〔Abstract〕 Objective To investigate the correlation between the levels of calcitonin gene-related peptide α(CGRPα) and the poor responses to the treatment of phenylephrine in pregnant women with hypotension during caesarean section under intraspinal anesthesia.Methods A total of 87 pregnant women who underwent intraspinal anesthesia cesarean section were recruited.They were grouped according to the presence or absence of hypotension after anesthesia and the response to ephedrine and Phe.As to Anesthesia-0 group,pregnant women had no hypotension,35 cases(40.2%);Anesthesia-1 group,pregnant women had hypotension and good response to ephedrine treatment,12 cases(13.8%);Anesthesia-2 group,pregnant women had hypotension and had poor response to ephedrine treatment,6 cases(6.9%);Anesthesia-3 group,pregnant women had hypotension and good response to Phe treatment,8 cases(9.2%);Anesthesia-4 group,pregnant women had hypotension and no response to Phe treatment,26 cases(29.9%).The levels of CGRPα in serum and placental tissues of pregnant women were determined by ELISA.The rats pregnant normally.A hypotension rat model was established by intragastric administration of risserpine.50 rats were randomly divided into control group,model group,pregnancy group,model+pregnancy group,model+pregnancy+phenylephrine group,with 10 rats in each group.Body weight of the rats was continuously monitored during the 2nd to 6th week of risserpine administration.Systolic blood pressure was measured at the end of the 6th induction week.And the peripheral blood sample and placental tissues were collected and the levels of CGRPα were determined.Results The detection of CGRPα levels in the pregnant women serum and placental tissues showed that compared with Anesthesia-0 group,CGRPα levels in Anesthesia-1-4 groups serum were higher(P 0.05).At the end of the 6th week,compared with pregnancy group,systolic blood pressure decreased in model+pregnancy group and model+pregnancy+phenylephrine group(P