Irradiation-induced effects on the innervation of rat salivary glands: Changes in enkephalin- and bombesin-like immunoreactivity in ganglionic cells and intraglandular nerve fibers

When treating head and neck for cancer with the use of radiotherapy the salivary glands are usually within the treatment volume with ensuing dryness and discomfort. Since the autonomic nervous system is of pivotal importance for the salivary gland function and integrity, the irradiation-induced effects may involve an influence on the innervation of salivary glands. Therefore, the rat submandibular gland, including the submandibular ganglionic cells, has been subjected to immunohistochemical examination with respect to expression of neuropeptides following fractionated irradiation with high energy photons. A markedly enhanced expression of bombesin- and leu-enkephalin-(ENK)-like immunoreactivities (LI) in the ganglionic cells and a pronounced increase in the number of nerve fibers showing these immunoreactivities in the submandibular gland tissue following irradiation were observed 10 days after treatment. On the other hand, no changes in the patterns of VIP (vasoactive intestinal polypeptide)- and NPY (neuropeptide Y)-immunoreactivities occurred. Thus, the present study shows that alterations in the expression of certain neuropeptides take place in the submandibular gland and its associated ganglionic cells in response to irradiation of the head and neck region. These changes may add further explanation to the inherent radiosensitivity of salivary glands.