PET STUDIES OF THE PRESYNAPTIC AND POSTSYNAPTIC DOPAMINERGIC SYSTEM IN TOURETTES-SYNDROME

Dysfunction of the dopaminergic pathway has been postulated to underli e the symptomatology of Tourette's syndrome. Presynaptic functional in tegrity of dopaminergic terminals was assessed with F-18-dopa PET in 1 0 patients with Tourette's syndrome, three of whom were drug free and seven of whom were on neuroleptic treatment. Dopamine D-2 receptor sit e density was measured with C-11-raclopride PET in a further group of five drug free patients with Tourette's syndrome. Mean caudate and put amen F-18-dopa influx constants were similar in patients with Tourette 's syndrome and controls, and there was no difference in F-18-dopa upt ake between the and untreated Tourette's syndrome groups. Mean caudate and putamen C-11-raclopride binding potentials in patients with Toure tte's syndrome were also similar to control values. The findings sugge st that striatal metabolism of exogenous levodopa and the density of s triatal D-2 receptors are both normal in patients with Tourette's synd rome and that Tourette's syndrome does not arise fi om a primary dysfu nction of dopaminergic terminals.