Three dimensional observations of the palisade-shaped nerve endings of normal hair of rat's snout.

The nerve endings of normal hair of the rat's snout, partially digested with trypsin and hydrochloric acid, were studied by scanning electron microscopy. Each lanceolate structure measured ca. 10 microns in length and was arranged around the hair follicle. These palisade-shaped nerve endings were situated almost beneath the sebaceous glands, ran upward, parallel to the axis of the hair follicle, and terminated in pointed shape. 2 kinds of cells, Teloglia cell Type I showing flat profile, and Teloglia cell Type II showing spherical profile and possessing numerous caveolae in its surface were observed at the basal portion of the palisade-shaped endings. The axon was enclosed by Schwann cells in its course to the hair follicle, and was covered with Type I cells at the beginning, and with Type II cells at the end, and constituted the palisade-shaped nerve endings. The palisade structure in silver impregnated tissues observed by backscattered electron microscopy and X-ray analyzer was characterized as comprising neuronal elements. Cytochemically, the nerve endings showed cholinesterase and Mg-ATPase activities. They may be involved in the reception of the mechanical stimulation of the hair. The palisade nerve endings thus possessed appropriate 3-dimensional structure as mechanoreceptor.