[Effect of Xingnao Kaiqiao acupuncture therapy on ischemic stroke in rats based on Zn²⁺-mediated TRPA1 channel]

To observe the effect of Xingnao Kaiqiao (regaining consciousness and opening orifices) acupuncture therapy on the local vasodilatation of ischemic stroke rats, so as to elucidate the mechanism of the protective effect of acupuncture on ischemic brain injury.

Eighty SPF-grade male SD rats were randomly divided into a sham-operation group, a model group, an acupuncture group and a zinc chelator (TPEN) group, with 20 rats in each group. Except in the sham-operation group, modified Longa filament method was used to establish rat models of middle cerebral artery occlusion in the other groups. In the sham-operation group, the blunt dissection was performed, without the suture occluded. In the acupuncture group, Xingnao Kaiqiao acupuncture therapy was operated at bilateral "Neiguan" (PC6) and "Shuigou" (GV26), and the needles were retained for 30 min, once daily, for consecutively 7 days. In the TPEN group, TPEN was injected intraperitoneally (15 mg/kg), 30 min before modeling. The neurobehavioral scores were assessed 2 h and 7 d after modeling respectively. Before modeling, and 2 h and 7 d after modeling, the diameter of blood vessels in the ischemic area of the right cerebral cortex of rats was measured by laser speckle, and the vascular expansion and contraction ratio was calculated. Seven days after modeling, using 2,3,5-triphenyltetrazolium chloride (TTC) staining method, the percentage of cerebral infarction volume was determined in the ischemic area of the right cerebral cortex of rats, FLOUZin-3 fluorescent probe was used to detect the level of Zn²⁺, Western blotting and real-time quantitative PCR were adopted to detect the protein and mRNA expression of the vasodilation-related transient receptor potential factor 1 (TRPA1) and calcitonin gene-related peptide (CGRP), and calcium test kit was used to detect the content of calcium ion (Ca²⁺) in the ischemic area of the right cerebral cortex of rats.

Seven days after modeling, compared with the sham-operation group, the neurobehavioral score, the percentage of cerebral infarction volume, the level of Zn²⁺ and the contents of Ca²⁺ increased (P<0.05), vascular expansion and contraction ratio was not different statistically (P>0.05), and the mRNA and protein expression of TRPA1 and CGRP decreased (P<0.05) in the model group. Compared with the model group, the neurobehavioral scores, the percentage of cerebral infarction volume, Zn²⁺ levels and Ca²⁺ contents were reduced (P<0.05), vascular expansion and contraction ratio rose (P<0.05), and the mRNA and protein expression of TRPA1 and CGRP was elevated (P<0.05) in the acupuncture group and the TPEN group. When compared with the TPEN group, the neurobehavioral score and the percentage of cerebral infarction volume were elevated (P<0.05), and the differences were not significant statistically in Zn²⁺ level and Ca²⁺ content, vascular expansion and contraction ratio, and the mRNA and protein expression of TRPA1 and CGRP in the acupuncture group (P>0.05).

Xingnao Kaiqiao acupuncture therapy can effectively dilate cerebral blood vessels to alleviate ischemic brain injury, which may be related to reducing the level of free Zn²⁺, activating TRPA1 channel to promote Ca²⁺ influx, thereby releasing CGRP to induce cerebral vasodilation.