Previous pharmacokinetics and electrophysiological results indicated an important role of nicotine in the modulation of dopamine transporter (DAT). To elucidate the expression changes of DAT on chronic nicotine and smoke administration, the effects of nicotine and passive cigarette smoke on DAT mRNA expression in the ventral tegmental area (VTA) and the substantia nigra (SN) area were examined using in situ hybridization and RNase protection assay. The results showed that chronic nicotine and smoke exposure highly unregulated DAT mRNA in the VTA and SN areas, including the dorsal part of substantia nigra pars compacta. Smoke for 30 min showed the highest increasing effect, whereas nicotine and smoke for 10 min only had slightly increasing effects. However, smoke for 1 h showed an increasing effect to a lesser extent than 30 min. These results revealed a new aspect of nicotine's modulation on the DAT, and may have important roles in neuropsychological disorders related to the midbrain abnormalities such as drugs addiction.