Increased levels of substance P and calcitonin gene-related peptide in rat adjuvant arthritis. A combined immunohistochemical and radioimmunoassay analysis.

OBJECTIVE: To analyze the occurrence of substance P (SP) and calcitonin gene-related peptide (CGRP) in ankle joints and corresponding dorsal root ganglia (L2-L6) of rats with adjuvant arthritis. METHODS: Arthritis was induced by inoculation with heat-killed mycobacteria. The morphologic distribution of SP and CGRP was assessed by immunohistochemical analysis. Tissue concentrations of the neuropeptides were determined by radioimmunoassay. RESULTS: Neuronal CGRP-like immunoreactivity was clearly increased in the synovium and the dorsal root ganglia, whereas the increase in SP-positive structures was less pronounced. The tissue concentrations of SP and CGRP were significantly increased both in ankle joints and in dorsal root ganglia. CONCLUSION: Levels of sensory neuropeptides are increased under conditions of joint inflammation.