NEUROPEPTIDE Y-LIKE AND VASOACTIVE INTESTINAL POLYPEPTIDE-LIKE IMMUNOREACTIVITY IN ADJUVANT ARTHRITIS - EFFECTS OF CAPSAICIN TREATMENT

The occurrence of the neuropeptides vasoactive intestinal polypeptide (VIP) and neuropeptide Y (NPY) in ankle joints and dorsal root ganglia (L2-L6) was analyzed in normal and arthritic Lewis rats. In addition the effect of capsaicin pretreatment was investigated. The study inclu ded 92 rats consisting of 4 groups, 23 rats in each; normal rats, norm al rats given capsaicin, arthritic rats and arthritic rats pretreated with capsaicin. The localization of the neuropeptides was assessed by immunohistochemistry and the tissue concentrations were determined by radioimmunoassay (RIA). In the arthritic rats, there was a slight incr ease in NPY immunoreactive nerve fibres in the ankle joint synovium an d bone marrow, as compared to normal rats. Notably, there was an inten se fluorescence and significant increase (p <0.01, 41%) in the number of NPY-positive megakaryocytes in the tibial bone marrow of arthritic rats. RIA showed that the concentration of NPY-like immunoreactivity ( LI) was increased by 50% in the ankle joint. Pretreatment with capsaic in did not affect the increased level of NPY-LI in the ankle joint of arthritic rats. The concentration of NPY-LI in the dorsal root ganglia was not altered in arthritic rats, nor was it affected by the capsaic in treatment. No NPY immunoreactive cells could be detected in the dor sal root ganglia. The number of VIP immunoreactive nerve fibres observ ed in ankle joints of arthritic and normal rats did not differ. Howeve r,, RIA measurements showed an 11% increase in the VIP concentration i n arthritic rats, which was unaffected by capsaicin treatment. In dors al root ganglia, RIA disclosed a 21% increase in VIP-LI, although no V IP-positive cells could be detected. Capsaicin treatment did not affec t the increased concentration of VIP-LI in the dorsal root ganglia.