5-HT1A Antagonist WAY-100635 Prevents Chronic Neurodegeneration and Immune Activation After TBI

Traumatic brain injury (TBI) initiates secondary neurodegeneration that compromises interconnected neural circuits and contributes to persistent visual and neurobehavioral impairment. Pharmacological strategies that preserve vulnerable neurons and synapses while limiting chronic neuroinflammation remain an unmet therapeutic need. We previously identified the serotonin 1A receptor (5-HT1A) antagonist WAY-100635 through screening human stem cell-derived retinal ganglion cells (RGCs) and demonstrated that it promotes neuroprotection through cyclic adenosine monophosphate-dependent mitochondrial biogenesis. Here, we investigated whether post-injury treatment extends this neuroprotective efficacy to cerebral and visual circuitry following TBI. Male C57BL/6J mice aged 2-3 months underwent unilateral controlled cortical impact (CCI) involving the left visual cortex. Mice were randomly assigned to sham, untreated injury or treated injury groups, with 3-10 sham controls and 5-8 mice per injury group across experiments. WAY-100635 was administered intraperitoneally at 5 mg/kg daily, beginning 1 hour after injury and continuing for 6 weeks. Therapeutic efficacy was assessed using motor and psychological-health-relevant risk-taking/behavioral disinhibition by elevated-plus-maze assessment, visual electrophysiology, optokinetic responses, diffusion magnetic resonance imaging, and retinal and cortical histopathology. Unilateral cortical injury produced bilateral RGC dysfunction and loss, with greater degeneration in the eye contralateral to the injured hemisphere, consistent with predominantly crossed murine visual projections. WAY-100635 significantly preserved RGC survival and function, improved visual acuity and contrast sensitivity, and preserved visually evoked cortical responses to contralateral eye stimulation. Diffusion MRI revealed bilateral visual pathway abnormalities, with treatment selectively normalizing fractional anisotropy and radial kurtosis in the optic tract ipsilateral to cortical injury. In perilesional cortex, treatment preserved neuronal cell bodies and synapses detected by synaptophysin immunoreactivity while markedly reducing microglial/macrophage activation and reactive astrogliosis. These effects were accompanied by improved early motor performance and attenuation of injury-associated increases in open-arm exploration in the elevated plus maze. Cortical cavity volume was not significantly reduced, supporting preferential protection of vulnerable circuitry surrounding and connected to the primary lesion. These findings identify post-injury WAY-100635 treatment as a novel therapeutic intervention that combines neuronal and synaptic preservation with reduced chronic glial activation and improved functional outcomes. They support further translational development of serotonin 1A receptor antagonism to limit secondary neurodegeneration and the visual and neurobehavioral consequences of TBI.