Spinal cord injury (SCI) causes significant sensorimotor deficits that negatively impact autonomy and quality-of-life. In a previous study, we determined that optogenetic spinal stimulation significantly enhanced forelimb recovery, axonal growth, and angiogenesis compared to sham controls. However, we have yet to determine the synaptic changes associated with optogenetic stimulation after SCI. The current project addresses this important detail by quantifying the synaptic changes that occur with and without optogenetic spinal stimulation in rats with cervical SCI.To investigate this, rats received a moderate hemicontusion of the 4th cervical segment (C4) and a spinal injection of an optogenetic viral vector (AAV2-hSyn-ChR2-YFP) to express light-sensitive proteins in the ipsilateral sixth segment (C6). Four weeks later, rats received a second surgery to receive a blue uLED implanted over ipsilateral C6 for optogenetic or sham stimulation. Rats were trained and scored regularly on a variety of forelimb behavioral tasks throughout the course of the study, while the rats in the stimulated group received stimulation 1x/week for 6 weeks beginning on the 6th week post-injury. After perfusion, the cervical spinal cord was sectioned and underwent immunohistochemistry (IHC) staining to examine synaptic density around motoneurons caudal to the lesion site where stimulation or sham stimulation occurred. Synaptic quantification has been completed using FIJI software. Our initial results reveal increased synaptic density around the motoneurons of rats that received optogenetic spinal stimulation, suggesting an increase in synaptic plasticity and connectivity. This indicates that stimulation not only enhances axonal growth but also supports the formation of new connections with downstream neurons partially disconnected by the injury. This study provides insight into the circuitry-related changes involved in SCI recovery. Identifying specific mechanisms of how optogenetic stimulation improves recovery can guide the development of more effective stimulation paradigms and treatment strategies in order to optimize functional recovery for people with spinal cord injury