GRM2 and schizophrenia: These include the blind-drunk (Bdr) mutant, a mutation in the synaptosomal-associated protein (Snap)-25, which results in impaired synaptic exocytosis [47]; and metabotropic glutamate receptor 2 and 3 double knockout mice (Grm2/3−/−), which lack presynaptic inhibitory autoreceptors which have been implicated in schizophrenia [48].