Abstract:Objective To investigate the regulatory effect of circadian clock genes in reducing blood pressure by acupuncture in spontaneously hypertensive rats (SHRs). Methods A total of 24 SHRs were randomly divided into acupuncture group and model group, and 12 Wistar Kyoto (WKY) rats were selected as normal group. The rats in the acupuncture group were given acupuncture at bilateral Quchi and Zusanli acupoints during the period of the day from 7 a.m. to 9 a.m., and those in the model group and the normal group were tied up with the same intensity as the acupuncture group. Four weeks later, six rats were randomly selected from each group during the periods of the day from 7 a.m. to 9 a.m. and from 5 p.m. to 7 p.m. to measure rat tail systolic blood pressure (SBP) and diastolic blood pressure (DBP), as well as the serum levels of 5-hydroxytryptamine (5-HT) and melatonin (MT) and the mRNA expression of the circadian clock genes Clock and Bmal1. Results The main effects of grouping factors on SBP, DBP, serum MT, and RQ values of the expression of Clock and Bmal1 were statistically significant (P<0.05), while the main effect of time factor on each index and the interaction between them was not statistically significant (P>0.05). Compared with the normal group, the model group had significantly higher SBP and DBP during the periods of the day from 7 a.m. to 9 a.m. and from 5 p.m. to 7 p.m. (P<0.05), and compared with the model group, the acupuncture group had significantly lower SBP and DBP during the period of the day from 7 a.m. to 9 a.m. and a significantly lower SBP during the period of the day from 5 p.m. to 7 p.m. (P<0.05). Compared with the normal group, the model group had a significant reduction in MT and a significant increase in 5-HT during the period of the day from 7 a.m. to 9 a.m. (P<0.05); compared with the model group, the acupuncture group had a significant increase in MT and a significant reduction in 5-HT during the period of the day from 7 a.m. to 9 a.m. (P<0.05), as well as a significant increase in MT during the period of the day from 5 p.m. to 7 p.m. (P<0.05). Compared with the model group, the acupuncture group had a significant increase in the mRNA expression of Clock during the period of the day from 7 a.m. to 9 a.m. and a significant increase in the mRNA expression of Bmal1 during the period of the day from 5 p.m. to 7 p.m. (P<0.05). Conclusion Acupuncture during the period of the day from 7 a.m. to 9 a.m. can reduce "bimodal" blood pressure of SHR, possibly by increasing serum MT, reducing 5-HT, and increasing the mRNA expression of the Clock and Bmal1 genes in the heart.