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Methylphenidate hydrochloride (MP) is an effective treatment for attention-deficit/hyperactivity disorder (ADHD), a common neurobehavioral disorder of childhood onset characterized by inattention, hyperactivity, and distractibility. Methylphenidate hydrochloride blocks the dopamine transporters (DAT), the main mechanism for removing dopamine (DA) from the(More)
Prior research points to the importance of psychostimulants in improving self-control. However, the neural substrates underlying such improvement remain unclear. Here, in a pharmacological functional MRI study of the stop signal task, we show that methylphenidate (as compared with placebo) robustly decreased stop signal reaction time (SSRT), an index of(More)
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(More)
Dopamine's role in inhibitory control is well recognized and its disruption may contribute to behavioral disorders of discontrol such as obesity. However, the mechanism by which impaired dopamine neurotransmission interferes with inhibitory control is poorly understood. We had previously documented a reduction in dopamine D2 receptors in morbidly obese(More)
BACKGROUND Attention-deficit/hyperactivity disorder is a psychiatric disorder that starts in childhood. The mechanism of action of methylphenidate, the most common treatment for attention deficit hyperactivity disorder, is unclear. In vitro, the affinity of methylphenidate for the norepinephrine transporter (NET) is higher than that for the dopamine(More)
[(11)C]P943 is a new radioligand recently developed to image and quantify serotonin 5-Hydroxytryptamine (5-HT(1B)) receptors with positron emission tomography (PET). The purpose of this study was to evaluate [(11)C]P943 for this application in humans, and to determine the most suitable quantification method. Positron emission tomography data and arterial(More)
Tourette syndrome (TS) is characterized by tics, sensorimotor gating deficiencies, and abnormalities of cortico-basal ganglia circuits. A mutation in histidine decarboxylase (Hdc), the key enzyme for the biosynthesis of histamine (HA), has been implicated as a rare genetic cause. Hdc knockout mice exhibited potentiated tic-like stereotypies, recapitulating(More)
The drive for food is one of the most powerful of human and animal behaviors. Dopamine, a neurotransmitter involved with motivation and reward, its believed to regulate food intake in laboratory animals by modulating its rewarding effects through the nucleus accumbens (NA). Here we assess the involvement of dopamine in "nonhedonic" food motivation in(More)
Drugs of abuse are rewarding to addicted and nonaddicted subjects, but they trigger craving and compulsive intake only in addicted subjects. Here, we used positron emission tomography (PET) and [18F] deoxyglucose to compare the brain metabolic responses (marker of brain function) of cocaine-addicted subjects (n = 21) and controls (n = 15) to identify brain(More)
Methylphenidate (Ritalin) is an effective drug in the treatment of attention deficit hyperactivity disorder. However, the doses required therapeutically vary significantly between subjects and it is not understood what determines these differences. Since methylphenidate's therapeutic effects are in part due to increases in extracellular DA secondary to(More)