Aim:To investigate whether the circadian expression of central clock genes andangiotensin Ⅱ type 1 (AT1) receptors was altered in sinoaortic-denervated (SAD)rats.Methods:Male Sprague-Dawley rats underwent sinoaortic denervation or asham operation at the age of 12 weeks.Four weeks after the operation,bloodpressure and heart period were measured in the conscious state in a group ofsham-operated (n=10) and SAD rats (n=9).Rest SAD and sham-operated ratswere divided into 6 groups (n=6 in each group).The suprachiasmatic nuclei (SCN)tissues were taken every 4 h throughout the day from each group for the determi-nation of the mRNA expression of clock genes (Per2 and Bmal1) and the AT1receptor by RT-PCR;the protein expression of Per2 and Bmal1 was determined byWestern blotting.Results:Blood pressure levels in the SAD rats were similar tothose of the sham-operated rats.However,blood pressure variabilities signifi-cantly increased in the SAD rats compared with the sham-operated rats.Thecircadian variation of clock genes in the SCN of the sham-operated rats was char-acterized by a marked increase in the mRNA and protein expression during darkperiods.Per2 and Bmal1 mRNA levels were significantly lower in the SAD rats,especially during dark periods.Western blot analysis confirmed an attenuation ofthe circadian rhythm of the 2 clock proteins in the SCN of the SAD rats.AT1receptor mRNA expressions in the SCN were abnormally upregulated in the lightphase,changed to a 12-h cycle in the SAD rats.Conclusion:The circadian varia-tion of the 2 central clock genes was attenuated in the SAD rats.Arterial baroreflexdysfunction also induced a disturbance in the expression of AT1 receptors in theSCN. A check that the circadian expression of central clock genes and angiotensin II type 1 (AT1) receptors was altered in sinoaortic-denervated (SAD) rats. Methods: Male Sprague-Dawley rats underwent sinoaortic denervation or asham operation at the age of 12 weeks .Four weeks after the operation, blood pressure and heart period were measured in the conscious state in a group of patients-operated (n = 10) and SAD rats (n = 9) .Rest SAD and sham-operated ratswere divided into 6 groups (n = 6 in each group. The suprachiasmatic nuclei (SCN) tissues were taken every 4 h throughout the day from each group for the determi-nation of the mRNA expression of clock genes (Per2 and Bmal1) and the AT1 receptor by RT-PCR; The protein expression of Per2 and Bmal1 was determined by Western blotting. Results: Blood pressure levels in the SAD rats were similar to Tothose of the sham-operated rats. Host, blood pressure variabilities signifi-cantly increased in the SAD rats compared with the sham-operated rats.Thecircadia n variation of clock genes in the SCN of the sham-operated rats was char-acterized by a marked increase in the mRNA and protein expression during dark periods. Per2 and Bmal1 mRNA levels were significantly lower in the SAD rats, especially during dark periods. Western blot analysis confirmed an attenuation of the circadian rhythm of the 2 clock proteins in the SCN of the SAD rats. AT1 receptor mRNA expression in the SCN were abnormally upregulated in the light phase, changed to a 12-h cycle in the SAD rats. Confluence: The circadian varia-tion of the 2 central clock genes was attenuated in the SAD rats. Arterial baroreflexdysfunction also induced a disturbance in the expression of AT1 receptors in theSCN.