Objective:To evaluate the role of P2X4 receptor (P2X4R) in the maintenance of trigeminal neuralgia and the relationship with p38 mitogen-activated protein kinase (p38 MAPK)/brain-derived neurotrophic factor (BDNF) signaling pathway in rats.Methods:Forty-eight clean-grade healthy adult male Sprague-Dawley rats, weighing 190-230 g, aged 2-3 months, were divided into 4 groups ( n=12 each) using a random number table method: sham operation group (S group), trigeminal neuralgia group (TN group), trigeminal neuralgia+ dimethylsulfoxide (DMSO) group (TN+ DMSO group), and trigeminal neuralgia+ P2X4R specific antagonist 5-BDBD group (TN+ 5-BDBD group). The model was developed by chronic constriction of the infraorbital nerve. The infraorbital nerve was only exposed without ligation in group S. At 3, 7, 10 and 14 days after developing the model, 5 μg/μl 5-BDBD 10 μl was intrathecally injected in TN+ 5-BDBD group, and 2% DMSO 10 μl was intrathecally injected in TN+ DMSO group. The facial mechanical pain withdrawal threshold (MWT) was measured at 1 day before developing the model and 1, 3, 7, 10, 14 and 28 days after developing the model (T 0-6). The rats were sacrificed and the trigeminal ganglia were taken for determination of the expression of P2X4R, p38 MAPK, phosphorylated p38 MAPK (p-p38 MAPK) and BDNF (by Western blot) and contents of tumor necrosis factor (TNF)-α and interleukin (IL)-1β and IL-6 (by enzyme-linked immunosorbent assay). Results:Compared with group S, the MWT was significantly decreased at T 1-6, the expression of P2X4R, p-p38 MAPK and BDNF in trigeminal ganglion was up-regulated, and the contents of TNF-α, IL-1β and IL-6 were increased in TN group ( P<0.05). Compared with TN group, the MWT was significantly increased at T 3-6, and the expression of P2X4R, p-p38 MAPK and BDNF in trigeminal ganglion was down-regulated, and the contents of TNF-α, IL-1β and IL-6 were decreased in TN+ 5-BDBD group ( P<0.05), and no significant change was found in the indexes mentioned above in TN+ DMSO group ( P>0.05). Conclusions:P2X4R is involved in the maintenance of trigeminal neuralgia in rats, which may be related to the activation of p38 MAPK/BDNF signaling pathway and the increase in inflammatory mediator release.