IMMUNOHISTOCHEMICAL LOCALIZATION OF MGLUR7 PROTEIN IN THE RODENT AND HUMAN CEREBELLAR CORTEX USING SUBTYPE-SPECIFIC ANTIBODIES

Metabotropic glutamate receptors (mGluRs) are a heterogeneous family o f G protein coupled receptors that are linked to multiple second messe nger systems to regulate neuronal excitability and synaptic transmissi on. To characterise the protein expression of the two mGluR7 receptor splice variants in human and rat cerebellar cortex, antibodies specifi c to mGluR7 were generated. Antibodies were raised against a glutathio ne-S-transferase fusion protein containing amino acid residues located in the extracellular domain common to both the human and rat mGluR7 s plice variants. These antibodies specifically detected human mGluR7a i n mammalian cells transfected with this receptor. In agreement with mG luR7 in situ hybridisation studies, immunohistochemistry performed at the light microscope level revealed that mGluR7 protein expression occ urred most prominently in a particular population of nerve cells commo n to both the human and rat, located within the cerebellar cortex of g ray matter contained within transverse folia. Moreover, strong mGluR7- like immunoreactivity was seen in Purkinje cell body cytoplasm of the Purkinje cell layer. In the most superficial cerebellar cortical layer , the molecular layer, immunostaining was observed in Purkinje cell as sociated proximal and distal dendritic trees. No detectable labelling was evident in intrinsic deep cerebellar nuclei known to contain GABAe rgic terminals of projecting Purkinje cell axons. These data are sugge stive of a post-synaptic location of mGluR7 in this central nervous sy stem structure. In the rodent, additional non-Purkinje cells thought t o represent inhibitory interneurones were labelled at all levels in th e molecular layer. mGluR7-like immunoreactivity was not associated wit h glial cells. (C) 1998 Elsevier Science B.V. All rights reserved.