Nerve growth factor receptor (NGFR)-like immunoreactivity in the perineurial cell in normal and sectioned peripheral nerves of rats.

The occurrence of nerve growth factor receptor (NGFR)-like immunoreactivity in the perineurial cells of sympathetic and sensory nerves was analyzed in normal controls and after surgical severance. In the normal nerve trunk, no cellular elements exhibited NGFR-like immunoreactivity. Immunoreactivity was induced in the innermost perineurial cells and in all Schwann cells distal to a severed nerve. The acquisition of immunoreactivity in perineurial cells was also seen in deafferented sympathetic ganglia. On the other hand, the perineurial cells as well as axonal endings showed NGFR-like immunoreactivity consistently in the terminal region of normal nerves, and this immunoreactivity was enhanced by nerve section. The present study clearly showed that different types of nerve terminals are ensheathed to different extents by perineurial cells which were first clearly identified by their NGFR-like immunoreactivity: 1) nerve terminals were free of the perineurium far away from targets in the iris, 2) they were free of the perineurium at sites close to targets in the lingual epithelium, and 3) the perineurium ensheathed nerve terminals together with targets in Meissner's sensory corpuscle. The functional significance of the three different patterns of perineurial enclosure requires further examination.