Human metabotropic glutamate receptors, nucleic acids encoding same and uses thereof

A screening assay for identifying an agonist or antagonist for any metabotropic glutamate receptor mediated activity associated therewith in a test cell, said test cell containing a cyclic nucleotide gated channel and expressing a glutamate receptor on its cell surface, said assay comprising the steps of:

• (a) introducing a nucleic acid comprising a sequence of nucleotides encoding a metabotropic glutamate receptor subtype into said test cell under conditions favoring expression of said glutamate receptor subtype in said test cell, wherein said glutamate receptor is characterized as being able to influence cyclic nucleotide levels in said test cell;
• (b) contacting said compound with said test cell;
• (c) measuring changes in the amount of cyclic nucleotide activation of said cyclic nucleotide gated channel in the presence and absence of the agonist or antagonist, thereby measuring changes in the amount of cyclic nucleotides in said test cell, wherein a change in the amount of cyclic nucleotides in said test cell in the presence of said agonist or antagonist, compared to the absence of said agonist or antagonist, indicates modulation of said glutamate receptor by said agonist or antagonist;
• and
• (d) wherein in the absence of said glutamate receptor, or cyclic nucleotide-gated channel, no response to the agonist or antagonist is observed.