[Study on the antihypertensive mechanism of acupuncture at "Renying" (ST9) and "Zusanli" (ST36) via gastrin/cholecystokinin B receptors].

Objectives: To observe the effect of acupuncture on serum gastrin content and urinary sodium excretion in spontaneously hypertensive rat (SHR), so as to explore its potential mechanism in the treatment of hypertension.
Methods: Thirty-two male SHRs were randomly divided into model, hydrochlorothiazide, acupuncture and sham acupuncture groups, with 8 rats in each group, and 8 male Wistar-kyoto rats were taken as the control group. Rats in the hydrochlorothiazide group received gavage of hydrochlorothiazide solution (10 mg·kg ^-1 ·d ^-1 ), once daily for 4 weeks. Acupuncture was applied to bilateral "Renying" (ST9) and "Zusanli" (ST36) or non-acupoint on both sides for rats in the acupuncture and sham acupuncture groups, with manual stimulation every 10 minutes for a total of 20 minutes, once a day for a total of 4 weeks. The systolic blood pressure of the tail-artery was measured before and 1, 2, 3, and 4 weeks after the intervention. HE staining was used to observe the pathological changes in renal tissue. Serum gastrin contents were detected using enzyme-linked immunosorbent assay (ELISA). Urinary sodium content was measured by atomic absorption spectrometry. The expression levels of cholecystokinin B receptor (CCKBR) and Na ⁺ /K ⁺ -ATPase proteins in renal tissue were detected by Western blot, and the mRNA expression levels of CCKBR and the α1 subunit of Na ⁺ /K ⁺ - ATPase (ATP1A1) were detected by fluorescence quantitative PCR.
Results: Compared with the control group, the systolic blood pressure of the tail artery in the model group were increased significantly before intervention and at the 1 ^st , 2 ^nd , 3 ^rd and 4 ^th weeks of intervention ( P <0.05). Before intervention, the 24 h urine volume of the model, hydrochlorothiazide, acupuncture and sham acupuncture groups were decreased significantly ( P <0.05). After intervention, the 24 h urine volume and urinary sodium excretion in the model group were significantly decreased ( P <0.05)；the expression levels of CCKBR protein and mRNA in renal tissue were significantly decreased ( P <0.05)；the expression levels of Na ⁺ /K ⁺ -ATPase protein and ATP1A1 mRNA were significantly increased ( P <0.05)；the glomerulus was mildly congested with a small amount of lymphocyte infiltration. Compared with the model group, the systolic blood pressure of the tail artery in the hydrochlorothiazide and the acupuncture groups were decreased significantly at the 2 ^nd , 3 ^rd and 4 ^th weeks of intervention ( P <0.05)；the 24 h urine volume and urinary sodium excretion in the hydrochlorothiazide and the acupuncture groups were significantly increased ( P <0.05)；the serum gastrin content and the expression levels of CCKBR protein and mRNA in renal tissue were significantly increased ( P <0.05)；the expression levels of Na ⁺ /K ⁺ -ATPase protein and ATP1A1 mRNA were significantly decreased ( P <0.05)；there were no obvious pathological changes in renal tissue. A small number of lymphocyte focal infiltration around blood vessels was observed in the kidney tissue of the sham acupuncture group.
Conclusions: Acupuncture can significantly reduce the tail artery systolic blood pressure of SHR, which may be related to its effect in increasing serum gastrin content and CCKBR expression, inhibiting sodium pump reabsorption, thus promoting urinary sodium excretion.