300 Section - Circuit Mapping Identifies the Critical Role of RtTg Glutamatergic Neurons in Post-Stroke Spasticity

Post-stroke spastic movement disorder (SMD) impedes functional recovery, yet its neural mechanisms remain elusive. This study aims to establish a reliable SMD mouse model and identify key reticulospinal circuits and neuronal subtypes underlying its pathogenesis.

Design:

We employed functional magnetic resonance imaging (fMRI), polysynaptic retrograde tracing, chemogenetic manipulations, and single-cell RNA sequencing to characterize a functional reticulospinal neural circuit regulating spastic movement disorder in human and mouse models.

Results:

We found that fractional amplitude of low-frequency fluctuation (fALFF) values in the pontine reticular formation (including RtTg, PnC, and PnO) were elevated in stroke patients with motor impairment and correlated with Fugl-Meyer Assessment (FMA) and modified Ashworth scale (MAS) scores. We established a photothrombotic mouse model exhibiting spinal motor neuron hyperexcitability, where increased pontine fALFF values positively correlated with behavioral deficits and H-reflex enhancement, indicating post-ischemic excitatory remodeling. Immunofluorescence and PRV tracing revealed RtTg as a critical hub within a muscle-spinal-RtTg circuit. Single-cell RNA sequencing confirmed that increased glutamate release from RtTg glutamatergic neurons is a key mechanism, supported by immunofluorescence co-staining. Chemogenetic inhibition of this circuit effectively improved motor behavior and reduced spinal motor neuron excitability, by suppressing glutamate release from RtTg glutamatergic neurons, thereby promoting motor function recovery.


Conclusion:

Our study establishes a circuit-based framework for SMD pathogenesis, identifying RtTg glutamatergic neurons as a promising therapeutic target for post-stroke spasticity, and offering innovative circuit-based insights and a potential therapeutic target for clinical intervention.