Immunohistochemical reactions of receptors to met-enkephalin, VIP, substance P, and CGRP located on Merkel cells in the rat sinus hair follicle.
The role of Merkel cells in type I cutaneous mechanoreceptors remains enigmatic though mechanical transduction or neuromodulation function has been proposed. It has been shown that mammalian Merkel cells express immunohistochemical reactions of met-enkephalin, VIP, substance P, and CGRP, though the reactivity differs between species. If any one of these peptides acts as a transmitter or modulator for Merkel nerve terminals, these structures must have a specific receptor for the substance. We therefore studied the immunohistochemical localization of the above-mentioned neuropeptides and their receptors in Merkel cell-nerve endings in rat whisker pads. Specimens were doubly stained with polyclonal antibodies to neuropeptides and their receptors combined with a monoclonal antibody to cytokeratin 20, which was used for the labeling of Merkel cells. Merkel cells in the rat sinus hair follicles showed positive immunoreactions for all peptides studied, whereas the immunoreactions of receptors to these peptides were localized on Merkel cell membranes but not on the axon terminals. These results suggest that neuropeptides released from Merkel cells act on Merkel cells themselves by an autocrine mechanism.
Tachibana
Tamiko
T
Department of Oral Anatomy II, Iwate Medical University School of Dentistry, Morioka 020-8505, Japan. tatamiko@iwate-med.ac.jp
Nawa
Tokio
T
D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism*; D004744:Enkephalin, Methionine / Q000378:metabolism*; D005260:Female; D018859:Hair Follicle / Q000166:cytology / Q000294:innervation / Q000378:metabolism*; D007150:Immunohistochemistry; D053554:Keratin-20; D007633:Keratins / Q000378:metabolism; D008297:Male; D018862:Merkel Cells / Q000378:metabolism* / Q000648:ultrastructure; D018613:Microscopy, Confocal; D051381:Rats; D013373:Substance P / Q000378:metabolism*; D014660:Vasoactive Intestinal Peptide / Q000378:metabolism*; D014738:Vibrissae / Q000166:cytology / Q000294:innervation / Q000378:metabolism
D000911:Antibodies, Monoclonal; D053554:Keratin-20; D013373:Substance P; D014660:Vasoactive Intestinal Peptide; D004744:Enkephalin, Methionine; D007633:Keratins; D015740:Calcitonin Gene-Related Peptide