Abstract
Adrenergic innervation of the eustachian tube of the guinea pig pretreated with 5-hydroxydopamine was studied by electron microscope. Adrenergic nerve terminals were not found in the epithelial layer. Two types of adrenergic nerve terminals were found in the lamina propria. One innervated the area along the blood vessel wall and the other ran quite independently of the blood vessel. Most of the adrenergic nerve terminals around the arteries were located just beneath the smooth muscle layer. This finding suggests that blood vessel functions of the eustachian tube are also regulated directly by the autonomic nervous system. The finding of free terminals suggests that some neurotransmitters are released from the free terminals, migrate, and influence effector organs, such as goblet cells of the tubal epithelium. Some of the nerve terminals were observed close to the myoepithelial cells of the tubal gland: however, most of the nerve terminal innervation was detected in the vicinity of the blood vessel close to the eustachian tubal gland. No clear adrenergic innervation was detected in the intraacinal region. Adrenergic nerve terminals were usually observed in the vicinity of the blood vessel close to the paratubal muscle. Interestingly, however, some adrenergic nerve terminals were also observed among the bundles of the paratubal muscle with no relation to the blood vessel. Adrenergic nerve terminals were seldom seen outside the tubal cartilage.
