The Meissner corpuscle revised: A multiafferented mechanoreceptor with nociceptor immunochemical properties

Meissner corpuscles (MCs) in the glabrous skin of monkey digits have at lea st three types of innervation as revealed by immunofluorescence. The previo usly well known A alpha beta -fiber terminals are closely intertwined with endings from peptidergic C-fibers. These intertwined endings are segregated into zones that alternate with zones containing a third type of ending sup plied by nonpeptidergic C-fibers. Although MCs are widely regarded as low-t hreshold mechanoreceptors, all three types of innervation express immunoche mical properties associated with nociception. The peptidergic C-fiber endin gs have readily detectable levels of immunoreactivity (IR) for calcitonin g ene-related peptide (CGRP) and substance P (SP). The A alpha beta endings h ave relatively lower levels of IR for CGRP and SP as well as the SP neuroki nin 1 receptor and vanilloid-like receptor 1. Both the A alpha beta and pep tidergic C-fiber endings were also labeled with antibodies for different co mbinations of adrenergic, opioid, and purinergic receptors. The nonpeptider gic C-fiber endings express IR for vanilloid receptor 1, which has also bee n implicated in nociception. Thus, MCs are multiafferented receptor organs that may have nociceptive capabilities in addition to being low-threshold m echanoreceptors.