Change of PACAP receptor expressing cells during the development of granular duct in male mouse submandibular glands.

Saliva secretion is mainly controlled by autonomic nervous system. Pituitary adenylate cyclase activating polypeptide (PACAP) is now recognized as the multi‐functional neuropeptide in various organs. We previously compared the distribution of PACAP receptor (PAC1R) in three major salivary glands of young and old male C57BL/6 mice. The distribution of PAC1R in the glands was not different by age. In submandibular gland, PAC1R was detected in the tall columnar epithelial cells, called pillar cells, in granular ducts and some of the cells in the striated ducts. The granular duct is characteristic in rodents. In this study, we examined the expression of PAC1R with the development of mouse submandibular gland. The submandibular glands at 1,3,5,7 days‐old and 2,3,4,8 weeks‐old male C57BL/6 mice were used for the immunohistochemical detection of PAC1R. Granular duct was not identified until 3 weeks after birth. PAC1R was detected in the striated duct by 2 weeks. At 3 weeks, granular duct was clearly identified and PAC1R was expressed in the pillar cells of the duct. After 4 weeks, PAC1R was more strongly detected at pillar cells than 3 weeks. These results indicated that the distribution of PAC1R was changed from striated duct to pillar cells with the formation of granular duct. A precise study might be necessary to clarify the function of pillar cells by examining the shift of PAC1R‐positive cells in the submandibular gland.