〔Abstract〕 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 hypo- tension , 35 cases (40. 2% ) ; Anesthesia-1 group , pregnant women had hypotension and good response to ephed- rine 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 CGRPαin serum and placental tissues of pregnant women were deter- mined by ELISA . The rats pregnant normally. A hypotension rat model was established by intragastric administra- tion of risserpine . 50 rats were randomly divided into control group , model group , pregnancy group , model + preg- nancy 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 meas- ured at the end of the 6th induction week . And the peripheral blood sample and placental tissues were collected and the levels of CGRPαwere determined . Results The detection of CGRPαlevels in the pregnant women serum and placental tissues showed that compared with Anesthesia-0 group , CGRPαlevels in Anesthesia-1-4 groups serum were higher (P < 0. 05 ) . Compared with Anesthesia-3 group , serum CGRPαlevels in Anesthesia-4 group were higher (P < 0. 05) . Compared with Anesthesia-2 group , CGRPαlevels in Anesthesia-4 group serum were higher (P < 0. 05) . Compared with Anesthesia-0 group , tissues CGRPαlevels in Anesthesia-4 group were higher (P < 0. 05) . Compared with Anesthesia-3 group , CGRPαlevels in Anesthesia-4 group tissues were higher (P < 0. 05) . Compared with Anesthesia-2 group , CGRPαlevels in Anesthesia-4 group tissues were higher ( P < 0. 05 ) . From the 2nd to 6th week of hypotension modeling induction , compared with pregnancy group , body weight decreased in the model + pregnancy group and the model + pregnancy + phenylephrine group (P < 0. 05) . There was no signifi- cant difference in baseline systolic blood pressure among all groups (P > 0. 05) . At the end of the 6th week , com- pared with pregnancy group , systolic blood pressure decreased in model + pregnancy group and model + pregnancy + phenylephrine group(P < 0. 05) ; the levels of CGRPαin serum and placental tissues increased ( P < 0. 05) . Compared with model + pregnancy group , systolic blood pressure increased in model + pregnancy + phenylephrine group (P < 0. 05) . Conclusion The poor response of pregnant women with hypotension during caesarean section under intraspinal anesthesia to the treatment of phenylephrine may be related to the increased levels of CGRPαin placenta and peripheral blood .