The aim of this study was to identify immunoreactive neuropeptide Y (NPY) and calcitonin gene-related peptide (CGRP) neurons in the autonomic and sensory ganglia, specifically neurons that innervate the rat temporomandibular joint (TMJ). A possible variation between the percentages of these neurons in acute and chronic phases of carrageenan-induced arthritis was examined. Retrograde neuronal tracing was combined with indirect immunofluorescence to identify NPY-immunoreactive (NPY-IR) and CGRP- immunoreactive (CGRP-IR) neurons that send nerve fibers to the normal and arthritic temporomandibular joint. In normal joints, NPY-IR neurons constitute 78Â±3%, 77Â±6% and 10Â±4% of double-labeled nucleated neuronal profile originated from the superior cervical, stellate and otic ganglia, respectively. These percentages in the autonomic ganglia were significantly decreased in acute (58Â±2% to superior cervical ganglion and 58Â±8% to stellate ganglion) and chronic (60Â±2% to superior cervical ganglion and 59Â±15% to stellate ganglion) phases of arthritis, while in the otic ganglion these percentages were significantly increased to 19Â±5% and 13Â±3%, respectively. In the trigeminal ganglion, CGRP-IR neurons innervating the joint significantly increased from 31Â±3% in normal animals to 54Â±2% and 49Â±3% in the acute and chronic phases of arthritis, respectively. It can be concluded that NPY neurons that send nerve fibers to the rat temporomandibular joint are located mainly in the superior cervical, stellate and otic ganglia. Acute and chronic phases of carrageenan-induced arthritis lead to an increase in the percentage of NPY-IR parasympathetic and CGRP-IR sensory neurons and decrease in the percentage of NPY-IR sympathetic neurons related to TMJ innervation.
trigeminal ganglion, otic ganglion, superior cervical ganglion, arthritis, temporomandibular joint