Temporomandibular joint (TMJ) arthritis was induced in female Lewis ra
ts by unilateral injection of a suspension of heat-killed Mycobacteriu
m butyricum in paraffin oil into the TMJ. Control rats received paraff
in oil by the same route. Arthritic and control rats were pretreated e
ither with capsaicin or denervation of the mandibular branch of the tr
igeminal nerve. Tissues were collected for neuropeptide extraction and
analysed by radioimmunoassay and reverse-phase high-performance liqui
d chromatography. In all groups, the levels of substance P- (SP), calc
itonin gene-related peptide- (CGRP) and neuropeptide Y- (NPY) like imm
unoreactivity (LI) were higher in the trigeminal ganglia than in the T
MJs. In control rats, capsaicin significantly lowered the levels of SP
-LI in the trigeminal ganglia and TMJ, but not CGRP-LI and NPY-LI. In
the arthritic rats, capsaicin pretreatment significantly lowered the S
P-LI and CGRP-LI in the trigeminal ganglia and TMJ; but not the NPY-LI
. In the trigeminal ganglia the unilateral denervation significantly l
owered SP-LI in control rats, and in arthritic rats SP-LI and CGRP-LI.
On the denervated side of the arthritic TMJ, NPY-LI, SP-LI and CGRP-L
I were significantly lowered as compared to the arthritic control rats
and to the contralateral side. In this rat model, pretreatment with c
apsaicin and surgical denervation decreased the neuropeptide content i
n the trigeminal ganglia and the TMJ. The results clearly demonstrate
a close interaction between increased neuropeptide release from sensor
y and sympathetic neurones after induction of arthritis in the rat. (C
) 1997 Elsevier Science Ltd. All rights reserved.