Upregulation of putaminal dopamine D-2 receptors in early Parkinson's disease: A comparative PET study with [C-11]raclopride and [C-11]N-methylspiperone

: Kaasinen V, Ruottinen HM, Nagren K, Lehikoinen P, Oikonen T, Rinne JO

Publisher: SOC NUCLEAR MEDICINE INC

: 2000

: Journal of Nuclear Medicine

: JOURNAL OF NUCLEAR MEDICINE

: J NUCL MED

: 41

: 1

: 65

: 70

: 6

: 0161-5505

Dopamine D-2 receptor function was assessed in a PET study with 2 dopamine D-2 receptor PET ligands, [C-11]raclopride (RAG) and [C-11]N-methylspiperone (NMSP), in early Parkinson's disease. Methods: Seven patients with early Parkinson's disease and 5 healthy volunteers were studied. Each underwent PET both with reversible [C-11]RAC and with irreversible [C-11]NMSP. Results: Upregulation of dopamine D-2 receptors in the putamen contralateral to the predominant symptoms of Parkinson's disease was confirmed using both [C-11]RAC and [C-11]NMSP. Uptake of [C-11]RAC in the contralateral putamen was 105% of uptake in the opposite putamen (P = 0.020). For [C-11]NMSP, uptake in the contralateral putamen was 105% of uptake in the ipsilateral putamen (P = 0.011). No significant differences between Parkinson's disease patients and healthy volunteers were detected in any of the studied brain regions using either [C-11]RAC or [C-11]NMSP. No significant differences between [C-11]RAC and [C-11]NMSP uptake were detected in the striatum, whereas in the extrastriatal regions, [C-11]NMSP showed significantly higher uptake than [C-11]RAC both in healthy volunteers and in Parkinson's disease patients. Conclusion: This study confirms an increase in dopamine D-2 receptors in the putamen contralateral to the predominant symptoms, compared with the ipsilateral putamen, in early Parkinson's disease. This increase was seen both with reversible ligand [C-11]RAC and with irreversible ligand [C-11]NMSP and thus does not seem a consequence of depleted endogenous dopamine.