The effects of nicotine on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced dopaminergic neuronal loss in the mouse substantia nigra pars compacta (SNpc). (A) Tyrosine hydroxylase-immunoreactive (TH-IR) neurons in the mouse SNpc. Scale bar: 250 μm. (B) Stereological cell counts of TH-IR neurons in the mouse SNpc. Data are presented as a percentage of controls (mean ± SEM) from four to six mice per group. **P < 0.01 versus the control (saline-only) group; ##
P < 0.01 versus the MPTP treatment group.