The effects of dopaminergic D2 stimulation and blockade on smoking behavior.

Researchers have hypothesized that dopamine mediates the reinforcing effects of stimulant drugs, including nicotine. Three experiments tested whether manipulating dopamine would alter human smoking behavior. Experiments used double-blind, repeated measures designs. In Experiment 1, 4 participants were given haloperidol (a dopamine antagonist; placebo, 0.5, and 1.0 mg) on 3 occasions. The smoking rate was faster in the 1.0 mg versus the placebo condition. In Experiment 2, 12 participants were given haloperidol (2.0 mg) and placebo on 2 occasions. The intercigarette interval was shorter at the expected time of peak drug concentration. In Experiment 3, 5 participants were given bromocriptine (a dopamine agonist, 2.5 mg) and placebo on 2 occasions. The smoking rate was significantly slower with bromocriptine. These results suggest that blockade of D2 receptors increases smoking whereas their stimulation decreases smoking.