Figure 2.

The effect of systemic tapentadol on WDR neuronal responses in MIA and sham animals. (a) Tapentadol restored neuronal inhibition induced by DNIC in MIA animals; for all doses (1 mg/kg n = 8, 2 mg/kg n = 6, and 5 mg/kg n = 7) there was a significant reduction in neuronal firing in response to a 60 g mechanical stimulation in the presence of a conditioning noxious ear pinch, while 2 and 5 mg produced a significant reduction in neuronal firing induced by DNIC in response to a 26 g mechanical stimulation. Tapentadol also dose‐dependently inhibited pre‐conditioned mechanically evoked neuronal responses, but this effect was only significant for the most noxious 60 g stimulation. (b) Tapentadol had little effect on the magnitude of neuronal inhibition induced by DNIC in sham controls as the degree of inhibition remained comparable before and after tapentadol administration for all doses tested (n = 6 for all doses). Tapentadol inhibited pre‐conditioned mechanically evoked neuronal responses in sham animals but this effect was not significant for any doses or mechanical forces tested. Two‐way ANOVA with Bonferroni correction tested statistically significant differences from pre‐conditioned baseline responses for both DNIC‐induced and drug‐induced neuronal inhibition; *p < 0.05, **p < 0.01, ***p < 0.001