Application of HFES significantly attenuates capsaicin-induced increases in HMGB1 (HMGB1: control = 11.9 ± 2.4 ng/mL, capsaicin = 55.3 ± 7.9 ng/mL, capsaicin + HF stimulation = 28.2 ± 7.4 ng/mL, *P < 0.05, Fig. 2A), CGRP (CGRP: control = 47.2 ± 4.0 pg/mL, capsaicin = 118.6 ± 5.1 pg/mL, capsaicin + HF stimulation = 79.1 ± 9.3 pg/mL, **P < 0.01, Fig. 2B) and substance P (Substance P: control = 5.3 ± 1.2 pg/mL, capsaicin = 36.7 ± 3.5 pg/mL, capsaicin + HF stimulation = 18.0 ± 2.7 pg/mL, ****P < 0.0001, Fig. 2C). This evidence concerns the gene HMGB1 and hydrops fetalis.