ABSTRACT
Spinal cord stimulation (SCS) is an established therapy for neuropathic pain, typically delivered at either low (60 Hz) or high (1 kHz) frequencies, with analgesic effects largely dependent on active stimulation. Here, we investigated whether combined-frequency SCS produces sustained analgesia beyond stimulation periods and explored the underlying mechanisms. Using a spared nerve injury (SNI) model in both rats and mice, we applied dual-frequency SCS (60 Hz + 1 kHz). This paradigm produced robust reversal of mechanical allodynia during stimulation and, notably, a progressive and long-lasting analgesic effect that persisted for days to weeks after stimulation cessation. RNA sequencing revealed pronounced immune-related transcriptional changes in the spinal cord, including upregulation of innate immune, pro-resolution, and neutrophil-associated pathways. Functional studies demonstrated that neutrophil depletion attenuated SCS-induced analgesia, whereas intrathecal S100A8 treatment mimicked therapeutic effects via CD69/SOCS3 signaling. These findings identify dual-frequency SCS as a promising strategy to prolong analgesia and highlight a critical role for neuroimmune modulation in sustained pain relief.
Highlights
Combined-frequency, not single-frequency SCS, sustains analgesia during washout
Combination SCS induces robust immune activation in spinal cord and DRG
Combination SCS increases spinal perfusion and promotes neutrophil recruitment
Neutrophil signaling contributes to sustained SCS analgesia
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