Bradykinin (BK)- and N-oleoyldopamine (OLDA)-induced thermal hyperalgesia was prevented by TRPV1 antagonist pretreatment. (A) Intrathecal (i.t.) administration of a relatively low dose of TRPV1 endogenous agonist OLDA (0.42 µg, n = 4) did not change the paw withdrawal latency (PWL), as compared to vehicle-treated rats (n = 6). (B) Administration of BK (21.2 μg, i.t., n = 6) transiently decreased the PWL, as compared to vehicle-treated rats. (C) Co-administration of both BK (21.2 μg) and OLDA (0.42 µg, i.t., n = 6) enhanced the hyperalgesic effect induced by BK alone. (D) Thermal hyperalgesia induced by BK and OLDA co-administration was prevented by selective TRPV1 antagonist SB366791 pretreatment (SB, 0.58 µg, i.t., 15 min, n = 7). Data represent the mean ± S.E.M. of 4–7 independent experiments. Statistical analysis: Mann-Whitney rank test; ** p < 0.01, *** p < 0.001 left hindpaw (L), BK versus vehicle treatment; #
p < 0.05, ##
p < 0.01, ###
p < 0.001 right hindpaw (R), BK versus vehicle treatment. The time of the i.t. administration is marked by arrows.