HRH4 and Parkinson disease: Moreover, the H4R mRNA levels in the SN showed a significant increase both in PD patients and rotenone‐induced PD models, and the intracerebellar administration of JNJ 7777120 decreased the pro‐inflammatory phenotype of microglia, reduced α‐synuclein accumulation in the SN and striatum, and attenuated the degeneration of SN dopaminergic neurons in PD model rats [31].