[Effect of Different Stimulating Strength of Electroacupuncture on Gastrointestinal Motility and RhoA/ROCK Signaling in Gastric Antral Smooth Muscle in Diabetic Gastroparesis Rats].

OBJECTIVE: To observe the effect of different strength of electroacupuncture (EA) stimulation on gastrointestinal motility and Ras homolog gene family member (RhoA)/Rho associated coiled-coil forming protein kinase (ROCK) signaling in diabetic gastroparesis (DGP) rats, so as to reveal the underlying mechanisms of EA for improving DGP.

METHODS: Sixty SD rats were randomly and equally divided into blank control, DGP model, weak EA, medium EA, and strong EA groups ( n ＝12 rats in each). The DGP model was established by intraperitoneal injection of streptozotocin (STZ, 55 mmol/kg, 2%) and high-sugar and high-fat fodder feeding for 8 weeks. EA (0.12, 0.24, 0.36 mA, 20 Hz/100 Hz) was applied to "Zusanli" (ST 36), "Sanyinjiao" (SP 6) and "Liangmen" (ST 21) for 20 min, once daily for 15 successive days. Blood glucose levels were measured weekly with blood glucose meter and blood glucose test paper. Fecal phenol red excretion method was used to display gastric emptying and small intestinal propulsion function. The expression of RhoA protein in the gastric antral smooth muscle tissue was detected by immunohistochemistry and Western blot (WB), separately, and that of ROCK, myosin phosphatase target subunit 1 (MYPT 1) and phosphorylated (p)-MYPT 1 proteins in gastric antrum detected by WB.

RESULTS: Compared with the blank control group, the gastric emptying rate and small intestine propulsion rate of the model group were significantly decreased ( P <0.05), and the blood glucose level was remarkably increased ( P <0.05). Moreover, the expression levels of RhoA, ROCK, MYPT 1 and p-MYPT 1 proteins in the gastric antrum were significantly down-regulated relevant to the control group ( P <0.05). After administration of EA, the decreased gastric emptying rate and intestinal propulsion rate, and the down-regulated expression of RhoA, ROCK, MYPT 1 and p-MYPT 1 proteins were significantly increased in the strong, medium and weak EA stimulation groups ( P <0.05). Comparison among the 3 EA groups showed that the strong stimulation was significantly superior to weak stimulation in up-regulating the expression of RhoA, ROCK, MYPT 1 and p-MYPT 1 proteins, and obviously superior to the medium stimulation in up-regulating RhoA and MYPT 1 protein levels ( P <0.05), while the medium stimulation was significantly stronger than the weak stimulation in up-regulating the expression of ROCK, MYPT 1 and p-MYPT 1 proteins ( P <0.05). There were no significant differences among the 3 EA groups in up-regulating the gastric emptying rate and small intestinal propulsion rate, and between the strong stimulation and medium stimulation in the expression levels of ROCK and p-MYPT 1 proteins ( P >0.05).

CONCLUSION: Electroacupuncture stimulation of ST 36-SP 6-ST 21 at 0.12, 0.24 and 0.36 mA can promote the gastrointestinal motility in DGP rats, which may be associated with its effects in enhancing RhoA/ROCK signaling in the gastric antral smooth muscle at different degrees.