D-2 receptor binding in dopa-responsive dystonia

We have studied dopamine D-2 receptor binding by [C-11]raclopride positron emission tomography in 14 patients with dopa-responsive dystonia (DRD). Data were compared with 16 levodopa-treated patients with Parkinson's disease (PD) and 26 healthy controls. The results revealed an elevated [C-11]raclopride binding index in the putamen and caudate nucleus of DRD patients compared with controls as well as a significant elevation in the caudate nucleus compared with PD patients. The increase of [C-11]raclopride binding may be interpreted either as reduced tracer displacement by endogenous dopamine, or as an alteration of the receptor features due to chronic dopamine deficiency. The difference in [C-11]raclopride binding in DRD and PD patients in the caudate nucleus suggests that this structure may be of pathophysiological relevance in the presentation of the clinical features of both diseases.