Manual therapy ameliorates neuromuscular dysfunction in spastic model rat: involvement of the C-Fiber-mediated CaMKII pathway

Background: This study investigated whether manual therapy applied to tendon organs ameliorated neuromuscular dysfunction in rats with spasticity induced by upper motor neuron injury associated with spastic cerebral palsy, and analyzed the potential involvement of the C-fiber-mediated CaMKII signaling pathway. Methods: Male rats were used to establish palsy models and divided into groups: Control, Model, Manual Therapy (MT), Capsaicin Treatment, Sham, CaMKII Inhibitor, and DMSO Solvent groups. Except for Control, all underwent pyramidal-tract destruction. After modeling, the MT group received manual therapy on the left-lower leg tendon organs. The Capsaicin group underwent sciatic nerve capsaicin treatment for C-fiber block on days 2 and 7; the Sham group had sciatic nerve exposure only. Both received daily manual therapy intervention for 14 days. The CaMKII Inhibitor and DMSO Solvent groups received intrathecal injections every 2 days (7 times total) without manual intervention. Spasticity-related behavioral indices, molecular expression, and neurotransmitter levels were assessed. Results: Manual therapy reduced the neurological deficit scores and muscle spasticity scores of model rats, improved the pathological morphology of the pyramidal tract and skeletal muscle, and regulated the expression of key molecules and neurotransmitters in the spinal cord and hippocampus. The therapeutic effects of manual therapy were significantly attenuated after C-fiber blockage, and although CaMKII inhibition could partially mimic the neuromodulatory effects of manual therapy, its efficacy in alleviating spasticity was inferior to that of manual-therapy intervention. Conclusion: Manual therapy appears to regulate CaMKII signaling via C-fiber afferent pathways to ameliorate neuromuscular dysfunction in a rat model of spasticity induced by pyramidal-tract lesion, thereby providing experimental evidence for the clinical application of optimized manual therapy parameters in the management of spasticity in patients with cerebral palsy.