Changing of the immunoreactive nerve fibers in the tongue after transection of the lingual nerve

Background, Aims: Previous literature data showed that there are primary sensory neurons in different organs (e.g. gastrointestinal tract, urinary bladder). In our previous studies we also demonstrated some substance P (SP) immunoreactive (IR) nerve cell bodies in the root of the rat tongue. Therefore, our aim was to investigate the effect of the transection of the lingual nerve on the distribution and density of the different IR nerve fibers in the root of the tongue from rats.

Methods: Vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY), substance P (SP), galanin and calcitonin gene-related peptide (CGRP) and tyrosine beta-hydroxylase (TH) IR nerve elements were detected by ABC immunohistochemistry.

Results: The quantitative analysis of the density of the different neuropeptide containing nerve fibres showed that the IR nerve fibres were found in all layers with different density. The SP and galanin IR nerve fibres were mainly located in the subepithelial layer as well as in the epithelium close to and in the taste buds. However the VIP and NPY IR nerve fibres were observed mainly around the salivary acini and blood vessels. After cutting the lingual nerve the number of all of the investigated nerve fibres were decreased, where the number of SP IR nerve fibres was decreased significantly (p<0.05). Some SP, VIP, NPY and a few galanin IR nerve cell bodies were observed in the wall. Some SP IR nerve fibres were found in a very close situation to the other immunonegative neurons. Some immunocytes showed also immunoreactivity for galanin after cutting the lingual nerve. Conclusions: These results suggested that intrinsic intraligual reflex might exist in the tounge, where the afferent branch of the reflex contained SP and galanin, the efferent branch worked with NPY and VIP.