EXPRESSION OF THE AMPA-SELECTIVE RECEPTOR SUBUNITS IN THE VESTIBULAR NUCLEI OF THE CHINCHILLA

The distribution of the AMPA type glutamate receptor has been investig ated throughout the central nervous system; however, no detailed descr iption of its distribution is available in the vestibular nuclei. In t he present study, in situ hybridization histochemistry and immunohisto chemistry were used to localize the messenger RNAs and proteins of the AMPA-selective receptor subunits GluR1, GluR2, GluR3 and GluR4 in the vestibular nuclei of the chinchilla. Immunohistochemistry with subuni ts specific antisera showed differential distribution of the subunits in the vestibular nuclei. GluR2/3 antiserum labeled the most neurons, suggesting that many if not all vestibular neurons receive glutamaterg ic input. GluR1-positive neurons were fewer than GluR2/3 immunoreactiv e neurons and GluR4 immunoreactivity was found in the fewest number of neurons. GluR1 and GluR4 immunoreactivity was also found in astrocyte -like structures. In situ hybridization with S-35-labeled complementar y RNA probes confirmed the distribution of the AMPA receptor subunits obtained by immunohistochemistry. Quantitative analysis of the levels of hybridization showed a high degree of diversity in the levels of ex pression of the GluR2 subunit mRNA, with the highest levels of express ion in the giant Deiter's cells of the lateral vestibular nuclei and t he lowest levels in the small neurons throughout the vestibular nuclei . The subunit compositions of the AMPA receptors determine their physi ological properties. Differential distribution and levels of expressio n of the receptor subunits in the vestibular nuclei may be related to the characteristics of information processing through the vestibular s ystem.