Fig. 4. Spontaneous activity of nociceptors 1 day after sham procedure, skin, or skin plus deep tissue incision and 7 days after skin plus deep tissue incision. (A ) Digitized oscilloscope trace of spontaneous action potentials of a C-nociceptor from a rat 1 day after skin plus deep tissue incision. Inset shows a representative single action potential. (B ) Percentage of nociceptors with spontaneous activity in each of the four groups. Chi-square test with Bonferroni post hoc correction for comparisons among groups. (C ) Comparison of average spontaneous activity rates among groups. POD = postoperative day; Imp = impulse. *P < 0.5, **P < 0.01.