P2RY13 and Spinocerebellar ataxia type 3: However, the evidence for glutamate-induced neurotoxicity (excitotoxicity) in SCA3 progression is largely derived from in vitro studies of cellular models and in vivo studies of SCA3 model animals [119,120,121,122], and few known biomarkers provide a rationale for such studies with the exception of those showing elevated intracellular calcium [113] due to altered expression of the adenosinergic receptor P2RY13 [36].