A model for experimentally induced temperomandibular joint arthritis in rats: effects of carrageenan on neuropeptide-like immunoreactivity.

Substance P(SP)-, neurokinin A (NKA)-, calcitonin gene-related peptide (CGRP)- and neuropeptide Y (NPY)-like immunoreactivity (-LI) was studied in rats' cerebrospinal fluid (CSF), plasma and perfusates (PF) from the temporomandibular joints (TMJs) at 2, 6 and 24 h following 0.01 ml injection of 2% carrageenan (CAR) into the right TMJ. SP-, NKA-, CGRP- and NPY-LI were significantly increased in both TMJ perfusates of the treated groups compared to controls. Generally an injection with CAR into the right TMJ induced a similar influence of the concentration of SP-, NKA-, CGRP- and NPY-LI in the CSF, plasma and PF at 2, 6 and 24 h following injection. However, the most pronounced changes in neuropeptide-LI occurred intra-articularly in the joint fluid, which indicates that both the sensory and sympathetic nervous system are activated in this joint following osteoarthritis induction by carrageenan.