Unipolar brush cells in the cochlear nuclei of a primate (Callithrix jacchus).

Unipolar brush cells (UBCs) have been recognized in the cerebella of many species including primates. They have also been identified in the cochlear nuclei (CN) of many mammals, however, not in any primate. Our immunohistochemical study in the marmoset demonstrates the presence of abundant calretinin immunoreactive (CR-ir) UBCs in the cerebellum, as in other mammals. In the marmoset CN, in contrast, CR-ir UBCs could hardly be identified. The reverse pattern was evident in sections immunostained for a metabotropic glutamate receptor (mGluR2/3-IR): beautifully stained UBCs were present in the CN, but the stained cerebellar structures were difficult to identify as UBCs. The present findings indicate that UBCs are present in the CN of primates, as in other mammals, but that cerebellar and CN UBCs might differ in their molecular equipment in primates.