Figure 3. Glucocorticoids decrease the threshold of mechanical allodynia in PSL mice via P2Y12 receptor in the ipsilateral spinal cord.
(a) Diurnal oscillations in ATP release from spinal slices were abrogated by adrenalectomy (means±s.e.m.; n=5–6). Significant time-dependent variations are observed in ATP release from the ipsilateral (Ipsi.) (F5,30=2.552, P=0.035; ANOVA) and contralateral (Contra.) sides (F5,30=2.049, P=0.048; ANOVA). (b) Subcutaneous (s.c.) administration of CORT (30 mg kg−1) to male ADX+PSL mice enhances ATP release from spinal slices (means±s.e.m.; n=5). *P<0.05 significantly different from the basal level (F3,16=3.755, P=0.042 for Ipsi.; F3,16=4.933, P=0.018 for Contra.; ANOVA with Tukey–Kramer's PHT). (c) Administration of CORT (30 mg kg−1, s.c.) to male ADX+PSL mice decreases the withdrawal threshold of the ipsilateral hindpaw (means±s.e.m.; n=6). **P<0.01; *P<0.05 significantly different from the basal level (F6,35=2.356, P=0.042; ANOVA with Tukey–Kramer's PHT). (d) Intrathecal (i.th.) injection of ATP (30 nmol per mouse) to male ADX+PSL mice decrease the withdrawal threshold of the ipsilateral hindpaw (means±s.e.m.; n=8). **P<0.01; *P<0.05 significantly different from the basal level (F6,49=3.964, P=0.002; ANOVA with Tukey–Kramer's PHT). (e) The P2Y12 receptor antagonists AR-C69931 (5 pmol per mouse, i.th.) or AZD6140 (10 pmol per mouse, i.th.) prevent CORT (30 mg kg−1, s.c.)-induced pain hypersensitivity in male ADX+PSL mice (means±s.e.m.; n=5–6). *P<0.05; significantly different from other groups (F23,90=1.012, P=0.046; ANOVA with Tukey–Kramer's PHT). (f) Effects of antagonist P2X1–4 receptors TNP-ATP (3 nmol per mouse, i.th.) or antagonist P2Y6 receptor MRS2578 (30 nmol per mouse, i.th.) on CORT (30 mg kg−1, s.c.)-induced pain hypersensitivity in male ADX+PSL mice (means±s.e.m.; n=5–6). *P<0.05; significantly different from other groups (F23,93=1.987, P=0.014; ANOVA with Tukey–Kramer's PHT). (g) The withdrawal threshold of the ipsilateral hindpaw of male sham+PSL mice after the injection of AR-C69931 (5 pmol per mouse, i.th.) or AZD6140 (10 pmol per mouse, i.th.) (means±s.e.m.; n=5–6), **P<0.01, *P<0.05 significantly different from vehicle (0.01% DMSO, 0.01% ethanol in PBS)-treated groups (F14,75=1.965, P=0.033; ANOVA with Tukey–Kramer's PHT). Time of drug administration was set at ZT10. All experiments were performed on day 7 after nerve injury.