TH and Parkinson disease: In the context of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced Parkinson’s disease (PD) in mice, the preservation of tyrosine hydroxylase (TH) immunoreactivities in the substantia nigra and dopamine transporter (DAT) immunoreactivities in the striatum, typically compromised by MPTP, was achieved through treatment with a combination of broad-spectrum antibiotics (ampicillin, metronidazole, and neomycin sulfate) (Pu et al., 2019; Fang et al., 2020; Varesi et al., 2022).