Effects of (S)-ketamine on striatal dopamine: a [11C]raclopride PET study of a model psychosis in humans (original) (raw)

2000, Journal of Psychiatric Research

Administration of the N-methyl-D-aspartate (NMDA) antagonist S-ketamine in normals produces a psychosis-like syndrome including several positive and negative symptoms of schizophrenic disorders (Abi-Saab WM, D'Souza DC, Moghaddam B, Krystal JH. The NMDA antagonist model for schizophrenia: promise and pitfalls. Pharmacopsychiatry 1998;31:104±109). Given the clinical ecacy of dopamine (DA) D2 receptor antagonists in the treatment of positive symptoms, it is conceivable that Sketamine-induced psychotic symptoms are partially due to a secondary activation of dopaminergic systems. To date, animal and human studies of the eects of NMDA antagonists on striatal DA levels have been inconsistent. The present study used positron emission tomography (PET) to determine whether a psychotomimetic dose of S-ketamine decreases the in vivo binding of [ 11 C]raclopride to striatal DA D2 receptors in humans (n = 8). S-ketamine elicited a psychosis-like syndrome, including alterations in mood, cognitive disturbances, hallucinations and ego-disorders. S-ketamine decreased [ 11 C]raclopride binding potential (BP) signi®cantly in the ventral striatum (À17.5%) followed by the caudate nucleus (À14.3%) and putamen (À13.6%), indicating an increase in striatal DA concentration. The change in raclopride BP in the ventral striatum correlated with heightened mood ranging from euphoria to grandiosity. These results provide evidence that the glutamatergic NMDA receptor may contribute to psychotic symptom formation via modulation of the DA system.