Localization of nerve growth factor receptor immunoreactivity in the trigeminal nucleus of kittens

A monoclonal antibody raised against the human nerve growth factor receptor (NGFr) was used to map the distribution of NGFr-immunoreactivity (IR) in the trigeminal nuclear complex of 8- to 10-week-old, immature felines. Somata and fibers show NGFr-IR within the trigeminal ganglion and the mesencephalic trigeminal nucleus. NGFr-IR is also found in fibers within the trigeminal root entry zone, the spinal trigeminal tract, and in fibers and terminals within all the central trigeminal sensory nuclei. The NGFr-IR found within the trigeminal sensory nuclei typically occurs in circumscribed zones that vary in position for the different subnuclei. NGFr-IR is found in the dorsomedial and ventrolateral subdivisions of the main sensory nucleus, in the dorsomedial and occasionally in ventral positions within pars oralis, in dorsal and ventral regions within pars interpolaris, and primarily in outer lamina II with fibers that project to lamina V within pars caudalis/medullary dorsal horn. These results show some overlap with the central distribution of trigeminal primary afferent nociceptive fibers such as those found from the tooth pulp and overlap with the central distribution of such peptides as calcitonin gene-related peptide and substance P, but NGFr-IR is more restricted. Thus, it appears that NGFr-IR is associated with the endings of primary afferent fibers in the brain stem, and that these fibers may represent a certain subclass of primary afferent nociceptors. It is speculated that fibers showing NGFr-IR may have the ability to alter their response to peripheral deafferentation when compared to fibers lacking NGFr-IR.