[Ultrastructural features of the interrelationship between nerve fibers and the surrounding tissue in the major arteries of rabbits].

The fine structure of nerve plexus in the rabbit abdominal aorta, ear and coronary arteries has been studied. Four types of the nerve fibre organization corresponding to different levels of sectioning their preterminal and terminal zones have been determined. Axons form large bundles which lose Schwann sheathes and divide into smaller and even single axons as they approach the distal end. Single axons make up contacts with effector cells without forming special synaptic structures. The smalles distance found between axon membranes and smooth muscle cells is 20 nm and 50 nm for the ear and coronary arteries, respectively. In the abdominal aorta, axons lie at a distance of several microns from the muscle sheath. Such arrangement supports the hypothesis of a "distant" nervous influence on the smooth muscle and indicates that the space of nervous influence comprises the tissue surrounding the blood vessel