Figure 3
Effect of capsaicin treatment on cEPSCs evoked by LPB tract stimulation in the CeC in the neuropathic pain model. A, representative waveforms (averages of 8 to 10 consecutive responses) of cEPSCs evoked by LPB tract stimulation with increasing intensities (from left to right). Top, recordings from a capsaicin-treated rat from left (thin line) and right (thick line) CeC neurons. Bottom, recordings from a vehicle-treated rat. Recordings were from 4 different rats at 7 days after nerve ligation. B, input–output relation between the stimulation intensity (abscissa) and cEPSC amplitude (ordinate). Based on the data from rats at 7–9 days after nerve ligation. Large-size markers indicate the values from neurons in the left CeC (open markers) and the right CeC (filled markers) from the capsaicin- (circles) and vehicle- (triangles) treated SNL groups. Small-size markers indicate those values obtained from non-SNL rats. Mean ± SEM. The number of neurons is indicated in the right-side legends for each group. **, P < 0.01; vs. neurons of all other 7 groups (one-way ANOVA followed by Bonferroni post-hoc correction). *, P < 0.05; vs. right CeC in vehicle-treated SNL rat and vs. both sides of CeCs in capsaicin-treated non-SNL rats (one-way ANOVA followed by Bonferroni post-hoc correction). The numbers in parentheses indicate the number of neurons. C, Comparison of the paired pulse ratio (PPR) of cEPSCs. 1, representative averaged cEPSC waveforms recorded in bilateral CeC neurons from capsaicin- and vehicle-treated SNL rats. Note that the ratio of the first to the second cEPSC amplitude did not essentially change, despite manifest differences in the amplitude both in vehicle- and capsaicin-treated SNL groups. 2, summary of the results of PPR (as measured for cEPSCs evoked by 1-mA stimulation). Left 4 bars, data from SNL rats; right 4 bars, data from non-SNL rats. There were no significant differences between the capsaicin- and vehicle-treated groups in both SNL and non-SNL groups (Mann–Whitney U test). *, P < 0.05; **, P < 0.01 (Mann–Whitney U test) between SNL and non-SNL groups. Mean ± SEM. Numbers in the bars indicate the number of neurons.