[Influence of electroacupuncture of"Zusanli"(ST36)on mast cells/TRPV1 signaling pathway in visceral hypersensitivity rats with functional dyspepsia].

Abstract

To explore the interventional mechanism of electroacupuncture (EA) of "Zusanli"(ST36)based on the involvement of mast cells/ transient receptor potential vanilloid type1 (TRPV1) signaling pathway in relieving visceral hypersensitivity in functional dyspepsia (FD) rats. Sixty SD rats (half male and half female, 10 days in age) were randomly divided into normal control, model, medication (ketotifen) and EA groups, with 15 rats in each group. The FD model was established by gavage of iodoacetamide combined with tail clamping (stress stimulation). Rats of the medication group received intraperitoneal injection of ketotifen (1 mg·kg-1·d-1) for 14 d, and those of the EA group received EA of ST36 for 20 min, once a day for 14 d. An air-balloon was inserted into the rat's stomach for recording changes of the intragastric pressure (mL/mm Hg) via a pressure transducer. The visceral hypersensitivity was assessed using abdominal withdrawal reflex (AWR) score and the number and degranulation of mast cells of gastric mucosa were observed using toluidine blue staining. The expression levels of TRPV1 and proteinase activated receptor 2 (PAR2) in the stomach were observed using immunofluorescence histochemistry and Western blot, separately, and the contents of SP and CGRP in the stomach detected using ELISA. When the intragastric pressure was at 50, 60 and 70 mm Hg, the gastric compliance was significantly decreased (P<0.01), and the levels of visceral sensitivity increased in the model group （P<0.01）。 TRPV1 immunofluorescence tensity, expression of PAR2 and TRPV1 proteins, and contents of SP and CGRP in the stomach were considerably up-regulated in the model group compared with the normal control group (P<0.01). In comparison with the model group, under intragastric pressure of 50，60 and 70 mm Hg, the gastric compliance was obviously increased, and the visceral hypersensitivity decreased in the EA group （P<0.01,P<0.05）. TRPV1 immunofluorescence intensity, expression levels of PAR2 and TRPV1 proteins, and the contents of SP and CGRP in the stomach were considerably down-regulated in both medication and EA groups compared with the model group (P<0.01, P<0.05). The therapeutic effect of EA was significantly superior to that of medication in up-regulating the gastric compliance （at 70 mm Hg）, and down-regulating the contents of SP and CGRP (P<0.05). No significant differences were found between the EA and medication groups in up-regulating gastric compliance at intragastric pressure of 50 and 60 mm Hg, and in down-regulating the visceral sensitivity, TRPV1 fluorescence intensity, and expression of PAR2 and TRPV1 proteins (P>0.05). Toluidine blue staining showed an apparent increase of mast cell number with obvious degranulation in the gastric mucosa of rats in the model group, which was milder in the EA and medication groups. EA of ST36 can suppress visceral hypersensitivity and increase the gastric compliance in FD rats, which may be related with its effects in inhibiting the activation of gastric mast cells, and down-regulating the expression of gastric PAR2 and TRPV1 proteins and SP and CGRP contents.