Innervation of Vasa Nervorum

Abstract

This chapter reviews the anatomy of the circulation in nerves with emphasis on its regulation by nonadrenergic, noncholinergic neuroeffector mechanisms. Endoneurial vasa nervorum branch symmetrically and repeatedly and consist only of capillaries. Vasa nervorum are composed of the same elements as other blood vessels, but their ultrastructural features are less well defined. Vasa nervorum are encircled by connective tissue containing substantial extracellular space. The permeability of vasa nervorum regulates the passage of metabolites, toxins, and other substances to nerves, and it is therefore important in blood-nerve barrier function in health and disease. The innervation of vasa nervorum and the role of neurotransmitters in nervi nervorum has been largely ignored. Serotoninergic innervation of vasa and nervi nervorum may therefore be important in maintaining the integrity of the blood-nerve barrier and in hom-eostatically regulating the peripheral and cranial nerve environment. Clinical and experimental observations show a relationship between blood vessels supplying blood to nerves and peripheral nerve dysfunction in pathological states.