Parasagittal compartmentalization of the metabotropic glutamate receptor mGluR1b in the cerebellar cortex

The parasagittal distribution of the splice variant 1b of the metabotropic glutamate receptor 1 (mGluR1b) was studied in the cerebellar cortex by using a specific mGluR1b antiserum combined with immunocytochemical methods. In frontal cerebellar sections, the antibodies revealed alternating bands of immunopositive and immunonegative Purkinje cells in lobules I to X of the vermis. In these regions, the distribution of mGluR1b was complementary to longitudinal bands of Purkinje cells expressing Zebrin II. The width of the mGluR1b-positive bands decreased progressively in the rostro-caudal direction, contrary to the rostro-caudal increase in the width of the Zebrin-positive bands. In the hemispheres, mGluR1b-positive bands alternated with Zebrin II-immunopositive bands in the paravermal portions of Crus I and Crus II. MGluR1b and Zebrin II immunoreactivities often colocalized in other regions of the hemispheral lobules. The compartmentalization of mGluR1b suggests that adjacent Purkinje cells might respond differently depending on the presence of mGluR1b at parallel fiber-Purkinje cell synapses.