TH and Parkinson disease: Upon confirming a rat model for PD, 6-OHDA-lesioned rats were compared to 6-OHDA-lesioned rats treated with GP-EX for 28 days starting at day 3 after 6-OHDA lesioning and the quantities of TH-related immunoreactive survival cells and the levels of dopamine, DOPAC, HVA and norepinephrine in the substantia nigra and striatum were investigated.