Nerve growth factor receptor immunoreactivity in non-nervous structures of the adult rat brain

The non-neuronal distribution of nerve growth factor receptors (NGFr) in the adult rat brain was investigated immunohistochemically using an anti-NGFr monoclonal antibody (192-IgG). In addition to the neurons known to be NGF-dependent or containing NGF binding-sites, a moderate to strong NGFr immunoreactivity was observed in several non-nervous tissues such as the ependymal cells, the epithelial cells of the choroid plexus, the leptomeninge and the cerebral blood vessels. Vascular immunoreactivity for NGFr occurs in the adventitia and muscular layers of the large arteries (circle of Willis) and, apparently, in all the wall layers of the intermediate or small (pial-arachnoid) arteries. The present results provide direct evidence for the presence of non-neuronal NGFr in the brain of adult rats, and suggest a possible involvement of NGF in roles other than those classically thought.