Brain DA D2 receptors predict reinforcing effects of stimulants in humans: replication study.

We had shown that striatal DA D2 receptors levels predicted the reinforcing responses to the psychostimulant drug methylphenidate in nondrug-abusing subjects. Here, we assessed the replicability of this finding. We measured D2 receptors with PET and [(11)C]raclopride (twice to determine stability) in seven nondrug-abusing subjects to assess if they predicted the self-reports of "drug-liking" to intravenous methylphenidate (0.5 mg/kg). DA D2 measures were significantly correlated with "drug-liking" in both evaluations (r = 0.82 and r = 0.78); subjects with the lowest levels reported the higher ratings of "drug-liking" and vice versa. These results replicate our previous findings and provide further evidence that striatal DA D2 receptors modulate reinforcing responses to stimulants in humans and may underlie predisposition for drug self-administration.