Abstract: Objective To investigate the role of glucocorticoids(GCs) in anxiety-induced mechanical hyperalgesia in rats. Methods Seventy-two rats were divided into two part of experiments. ① Behavioral test. 24 rats were randomly divided into 3 groups(n=8): control group(C group), single prolonged stress(SPS) group(A group), SPS+metyrapone group(M group). A group and M group were exposed to SPS. Intraperitoneal injection of metyrapone(25 mg/kg) was performed 1 h before SPS procedure. Elevated plus-maze test was tested on the first day after the SPS exposure. Paw withdrawal mechanical threshold (PWMT) was test on day 1 before SPS(T0) and days 1(T1), 4(T2), 7(T3), 14(T4) after SPS. ② Western blot. 48 rats were used, glucocorticoid receptor(GR) protein expression of A group was tested by Western blot in T0, T1, T3, T4, 3 rats in each time point. GR protein expression of every group was tested by Western blot in T1, T2, T3, T4, 3 rats in each group. Results In the elevated plus?蛳maze test, the number of entries and the percentage of time spent in open?蛳arms of A group[(4.6±1.5), (12.0±1.9)%] was significantly decreased compared with C group[(12.3±1.8), (17.8±2.5)%] and M group[(9.9±1.5), (16.4±3.3)%](P<0.05). The PWMT of A group was significantly decreased on 1, 4, 7, 14 d after SPS compared with C group(P<0.05), the PWMT of M group was significantly increased on 1, 4, 7, 14 d compared with A group(P<0.05). The expression levels of glucocorticoid receptor(GR) in the spinal cord were increased significantly after SPS exposure, and it lasted 14 days(P<0.05). The expression levels of GR of M group were significantly increased compared with A group(P<0.05). Conclusions GCs are involved in anxiety-induced hyperalgesia in rats exposed to SPS. Metyrapone can significantly inhibit anxiety-induced mechanical hyperalgesia.
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