Calcitonin gene related peptide gene expression in collagen-induced arthritis

Changes in calcitonin gene related peptide (CGRP) gene expression in spinal motoneurons and dorsal root ganglia (DRG) of rats subjected to collagen II induced arthritis (CIA) were evaluated by semiquantitative in situ hybridization. The effects of systemic treatment with the corticosteroid budesonide on basal CGRP expression and on changes under inflammatory conditions were examined. CIA caused a significant increase in CGRP mRNA levels in DRG. Budesonide reduced the constitutive CGRP mRNA levels in DRG, compared with untreated control rats, and reversed the CIA-induced increase. In contrast, CIA caused a marked decrease of CGRP mRNA levels in motoneurons. Budesonide had no effect on constitutive CGRP mRNA levels in motoneurons and attenuated the decrease in CGRP mRNA levels in motoneurons of rats subjected to CIA. Thus, peripheral inflammation and systemic corticosteroids have differential effects on CGRP expression in sensory and motor neurons. This may be relevant for the pathophysiology and pharmacotherapy of chronic inflammatory pain and motor dysfunction in chronic arthritis.