Effect of Electroacupuncture at Hegu (LI 4) on P2X2 and P2X3 Receptors in Trigeminal Ganglion in Pulpalgia Rats / 上海针灸杂志

ABSTRACT

Objective To explore the effect of electroacupuncture at Hegu (LI 4) on the expressions of P2X2 and P2X3 receptors in experimental pulpalgia rats.Method Forty-two male SD rats were randomized into a normal group (group N), a control group (group C), a pulpalgia model group (group M), an antagonist group (group A), an electroacupuncture group (group E), and an antagonist+electroacupuncture group (group AE), 7 rats in each group. Group N didn’t receive any interventions; group C received injection of normal saline into pulp cavity of the same dose as the injection in group M, and the cavity was then blocked by dental fillings 5-6 min later; in group M, maxillary first and second molar teeth were drilled (drill bit of 1 mm in diameter) to expose pulp and lipopolysaccharide (LPS) solution 5μg/μL was injected into the holes (1~3μL for each hole), and the holes were then covered by dental fillings 5-6 min later; group A received the same modeling method as that in group M, but A-317491 was injected together with LPS (0.5 mg/kg); group E received electroacupuncture at bilateral Hegu (LI 4) with needles retained for 30 min, once a day, totally for 3 times; group AE received the same electroacupuncture intervention after receiving the same treatments as that in group A. The rats’ behaviors and weight were observed for 30 min after intervention each day. The rats were sacrificed on the 4th day, and the mRNA expressions of P2X2 and P2X3 receptors andβ-actin in trigeminal ganglion were detected by using RT-PCR. The mRNA expressions were then compared among the groups.Result The behavioral changes in group M, E, and AE were more significant than that in group C and N (P<0.01); the behavioral changes in group A, E, and AE were less significant than that in group M (P<0.01). The weight in group C was significantly lower than that in group N (P<0.01); the weights in group M, A, E and AE were significantly lower than that in group C and N (P<0.01); the weights in group E and AE were significantly higher than that in group M and A (P<0.01,P<0.05); the weight in group A was slightly higher than that in group M (P<0.05); the weights in group AE was significantly higher than that in group E (P<0.01). The mRNA expressions of P2X2 receptor in group M, A, and AE were significantly higher than that in group N and C (P<0.01); the mRNA expressions of P2X2 receptor in group A, E, and AE were lower than that in group M (P<0.05); the mRNA expression of P2X2 receptor in group A was lower than that in group E (P<0.05); the mRNA expression of P2X2 receptor in group E was higher than that in group AE (P<0.05). The mRNA expressions of P2X3 receptor in group M, A, and E were significantly higher than that in group C (P<0.05) and group N (P<0.01); the mRNA expressions of P2X3 receptor in group A, E, and AE were significantly lower than that in group M (P<0.01); the mRNA expression of P2X3 receptor in group AE was markedly lower than that in group E (P<0.01).Conclusion The expressions of P2X2 and P2X3 receptors in trigeminal ganglion were increased in LPS-induced pulpalgia rats. Electroacupuncture at Hegu (LI 4) and injection of A-317491 both can down-regulate the mRNA expressions of P2X2 and P2X3 receptors, which is plausibly the action mechanism of electroacupuncture at Hegu (LI 4) in analgesia.