GRM1 and cerebellar ataxia: Antibodies to Homer-3 [22], PKCγ [10], mGluR1[12,38], and GluRδ2 [20,21], which have been described in occasional patients with cerebellar ataxia and are known to bind to PC somata and/or dendrites, were ruled out by double-labeling experiments employing mouse, rat, and monkey cerebellum tissue sections as well as by Western blot analysis (not shown).