Phloroglucinol inhibits oxytocin-induced contraction in rat gastric circular muscle and uterine smooth muscle

Phloroglucinol is commonly used to alleviate dysmenorrhoea and stomach cramps. However, there is little evidence of phloroglucinol in the mechanism of primary dysmenorrhoea (PD) development. In this study, a PD rat model was established. The effects of phloroglucinol on the contraction of rat gastric circular muscle and uterine smooth muscle induced by oxytocin (OT) were investigated. The writhing response, and levels of oestradiol (E2), prostaglandin e2 (PGE2), and prostaglandin f2α (PGF2α) were determined. The protein and mRNA levels of OT receptor (OTR) were detected. OT showed a significant promoting effect on gastric circular muscle and uterine smooth muscle contraction. However, phloroglucinol strongly inhibited the contraction induced by 10 −6 mol/L of OT. We also found that phloroglucinol reduced writhing response and attenuated uterine damage. Compared to the blank group, E2 and PGF2α were significantly increased, but PGE2 was significantly decreased in the PD model group. Phloroglucinol was found to reverse the changes of E2, PGF2α and PGE2. Moreover, phloroglucinol reduced the protein and mRNA levels of OTR. In conclusion, phloroglucinol could attenuate PD and inhibit the contraction of rat gastric circular muscle and uterine smooth muscle induced by OT. The mechanism might be related with the regulation of OTR expression. IMPACT STATEMENT What is already known on this subject? Phloroglucinol is commonly used to alleviate dysmenorrhoea and stomach cramps. However, there is little evidence of phloroglucinol in the mechanism of primary dysmenorrhoea (PD) development. What do the results of this study add? Phloroglucinol could attenuate PD and inhibit the contraction of rat gastric circular muscle and uterine smooth muscle induced by OT. The underlying mechanisms of phloroglucinol for PD treatment may be associated with OTR. What are the implications of these findings for clinical practice and/or further research? These findings provide novel ideas for the role of phloroglucinol in PD development.