GRM1 and Ataxia: However, the term PACA should not be used if such neuronal antibodies have already been shown to be directly involved in the pathogenesis of the ataxia (e.g. DPPX, mGluR1, GABABR, anti-GAD) or are markers of ataxias with a known trigger (e.g. anti-Yo in PCD or antigliadin antibodies in GA).