Characteristic intraepidermal nerve fibre endings of the intervibrissal fur in the mystacial pad of the rat: morphological details revealed by intravital methylene blue staining and the zinc iodide-osmium tetroxide technique

The study used intravital methylene blue staining and the zinc iodide-osmium tetroxide technique to examine intraepidermal nerve fibre endings in the mystacial pad of rat snouts. These methods revealed detailed anatomical structures of nerve fibre plexuses near hair follicles, resembling cluster or bush endings from previous studies. The methylene blue staining highlighted an intensely stained enlargement at nerve fibre branching points, suggesting a functional role in nerve plexus development. The nerve fibres were likely mechanoreceptive due to their proximity to hairs. Additionally, solitary varicose nerve fibres were observed in the epidermis. The study extended the concept of punctate sensibility into the epidermis and found methylene blue staining to be superior in visualizing these structures, complementing immunohistochemical techniques.