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. 2024 Jan;25(1):88–100. doi: 10.1016/j.jpain.2023.07.023

Figure 3.

Figure 3

A-fibers that retained mechanical responsiveness after oxaliplatin exhibit increased firing rates and altered adaptation properties. The number and frequency of action potentials discharged during 10 seconds mechanical stimuli are increased post oxaliplatin (blue circles) treatment compared to pretreatment (red circles) baseline and post vehicle control values (black circles). (A) AM fibers that retained responsiveness after exposure to oxaliplatin (600 µM in SIF) fired significantly more action potentials during the 4 g step stimulus compared to vehicle-treated units and compared to pretreatment (*P < .05, Mixed-effects analysis followed by Tukey’s test, n = 8–10 fibers). (B) AM fibers treated with oxaliplatin displayed altered adaptation patterns, such as firing after removal of the 4 g stimulus (n = 5/7), which was not seen before treatment. (C) Average adaptation properties to 4 g, 10 seconds mechanical force step from all AM fibers tested (***P < .001, Wilcoxon’s test, n = 10). (D) AβRA fibers fired more action potentials during 15 g steps after oxaliplatin treatment compared to vehicle-treated units and compared to pretreatment (Mixed-effects analysis followed by Tukey’s test, n = 6–7 fibers). (E) Oxaliplatin changed the adaptation of AβRA fibers (observed in 3 of the 6 units), which typically do not fire throughout the mechanical stimulus (pretreatment and postvehicle control). Some oxaliplatin-treated AβRA fibers also fired after the removal of mechanical stimulus (2/6). (F) Average adaptation properties in response to 15 g, 10 seconds mechanical force step from all AβRA fibers tested (Wilcoxon’s signed rank test, n = 7). (G) AβSA fibers retained their adaptation properties but fired more action potentials after oxaliplatin in response to 15 g force steps compared to post vehicle and preoxaliplatin (Mixed-effects analysis followed by Tukey’s test, n = 10). (H) Representative trace of AβSA activity during a 15 g mechanical stimulus. (I) The average adaptation properties of AβSA fibers (n = 10) demonstrate an increased firing rate, particularly at the beginning and end of the mechanical stimulation (Wilcoxon’s signed rank test, n = 10). Abbreviation: AβSA, Aβ slowly adapting fiber.