GLUTAMATE TRANSPORTER MESSENGER-RNA AND GLUTAMATE-LIKE IMMUNOREACTIVITY IN SPINAL MOTONEURONS

GLUTAMATE is the major excitatory neurotransmitter in the central nerv ous system. The release of glutamate is terminated by rapid uptake of glutamate into the presynaptic nerve terminals and into surrounding gl ial cells. Recently, a neuronal glutamate transporter was cloned from rabbit small intestine, thereby providing the possibility to study the distribution of cells that express glutamate transporter mRNA. Using oligonucleotide probes and in situ hybridization, glutamate transporte r mRNA was demonstrated in large cell bodies, presumably motoneurones, in the thoracic spinal cord of the rabbit. Immunohistochemical analys is with rabbit polyclonal antibodies to glutamate showed immunoreactiv ity in the cytoplasm of large cell bodies in the ventral horn, presuma bly motoneurones, of the rat spinal cord. Glutamate-LI was in addition demonstrated in the motor end plate in hindlimb muscle of the rat, as visualized by double-labelling with mouse monoclonal antibodies to sy naptophysin. Taken together, these data raise the possibility that glu tamate has a function at the vertebrate neuromuscular junction.