The innervation of cholinergic nerves in the Eustachian tube was light- and electron-microscopically observed using a histochemical technique. Acetylcholinesterase -positive nerves were seen just beneath the epithelial layer all along the tubal wall, around the blood vessels of the subepithelial space, and especially around the tubal glands. It is suggested from these findings that the cholinergic nerve plays an important role in controlling the blood flow in the subepithelial space and also in regulating the secretion of the tubal gland.
