GRM5 and Huntington disease: The signalling of mGlu5 is altered in neuronal cultures and brain slices from pre-symptomatic HdhQ111/Q111 HD mice, with mGlu5 agonism leading to a reduction in mGlu5 -mediated IP3 formation due to an increase in PKC-mediated mGlu5 receptor desensitisation (Ribeiro et al., 2010).