[Peptidergic innervation in the sinus hair follicles of several mammalian species].

This study investigated the distribution of peptidergic nerve fibers in sinus hair follicles across several mammalian species, including cats, dogs, hamsters, rats, mice, and guinea pigs. Using immunohistochemical methods, researchers identified three types of peptide-immunoreactive (IR) nerve fibers based on their entry and distribution patterns within the follicles. Type A fibers innervated the upper portion of the follicle, Type B fibers formed a dense plexus in the connective tissue follicle, and Type C fibers innervated the hair papilla and hair bulb. Calcitonin gene-related peptide (CGRP) and substance P (SP) were present in all fiber types across all species, with CGRP fibers being more numerous. Vasoactive intestinal polypeptide (VIP) and neuropeptide Y (NPY) fibers were mainly found in types B and C in cats, dogs, and hamsters. The study highlighted species-specific differences in the extension of connective tissue and nerve fiber distribution, particularly noting the well-developed fibers in cats.