CELLULAR AND SUBCELLULAR-LOCALIZATION OF THE MGLUR5A METABOTROPIC GLUTAMATE-RECEPTOR IN RAT SPINAL-CORD

THE cellular and subcellular distribution of the mGluR5a metabotropic glutamate receptor was studied in the spinal cord of the rat using an antibody raised against a mGluR5a-specific carboxy-terminal peptide. S trong mGluR5a-immunoreactivity (mGluRSa-ir) was found in the laminae I -II of the dorsal horn, which gradually decreased towards the deeper l ayers. At the electron microscopical level, mGluR5a-ir was present exc lusively in neuronal somata and dendrites. Immunometal labelling revea led that mGluR5a-ir is concentrated at the periphery of postsynaptic d ensities of asymmetrical synapses or localized extrasynaptically at de ndritic and somatic membranes. The mGluR5a-immunoreactive dendritic pr ofiles were often targeted by synaptic boutons with the morphological characteristics of C-fibre terminals. These observations provide evide nce for mGluR5a being involved in the nociceptive transmission at the dorsal horn.