[Electroacupuncture of specific acupoints of Shaoyang Meridian relieves progression of chronic migrain by down-regulating expression of P2Y12 receptor in rats].

Objectives: To observe the effect of electroacupuncture (EA) at specific points of the Shaoyang Meridian on mechanical pain threshold, and expressions of P2Y12 receptor (P2RY12), ionic calcium binding molecule 1 (Iba-1), calcitonin gene-related peptide (CGRP) and c-fos in rats with chronic migraine (CM) , so as to explore its mechanisms underlying prevention and treatment of CM.

Methods: Forty-eight SD rats (half male and half female) were randomly divided into 6 groups (using a random number table method):control, model, EA, antagonist, EA+agonist, and medication groups, with 8 rats in each group. The CM model was established by repeated intraperitoneal injection of nitroglycerin (10 mg/kg, once every other day, 5 times altogether). EA (10 Hz/50 Hz, a strength being able to induce local slight regular muscular contraction of the fore-limb) was applied to bilateral "Fengchi"(GB20), "Yanglingquan"(GB34), and "Waiguan"(TE5) for 30 min, once a day before modeling and once every other day during modeling, for a total of 6 times. The rats of the antagonist group received intrathecal injection of P2RY12 antagonist MRS2395 (200 μg/rat) , once every other day for a total of 5 times. Rats of the EA+agonist group received intrathecal injection of P2RY12 agonist ADP (4.272 μg/rat) once every other day for a total of 5 times, and those of the medication group received intraperitoneal injection of topiramate (30 mg/kg) once a day for 9 d. Rats of the other groups were bound for 30 min during EA. On the 1^st, 3^rd, 5^th, 7^th, and 9^th day of modeling, 2 h before the intervention, the mechanical pain thresholds of the periorbital region of the eye and the plantar region of the hindlimb in each group were measured using a von Frey filament. The number of P2RY12 positive cells and the expression of P2RY12 mRNA in the caudal nucleus of the trigeminal spinal tract (TNC) were detected using immunofluorescence staining and real-time fluorescence quantitative PCR, separately, and the expression levels of P2RY12, Iba-1, CGRP, and c-fos proteins in the TNC tissue were detected using Western blot.

Results: In comparison with the control group, the periorbital and plantar pain thresholds were significantly reduced (P<0.001), while the expression levels of P2RY12, Iba-1, CGRP, and c-fos proteins in the TNC tissue, and the number of P2RY12 positive cells and P2RY12 mRNA expression were significantly increased in the model group (P<0.001). Compared with the model group, the periorbital and plantar pain thresholds of the EA, antagonist and medication groups were significantly increased (P<0.001), while the expression levels of P2RY12, Iba-1, CGRP, and c-fos proteins, number of P2RY12 positive neurons, and P2RY12 mRNA expression were apparently decreased in the EA, antagonist, medication and EA+agonist groups (P<0.001, P<0.05). The effect of EA was strikingly superior to that of EA+agonist in increasing periorbital and plantar pain thresholds (P<0.001, P<0.05), lowering the expressions of P2RY12, Iba-1, CGRP and c-fos, the number of P2RY12 positive cells, and P2RY12 mRNA expression (P<0.05, P<0.001), and superior to that of medication in lowering the number of P2RY12 positive cells and P2RY12 mRNA expression (P<0.05, P<0.01).

Conclusions: EA of the specific points of Shaoyang Meridian can prevent the progression of migraine, and reduce pain, which may be related to its function in down-regulating the expressions of P2RY12 protein and mRNA, Iba-1, and CGRP and c-fos proteins (central sensitization-related indexes) in TNC.