Intrathecal Injection of Ropivacaine Reduces Cervical Resistance in Late-Pregnant Rats

PURPOSE: Neuraxial (spinal and epidural) anesthesia is the cornerstone of ensuring the satisfaction rate of painless delivery; however, whether it prolongs the first stage of labor remains controversial. Although current clinical research results tend to be negative, the conclusions are not convincing due to the lack of basic research. This study was conducted to provide a theoretical reference for this controversy through basic research. MATERIALS AND METHODS: A spinal anesthesia model was established by the intrathecal injection of 0.1% ropivacaine in late-pregnant rats (day 22). The cervical resistance test was used to measure the tension of different groups of isolated cervical tissues. Western blotting and cervical tissue cyclic AMP (cAMP) enzyme-linked immunosorbent assay were performed to clarify the possible related mechanisms. RESULTS: Cervical resistance experiments showed that the intrathecal injection of ropivacaine decreased the cervical resistance, and norepinephrine injection reversed this effect. Western blotting showed that α2A adrenergic receptor (α(2A)-AR) levels gradually increased over time in pregnant rats. The cAMP enzyme-linked immunosorbent assay revealed that the intrathecal injection of norepinephrine reversed the increase in cervical tissue cAMP concentration caused by ropivacaine injection. CONCLUSION: Ropivacaine relaxes the cervix. Further, α(2)-AR may be involved in the process of cervical contraction.