The up-regulation of metabotropic glutamate receptor 5 (mGluR5) in Down's syndrome brains

We investigated the expression of metabotropic glutamate receptor 5 (mGluR5), a subtype of group I mGluRs, in the cerebral cortex of cases with Down's syndrome (DS), using immunohistochemistry and immunoblotting with this receptor. The up-regulation of mGluR5 was observed in DS by immunohistochemistry, and atrophic pyramidal neurons were immunolabelled in elderly DS cases. Western blotting confirmed the increased expression in DS brains. Since group I mGluR regulates the metabolism of amyloid precursor protein (APP) and accelerates its processing into non-amyloidogenic APP, the overexpression of mGluR5 may be related to the pathological state of APP metabolism in DS.