Since spinophilin-KO mice present increased intracellular mGluR5 signalling [48] and this receptor has been implicated in the development of cocaine addiction [8, 28, 30, 66–68], we sought to investigate if a negative allosteric modulator for mGluR5 would interfere on cocaine effects in spinophilin-KO mice. This evidence concerns the gene GRM5 and cocaine dependence.