate central neuropathic pain. We already have proof-of-principle data that murine inhibitory nerve cells integrate in the adult spinal cord and improve symptoms in an animal model of chronic spinal cord injury. We have also recently developed methods to create human inhibitory interneurons from embryonic stem cells. This proposal will capitalize on these recent developments and determine whether our human embryonic stem cell-derived inhibitory cells can be successfully transplanted into the grey matter of the injured spinal cord and reduce neurogenic bladder dysfunction and neuropathic pain, two major causes of suffering in chronic SCI patients. If successful, our studies will lay the groundwork for a potential novel therapy for chronic SCI.