NEUROTRANSMITTER RECEPTORS AND VOLTAGE-DEPENDENT CA2-RNA FROM THE ADULT CORPUS-CALLOSUM( CHANNELS ENCODED BY MESSENGER)

The presence of mRNAs encoding neurotransmitter receptors and voltage- gated channels in the adult human and bovine corpus callosum was inves tigated using Xenopus oocytes. Oocytes injected with mRNA extracted fr om the corpus callosum expressed functional receptors to glutamate, ac etylcholine, and serotonin, and also voltage-operated Ca2+ channels, a ll with similar properties in the two species studied. Acetylcholine a nd serotonin elicited oscillatory Cl- currents due to activation of th e inositol phosphate-Ca2+ receptor-channel coupling system. Glutamate and its analogs N-methyl-D-aspartate (NMDA), kainate, quisqualate, and lpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) induce d smooth currents. The non-NMDA responses showed a strong inward recti fication at positive potentials and were potently blocked by 6,7-dinit roquinoxaline-2,3-dione, as observed for the AMPA/kainate glutamate re ceptors GLUR1 and GLUR3. Furthermore, in situ hybridization experiment s showed that GLUR1 and GLUR3 mRNAs are present in corpus callosum cel ls that were labeled with antiserum to glial fibrillary acid protein a nd that, in primary cell cultures, had the morphology of type 2 astroc ytes. These results indicate that glial cells in the adult corpus call osum possess mRNA encoding functional neurotransmitter receptors and C a2+ channels. These molecules may provide a mechanism for glial-neuron al interactions.