Impact of pramipexole on MPTP-induced loss of TH-IR neurons. Low-power photomicrograph (20x) of the substantia nigra and ventral tegmental area of tissue sections stained for TH-IR from individual cases of 4 groups of mice: (A) Veh-Veh, (B) pramipexole -Veh, (C) Veh-MPTP (25 mg/kg sc., 4 times in 2 days at 8 h intervals), (D) pramipexole-MPTP. Note the marked depletion of TH-IR from the substantia nigra and considerably lesser impact in the ventral tegmental area following MPTP. Pramipexole pretreatment regimen provided complete protection (see D) from MPTP. Abbreviations: SNpc, substantia nigra pars compacta; VTA, ventral tegmental area.