Role of P2X 7 receptor in microglia in medial prefrontal cortex in neuropathic pain in rats: relationship with autophagy / 中华麻醉学杂志

ABSTRACT

Objective:To evaluate the role of P2X 7 receptor in microglia in the medial prefrontal cortex (mPFC) in neuropathic pain (NP) and the relationship with autophagy in rats. Methods:Sixty-four healthy SPF male Sprague-Dawley rats, aged 6-8 weeks, weighing 200-250 g, were divided into 4 groups ( n=16 each) using a random number table method: sham operation group (S group), NP group, sham operation+ P2X 7 receptor blocking group (SP group), and NP+ P2X 7 receptor blocking group (NP+ P group). The NP model was established by ligation of the sciatic nerve.Fourteen days later a cannula was placed in the mPFC with a brain stereotactic instrument, P2X 7 receptor blocker A-740003 0.5 μg/0.5 μl was injected into bilateral mPFC for 3 consecutive days starting from the 14th day in SP and NP+ P groups, and DMSO 0.5 μl was injected instead of A-740003 in S and NP groups.The mechanical paw withdrawal threshold (MWT) and thermal paw withdrawal latency (TWL) were measured at 3, 7 and 10 days after establishing the model and 14, 15 and 16 days after administration.Then the rats were sacrificed, and the mPFC was removed for determination of the expression of P2X 7 receptor and mRNA and autophagy-related proteins Beclin1 and LC3Ⅱ/Ⅰ (by quantitative real-time polymerase chain reaction or by Western blot) and co-expression of P2X 7R and microglia (by immunofluorescence) and the number of autophagosomes in mPFC (with a transmission electron microscope). Results:Compared with group S, MWT was significantly decreased, and TWL was shortened at 3, 7 and 10 days after establishing the model, the expression of P2X 7 receptor and mRNA, Beclin1 and LC3Ⅱ/Ⅰ was up-regulated at 30 min after administration on 16 days after establishing the model, and the number of cells co-expressing P2X 7 receptor and IBA-1 and the number of autophagosomes were increased in NP and NP+ P groups ( P<0.05), and no significant change was found in the indexes mentioned above in group SP ( P>0.05). Compared with group NP, MWT was significantly increased, and TWL was prolonged at 30 min after administration on 14, 15 and 16 days after establishing the model, the expression of P2X 7 receptor and mRNA, Beclin1 and LC3Ⅱ/Ⅰ was down-regulated, and the number of cells co-expressing P2X 7 receptor and Iba-1 and the number of autophagosome were decreased in group NP+ P ( P<0.05). Conclusion:Up-regulation of P2X 7 receptor expression in microglia in mPFC is involved in the process of NP in rats, which is associated with the promotion of autophagy.