NERVE GROWTH-FACTOR RECEPTOR (P75)-IMMUNOREACTIVITY IN THE NORMAL ADULT FELINE TRIGEMINAL SYSTEM AND FOLLOWING RETROGASSERIAN RHIZOTOMY

The 75 kDa protein nerve growth factor receptor [NGFr(p75)] is a neuro trophin receptor that is able to bind different members of the neurotr ophin family of molecules implicated in affecting neuronal survival. H ere we describe the light microscopic distribution of NGFr(p75)-immuno reactivity (IR) within the feline trigeminal brainstem sensory nuclear complex and trigeminal ganglion of normal adult subjects and in subje cts 10 and 30 days following retrogasserian rhizotomy. Within the trig eminal ganglion of normal subjects, numerous fibers and most of the ne uronal cell bodies showed NGFr(p75)-IR that varied in intensity, while cells and fibers with NGFr(p75)-IR were less numerous within the mese ncephalic trigeminal nucleus. Within the main sensory and spinal trige minal nuclei, NGFr(p75)-IR formed a reproducible pattern that varied b etween the different subnuclei. The NGFr(p75)-IR consisted both of den se pockets and a low level NGFr(p75)-IR that was selective to the trig eminal neuropil. Following rhizotomy, most of the NGFr(p75)-IR was los t from the main sensory and spinal trigeminal nuclei, except in region s where the upper cervical roots and cranial nerves VII, IX, and X pro ject. In contrast, examination of the central root that was still atta ched to the trigeminal ganglion showed increased NGFr(p75)-IR in fiber s and supporting cells, as did the motor root within the peripheral ma ndibular division. These results indicate that the majority of the NGF r(p75)-IR within the main sensory and spinal trigeminal nuclei origina tes from primary trigeminal afferents and that retrogasserian rhizotom y leads to an up-regulation of NGFr(p75)-IR in the part of the central root that is contiguous with the ganglion. (C) 1993 Wiley-Liss, Inc.