DRD2 and Parkinson disease: Hence, it could be postulated that the relevance of GPR37 in PD could be related to its interaction with striatal A2AR and/or D2R. Supporting this idea, we recently reported that GPR37−/− mice showed lower haloperidol-induced catalepsy18, thus suggesting an altered functioning of postsynaptic striatal D2R20 in GPR37−/− mice.