FOS and arthritic joint disease: In the RA group, the induction of experimental arthritis resulted in higher immunoexpression of c‐Fos in the trigeminal ganglion (Figure 3F,H; mean positive area = 77.7%) and in the Sp5C region (Figure 3G,I; mean positive area = 18.7%) in neuronal cells when compared to the control group (mean positive area = 20.3% and 3.2%, respectively; p < 0.0001), suggesting peripheral and central activation of the trigeminal nociceptive pathway.