Immunohistochemical characterisation of neurons in the mandibular ganglion and nerve fibres supplying the porcine mandibular gland

The present study was designed to investigate the chemical coding of neurons in the mandibular ganglion (MGn) and nerve fibres supplying the porcine mandibular gland (MGl) with the use of immunofluorescence and RT-PCR. The cryostat sections from MGn and MGl were processed for double-labelling immunohistochemistry using antisera against vesicular acetylcholine transporter (VAChT), choline acetyltransferase (ChAT), dopamine β-hydroxylase (DβH), neuronal nitric oxide synthase (nNOS), vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY), galanin (GAL), substance P (SP) and calcitonin gene-related peptide (CGRP). The MGl was found to be richly supplied by VAChT-positive nerve fibres that surrounded intra- and interlobular salivary ducts. A large number of VAChT-immunoreactive (VAChT-IR) nerve terminals were also observed around acini. Many periductal and periacinar nerve fibres stained positive for DβH. Immunoreactivity to GAL, NPY or VIP was observed in an intermediate number of nerve terminals which were associated with both salivary ducts and acini. Double-immunostaining revealed that in MGn nearly all neurons stained positive for VAChT/ChAT (98.45 ± 0.59%, mean ± SEM) and nNOS (99.71 ± 0.18%). An intermediate number of the nerve cell bodies displayed immunoreactivity to NPY or VIP (18.67 ± 0.52% and 8.11 ± 0.36%, respectively). Single GAL-IR and CGRP-positive neurons were also observed. RT-PCR revealed the presence of transcripts of ChAT, VAChT, nNOS, NPY, VIP and GAL. For SP and DβH very weak signals were observed. RT-PCR with primers targeting CGRP did not generate any PCR product.