GRM1 and arthritic joint disease: An mGluR1 NAM (CPCCOEt) administered stereotaxically into the CeA reduced the evoked responses of CeA neurons in the arthritis pain state, while an mGluR5 NAM (MPEP) had inhibitory properties in both normal and pain conditions, providing evidence for a change of mGluR1 function in pain [87].