ULTRASTRUCTURE AND CYTOCHEMISTRY OF HUMAN CUTANEOUS NERVES.

Autonomic cutaneous nerves showing both agranular and dense core vesicles were found ending in the vicinity of smooth muscle cells (myoneural junctions). Sensory nerve preterminals contained numerous mitochondria, ending at the dermoepidermal interface either with or without Merkel cells (epithelioneural junctions), or in encapsulated organs in the dermis. No free epidermal or dermal endings were seen under the electron microscope. Although such endings may occur, it seems reasonable to suggest that contact zones rather than free axonal endings are the main pathways for skin innervation. Cytochemically, activity of nonspecific cholinesterases was demonstrated in numerous dermal axons and in pinocytotic vesicles in some cells of the vascular walls. Acetylcholinesterase activity was found limited to axons innervating smooth muscle and in pinocytotic vesicles of the smooth muscle cells. The periodic acid-silver methenamine (PASM) reaction revealed a thin layer of silver grains on the axolemma of nonmyelinated nerves, indicating the presence of glycoproteins at this level, whereas the axoplasm showed no affinity for silver before and after treatment with periodic acid. In specimens treated with alcian blue and lanthanum, a similar coat was seen occasionally on the axolemma of thin subepidermal nerves. The perineural sheath was a sufficient barrier for the penetration of lanthanum. In the axoplasm, abundant glycogen granules may be present, whereas no peroxidase or acid phosphatase activity was detected. [ABSTRACT FROM AUTHOR]