Light and electron microscopic distribution of nerve growth factor receptor-like immunoreactivity in the skin of the rat lower lip.

Nerve growth factor receptor distribution in the skin of the adult rat was studied by immunocytochemistry with the use of the monoclonal antibody 192-IgG. Immunoreaction occurred in a patchy pattern in the epidermis and outer root sheaths of hair follicles, as well as in nerves and in capsulated and non-capsulated sensory receptors. Electron microscopic analysis revealed that the areas of patchy epithelial immunostaining corresponded to the plasma membrane of groups of keratinocytes, which were always associated with intra-epithelial nerve fibres. Immunostaining was also associated with Merkel cells, hair follicle receptors, and the capsular cells of capsulated receptors. In the nerves, immunostaining was detected in perineurial cells and axons. After sensory denervation of the skin, immunostaining decreased considerably in the epithelia, as well as in the small nerves, although short segments of increased staining were observed in the latter. In larger nerves, immunostaining was markedly increased and mainly associated with newly formed Schwann cell processes. After sympathetic denervation, the pattern of immunostaining was identical to controls, except for augmented immunoreactivity in short segments of degenerating nerves around blood vessels and smooth muscle fibres. From these observations, it is suggested that the epithelial and perineurial cells synthesize and express nerve growth factor receptors, while receptors present in nerve fibres originate from the nerve cell bodies in the gasserian ganglion.