DISTRIBUTION OF THE 75-KD LOW-AFFINITY NERVE GROWTH-FACTOR RECEPTOR IN THE PRIMATE PERIPHERAL NERVOUS-SYSTEM

Disruption of the 75-kD low-affinity nerve growth factor (NGF) recepto r (p75) has been shown to result in sensory and sympathetic nervous sy stem deficits (Lee et al., 1992a,b). In order to establish precisely w hich subsets of neurons are capable of responding to neurotrophins (NT s) through the low-affinity NGF receptor, p75 was localized in the pri mate autonomic and somatic sensory nervous systems. In the autonomic s ystem, cell bodies of some parasympathetic and enteric neurons express ed detectable levels of p75, whereas all sympathetic neurons expressed the protein. In the sensory system, some, but not all, cell bodies we re labeled in cranial and spinal sensory ganglia and in the mesencepha lic nucleus. Some peripheral and central projections of the sensory ne urons were also labeled. Centrally, most of the labeled processes were found in regions containing primarily small unmyelinated fibers, incl uding lamina II of Rexed and areas of the solitary tract and nucleus. Peripherally, labeled processes were associated with unmyelinated nerv es and specialized structures such as taste buds and Meissner corpuscl es, but not with myelinated processes. This study indicates that the s ubset of neurons in the autonomic nervous system likely to be capable of responding to neurotrophins is broader than generally thought, and that p75-expressing neurons tend to be clustered. Moreover, in the sen sory nervous system p75 is expressed by most cell bodies, but expressi on in their projections is restricted both peripherally and centrally to unmyelinated processes and nerve terminals