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 investigated intraepidermal nerve fibre endings in the intervibrissal fur of the rat's mystacial pad using intravital methylene blue staining and the zinc iodide-osmium tetroxide technique. These methods revealed detailed anatomical structures of nerve fibre plexuses near hair mouths, resembling cluster or bush endings from previous studies. The methylene blue staining showed an intensely stained enlargement at nerve fibre branching points, suggesting a functional role in nerve plexus development. These plexuses 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 to the zinc iodide-osmium tetroxide technique. These methods complemented immunohistochemical procedures by selectively targeting intraepidermal nerve fibres.