Presynaptic localization of a metabotropic glutamate receptor, mGluR7, in the primary afferent neurons: an immunohistochemical study in the rat.

An antibody which recognizes specifically a metabotropic glutamate receptor, mGluR7, was produced by using a trpE fusion protein containing a C-terminal sequence of rat mGluR7. Neuropil in laminae I and II of the dorsal horn of the rat, as well as many neuronal cell bodies in the dorsal root ganglion, showed mGluR7-like immunoreactivity; the immunoreactivity in neuropil was seen in axon terminals, which were filled with round synaptic vesicles and constituted axodendritic and axosomatic asymmetric synapses. The mGluR7-like immunoreactivity in laminae I and II in the dorsal horn was reduced after dorsal rhizotomy. The results indicate that some axon terminals of the primary afferent fibers to laminae I and II of the dorsal horn are provided with mGluR7.