EVIDENCE THAT PERIHYPOGLOSSAL NEURONS INVOLVED IN VESTIBULAR-AUDITORYAND GAZE CONTROL FUNCTIONS RESPOND TO NERVE GROWTH-FACTOR

Nerve growth factor (NGF), which has long been considered to be a trop hic factor for peripheral sensory and sympathetic neurons, has been fo und recently to influence cholinergic neurons in the basal forebrain a nd neostriatum. In the present study, we provide evidence that brainst em neurons in the perihypoglossal area that relay information from the inner ear and vestibular apparatus to the cerebellum and tectum are r esponsive to NGF. These neurons, which are located in the nucleus prep ositus hypoglossi (NPH), spinal vestibular nucleus, cochlear complex, and gigantocellular and paragigantocellular nuclei of the reticular fo rmation, express functional receptors for NGF and up-regulate the expr ession of trkA receptors after injection of NGF into targets. In addit ion, the developmental up-regulation of NGF in the cerebellum coincide s with the differentiation of the perihypoglossal nuclei. These result s suggest that neurons representing the principal brain relays for aud itory and vestibular pathways and perihypoglossal neurons involved in gaze coordination are a novel group of central neurons (besides cholin ergic neurons in the basal forebrain and neostriatum) that respond to NGF. (C) 1997 Wiley-Liss, Inc.