Effects and Mechanisms of Wrist-Ankle Acupuncture on Inflammatory Pain in the Rat Gastrocnemius Muscle

To compare the therapeutic effects of wrist-ankle acupuncture stimulation (WAA-AS) and wrist-ankle acupuncture theory-based transcutaneous electrical nerve stimulation (WAA-TENS), and explore the mechanism of wrist-ankle acupuncture (WAA) using transcriptomic analysis.

Sprague-Dawley rats were randomly divided into control (CON), model (MOD), WAA-TENS and WAA-AS groups. An inflammatory pain model was established by complete Freund's adjuvant (CFA) injection into the gastrocnemius muscle. Mechanical pain thresholds, inflammatory infiltration and collagen deposition were evaluated. Inflammatory factors were measured by ELISA. Transcriptomic sequencing, PPI network analysis and RT-qPCR were performed.

Compared with the model group, both WAA-TENS and WAA-AS significantly increased pain thresholds: post-intervention pain thresholds increased to ~7 g (WAA-AS) and ~7-8 g (WAA-TENS), a 2.2-3-fold elevation vs the persistently low ~2-3 g in the MOD group (p < 0.01), reduced inflammatory infiltration and collagen deposition, downregulated IL-1β, IL-6 and TNF-α, and upregulated TGF-β. Core circadian rhythm-related genes (Cd74, Cry1, Per2, Nfil3, Nr1d2, Npas2) were screened. RT-qPCR verified that WAA-TENS upregulated Per2 and Nr1d2 and downregulated Nfil3, while WAA-AS decreased Cry1 and Nfil3.

WAA-TENS and WAA-AS exert comparable analgesic and anti-inflammatory effects and inhibit excessive collagen synthesis. WAA-TENS may represent a promising alternative to WAA-AS for acute-phase intervention, based on our preliminary findings. The mechanism may involve regulating circadian rhythm-related genes including Cry1, Per2, Nfil3 and Nr1d2.