Molecular and functional properties of metabotropic glutamate receptors in the brain

We examined the molecular structural and functional properties of metabotropic glutamate receptors (mGluRs) in rat brains, especially the subtypes 1 and 5 which are known to stimulate phosphoinositide (PI) metabolism. We found that mGluR5 as well as mGluR1 has structural variants, most likely derived by the alternative splicing of the gene. We also found that, under certain circumstances, mGluR1 could inhibit, instead of stimulate, PI turnover in a G protein-dependent manner. This finding may give a possible explanation for the discrepancy we observed between the postnatal development of glutamate-stimulated PI turnover and the postnatal ontogenesis of mGluRs.