Effects of DAMGO on discharges of C fibres with elevated mechanical thresholds in injured nerves. (A) Representative examples of C fibre firing (upper panels) and quantitative analysis (lower panels) showing that baseline discharge rates of C nociceptors to nanomotor stimulation were diminished by DAMGO (100 μM) (*P < 0.05; 2-way RM ANOVA, Bonferroni t test), but not by control buffer (P > 0.05; 2-way RM ANOVA). DAMGO and buffer were tested on separate sets of fibres. In upper panels the displacements are marked with dark lines, and the interstimulus sequences are removed. (B) DAMGO (100 μM)-induced reduction in the discharge rate was reversed by DAMGO washout and prevented by pre-application of CTOP (100 μM). This was tested in additional C fibres at a single nanomotor stimulation (384 μm). ∗
P < 0.05, compared to all other conditions (1-way RM ANOVA; Bonferroni t test). All data are expressed as means ± SEM. N, number of fibres.