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.