Figure 1

The involvement of supraspinal P2X ₃ /P2X _2/3 receptors in the antinociception produced by i.c.v. administration of α,β-methylene-ATP. The nociceptive thresholds at 5 min after the i.c.v. administration of α,β-methylene-ATP (10 nmol) were compared in the paw pressure test. The nociceptive threshold of each animal before the i.c.v. administration served as the control value (100%), and the values are presented as the means of the % of the control ± S.E.M. (A) The effect of i.c.v. pretreatment with A-317491. α,β-Methylene-ATP or PBS was administered i.c.v. 15 min after i.c.v. pretreatment with A-317491 (0.01–1 nmol) or PBS. ***P < 0.001 vs PBS-PBS group, ^# P < 0.05 vs PBS-α,β-methylene-ATP group (n = 5–8). (B) RT-PCR analyses of the mRNA expression levels for P2X₃ receptor (upper) and β-actin (bottom) in the brainstem after repeated i.c.v. pretreatments with PBS, P2X₃ A-ODN (1 nmol), and P2X₃ S-ODN (1 nmol). (C) The effects of repeated i.c.v. pretreatments with PBS, P2X₃ A-ODN and P2X₃ S-ODN on the antinociception by i.c.v. administered α,β-methylene-ATP. *P < 0.05 (n = 5–6).