DISTRIBUTION OF SUBSTANCE-P IMMUNOREACTIVE NERVE-FIBERS IN THE TRACHEAL SUBMUCOSAL GLAND OF CATS

Immunohistochemistry combined with electron microscopy was employed to investigate the distribution of substance P-immunoreactive (SP-IR) ne rve fibers in the tracheal submucosal gland of cats. The SP-IR nerve f ibers were found to form a network around the glands. Numerous varicos ities were also detected within the basement membrane of the acini and secretory tubules. All the intraglandular varicosities showed close s patial contact with serous cells, mucous cells, and myoepithelial cell s. Our findings suggest that substance P-induced mucus secretion from tracheal submucosal glands in cats may be caused not only by a glandul ar contractile response of myoepithelial cells, but also by direct sti mulation to both serous and mucous cells.