Immunocytochemical localization of the mGluR1 alpha metabotropic glutamate receptor in the dorsal cochlear nucleus.

We demonstrate that the metabotropic glutamate receptor mGluR1 alpha is enriched in two interneuron cell populations in the dorsal division of the cochlear nucleus. Electron microscopic analysis confirms that mGluR1 alpha immunoreactivity is concentrated in the dendritic spines of cartwheel cells and in dendrites of the recently described unipolar brush cells. The cartwheel cells, which have many similarities to the Purkinje cells of the cerebellum, participate in a local neuronal circuit that modulates the output of the dorsal cochlear nucleus. Immunostained unipolar brush cells were observed in granule cell regions of the cochlear nucleus and the vestibulocerebellum. The presence of analogous cell types with similar patterns of immunolabeling in the cerebellum and in the dorsal cochlear nucleus suggests that a shared but as yet unknown mode of processing may occur in both structures.