Influence of acupuncture twisting parameters on analgesic effects mediated by mast cells in AA rat models

Acupuncture has been recognized for its potential effectiveness in pain relief without the side effects commonly associated with pharmaceutical treatments. This study investigates the effects of various acupuncture twisting parameters on analgesia using an acute adjuvant-induced arthritis (AA) rat model, focusing on the roles of mast cell activation, histamine (HIS) release, and local neural pathways. Utilizing robot-assisted acupuncture, we varied rotation angles (60°-360°) and frequencies (0.5-2.5 Hz) to evaluate their influence on pain modulation. The pain threshold recovery ratio (PTRR) was used to quantify the analgesic effect. The optimal combination of a 180° rotation angle and 1.0 Hz frequency resulted in the strongest analgesic effect, as indicated by increased PTRR and elevated mast cell degranulation rates (MCdR). Additionally, local HIS injections replicated the analgesic effects of acupuncture, whereas administration of an H1 receptor antagonist and lidocaine reduced these effects, highlighting the essential roles of HIS and local nerve conduction in acupuncture-induced analgesia. This study demonstrates the existence of optimal acupuncture parameters for achieving maximal analgesic effects in rat models, and elucidates the critical role of mast cell-mediated neural pathways, thus providing insights into optimizing acupunctire's clinical application in pain management.