Danggui Buxue Decoction and Its Active Constituents Inhibit Drug-Induced Uterine Contractions via L-Type Calcium Channels and the IP3/Ca2+ Pathway

<b>Background/Objectives</b>: Primary dysmenorrhea is a common gynecological disorder characterized by painful uterine contractions. Danggui Buxue Decoction (DBD) is used to treat menstrual irregularities, but its mechanism in primary dysmenorrhea remains unclear. This study investigated the efficacy of DBD against dysmenorrhea and its calcium signaling-related mechanism. <b>Methods</b>: DBD components were analyzed by UPLC-Orbitrap MS. Isolated uterine muscle strips precontracted with oxytocin (OT, 50 ng/mL) or KCl (60 mM) were used to assess the effects of DBD and its active compounds (Quercetin, Formononetin, Ononin, Ferulic acid, Senkyunolide I, Calycosin, Ligustilide, Calycosin-7-O-β-D-glucoside). Ca²⁺-dependent experiments, intracellular calcium release assays, and inhibitor treatments (Nifedipine, 2-APB) were performed to evaluate the involvement of L-type calcium channels and the IP₃R pathway. A primary dysmenorrhea model induced by estradiol benzoate and oxytocin was used to assess the analgesic effects, histopathology, inflammatory factors, and IP₃/Ca²⁺-related proteins and genes following DBD and Quercetin treatment. <b>Results</b>: A total of 161 compounds were identified in DBD. DBD and its eight active constituents relaxed OT (50 ng/mL) or KCl (60 mM)-induced uterine contractions, with Quercetin, Calycosin, and Ligustilide showing particularly prominent relaxant activity. These three compounds suppressed extracellular calcium influx and intracellular calcium release through the blockade of L-type calcium channels and IP₃R. In vivo, DBD and Quercetin alleviated pain, reduced inflammation, and decreased uterine Ca²⁺ and IP₃ levels in dysmenorrhea mice. <b>Conclusions</b>: DBD and its active component Quercetin promote uterine relaxation by lowering Ca²⁺ levels, which is achieved through suppression of L-type calcium channels and the IP₃/Ca²⁺ pathway. This contributes to their therapeutic action against primary dysmenorrhea.