Characteristic Intraepidermal Nerve Fiber 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 enlargement at nerve fibre branching points, suggesting a role in nerve plexus development. The nerve fibres were likely mechanoreceptive due to their proximity to hairs. Two types of nerve fibre endings were identified, supporting the concept of punctate sensibility in the epidermis. Methylene blue staining was found to be more effective than the zinc iodide-osmium tetroxide technique, and both methods complemented immunohistochemical procedures by selectively targeting intraepidermal nerve fibres.