Morphological Study of Vagal Innervation in Human Semilunar Valves Using a Histochemical Method

To determine the innervation of human semilunar valves, we examined the pulmonary and aortic valves of the normal autopsied hearts of 3 men (53 to 71 years old). Whole valve tissues with the aorta or pulmonary trunk were stained for acetylcholinesterase by a histochemical method. Acetylcholinesterase-positive nerve fibers with a diameter of 2 to 20 mm were located on the ventricular side of the semilunar valves. Innervation of the semilunar valves was extremely sparse compared with that of the atrioventricular valves and that of the aortic or pulmonary arterial wall. The nerves originated from the subendocardium of the ventricles and the adventitia of the arterial walls. The nerves were more distributed in the basal site than in the marginal site of the semilunar valve. The nerve fibers formed a network in basal two-thirds of the leaflet. Thick nerves ramified in the thin nerve plexus. The thick nerves had a varicose-like structure. Thin nerves had a dot- and brush-like ending. The nerves in human semilunar valves may play a role in valve motion.