PGE₂-G sensitized C-fiber nociceptors in HbAA-BERK control mice. PGE₂-G (23 nmol/10 μL) was administered intraplantarly. (A) PGE₂-G evoked activity in C-fiber nociceptors in HbAA-BERK control mice compared with vehicle injection (F[4, 68] = 11.4; P < .005, 2-way ANOVA for repeated measures, treatment × time, N = 12 for vehicle, N = 10 for PGE₂-G). Different from vehicle at *P < .05, **P < .01, ***P < .005. Different from time 0 (preinjection) at #P < .05, ###P < .005, ####P < .001 (Bonferroni t test). (B) PGE₂-G decreased the threshold for response to a mechanical stimulus compared with vehicle (F[1, 20] = 20.2; P < .001, 2-way ANOVA for repeated measures for treatment, N = 12 for vehicle, N = 10 for PGE₂-G). Mechanical response thresholds (millinewtons) were converted to percent change scores to enable parametric analyses. Different from vehicle at *P < .05, ***P < .005. (C) PGE₂-G also increased responses evoked by a 149-mN von Frey monofilament (F[4, 68] = 4.5; P < .005, 2-way ANOVA for repeated measures, treatment × time). Different from vehicle at *P < .05, **P < .01. Different from time 0 at ##P < .01, ###P < .005, ####P < .001. (D) Representative examples of raw data demonstrating conduction latencies characteristic of C-fibers as well as changes in spontaneous activity and response to the 149-mN stimulus following injection of PGE₂. Top, conduction latencies: multiple traces were overlapped to show consistency. The left arrow indicates the onset of the stimulus; the right arrow indicates the action potential of the fiber of interest. Middle, raw traces of 2 C-fiber nociceptors before and after treatment with vehicle or PGE₂-G showing spontaneous activity. Bottom, representative raw data demonstrating responses to a 149-mN stimulus applied for 5 seconds. (E) Intraplantar PGE₂-G administration decreased the threshold response to heat (F[4, 16] = 14.8; P < .001, ANOVA for repeated measures, N = 5). Different from time 0 at *P < .05, **P < .01 (Fisher least significant difference). (F) Intraplantar PGE₂-G administration increased cold thresholds (increased temperature for response) (F[4, 16] = 3.7; P < .05, ANOVA for repeated measures, N = 5). *Different from P < .05 vs time 0. (G) Raw traces of a C-fiber nociceptor that did not respond to cold during initial characterization, but responded to cold following PGE₂-G administration.