In vivo voltammetry was used to measure the clearance to exogenously applied dopamine (DA) in the nucleus accumbens following acute systemic nicotine administration in urethane-anesthetized rats. The IVEC-5 system was used for continuous in vivo electrochemical measurements. A finite amount of DA was pressure-ejected (25-100 nl, 200 microM barrel concentration) at 5-min intervals from micropipettes (tip diameter, 10-15 microns) positioned 250 +/- 50 microns from the recording electrode. The peak DA concentration after each DA ejection was significantly decreased in rats following nicotine, but not in rats given saline. In addition, when mecamylamine was administered 20 min before nicotine it clearly antagonized nicotine effects. These results suggest that nicotine may actually facilitate DA transporter systems within the nucleus accumbens.