Project Summary/Abstract The goal of this project is to study the 5-hydroxytryptamine 1F receptor in stimulating mitochondrial biogenesis (MB) and recovery from spinal cord injury (SCI). SCI is a devastating disorder without meaningful treatment. SCI is defined by direct trauma to the spinal cord, which disrupts the vasculature, leading to decreased oxygen delivery within the injured area and reducing the ability of mitochondria to maintain cellular energetics. Studies investigating mitochondria as a therapeutic target for SCI have only addressed individual aspects of mitochondrial function. Therapeutics pursuing reestablishment of mitochondrial homeostasis through increased mitochondrial biogenesis (MB) following SCI could alleviate multiple facets of injury progression. Our MB drug discovery program identified the 5-HT1F receptor agonist LY344864 as a specific and potent inducer of MB in mice. The 5-HT1F receptor is a lesser-studied 5-HT receptor found in the CNS and peripheral tissues. Lasmiditan is a potent and specific 5-HT1F receptor agonist that is in phase III clinical trials for migraine headaches. Our preliminary studies revealed that treatment with either LY344864 or lasmiditan improved mitochondrial function, locomotion and blood spinal cord barrier (BSCB) integrity as early as 7 d post-SCI. Locomotor capability further improved through 21 d. While similar efficacy of both agonists was observed when administration was initiated 1 or 8 h after injury, lasmiditan was 20-fold more potent than LY344864 (0.1 vs 2 mg/kg). Exposure to either compound induced MB in primary cultures of mouse cerebral microvascular endothelial cells, lasmiditan being 10 times more potent than LY344864 (3 vs 30 nM). Therefore, we hypothesize that treatment with lasmiditan following SCI will increase MB, resulting in improved locomotor recovery, decreased neuronal death and increased vascular repair post-SCI. We will test this hypothesis in the following Specific Aims. Aim 1 will determine MB, locomotor capability and lesion volume in response to lasmiditan treatment post-SCI in mice. Aim 2 will determine vascular recovery and BSCB integrity in response to lasmiditan post-SCI in mice. Aim 3 will determine MB, regenerative capacity and 5-HT1F receptor signaling pathway in response to LY344864/lasmiditan under normal and injured conditions in mouse cerebral endothelial cells (MCEC).