TH and Parkinson disease: Meanwhile, the IF results showed that MPTP induction reduced the number of tyrosine hydroxylase (TH)‐positive neurons in the substantia nigra of PD mice, which would be alleviated by the treatments of EcN‐GLP‐1, exenatide, and EcN, with EcN‐GLP‐1 being the most efficient one (Figure 3b and f).