Nerve growth factor receptor immunoreactivity in Meissner and Pacinian corpuscles of the human digital skin

The presence of nerve growth factor receptors (NGFr) in sensory nerve corpuscles of human digital skin, primarily Meissner and Pacinian corpuscles, was investigated immunohistochemically using two monoclonal antibodies directed against human-NGFr. To ensure the localization of NGFr immunoreactivity (IR) alternative sections to that processed for NGFr detection were assayed for neurofilament protein (NFP) and S-100 protein which selectively label the axon and the periaxonic specialized cells (lamellar cells of Meissner's corpuscles; inner-core cells of Pacinian corpuscles), respectively. Occurrence of NGFr IR was observed in both types of sensory corpuscles. In Meissner's corpuscles NGFr-IR was found in the lamellar cells, whereas in the Pacinian corpuscles the lamellae of the inner core, outer core, and capsule displayed NGFr IR. Moreover, a positive IR was observed in the central axon of some Pacinian corpuscles. However, remarkable differences were encountered among Pacinian corpuscles in the pattern of NGFr IR distribution. Present results demonstrate the presence of NGFr IR in sensory nerve corpuscles of the human digital skin, suggesting that NGFr could be involved in the concentration of NGF and in the conveying of this molecule from the cutaneous sources to the cell body of NGF-dependent primary sensory neurons. However, the mechanisms involved in this process remain to be clarified.