TAAR1 and Parkinson disease: The decrease of TAAR1 in olfactory-related brain regions may lead to olfactory dysfunction in MPTP-induced PD mice through several mechanisms: (1) Regulating cellular apoptosis: In spinal cord-injured rats, when TAAR1 was activated, the apoptosis in spinal motor neurons was inhibited, and the recovery of hindlimb motor functions was facilitated [63].